Imaging of Osteochondroma: Variants and Complications with Radiologic-Pathologic Correlation1
Mark D. Murphey, MD ,
James J. Choi, MD , 2,
Mark J. Kransdorf, MD,
Donald J. Flemming, CDR, MC, USN and
Frances H. Gannon, MD
1 From the Departments of Radiologic Pathology (M.D.M., J.J.C.) and Orthopedic Pathology (F.H.G.), Armed Forces Institute of Pathology, 6825 16th St NW, Bldg 54, Rm M-133A, Washington, DC 20306; the Departments of Radiology and Nuclear Medicine, Uniformed Services University of Health Sciences, Bethesda, Md (M.D.M.); the Department of Radiology, University of Maryland School of Medicine, Baltimore (M.D.M.); the Department of Radiology, National Naval Medical Center, Bethesda, Md (D.J.F.); and the Department of Radiology, Mayo Clinic, Jacksonville, Fla (M.J.K.). Received April 12, 2000; revision requested April 27 and received May 19; accepted May 19. Address correspondence to M.D.M. (e-mail: murphey@afip.osd.mil).
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Figure 1. Osteochondroma development. Diagram illustrates the normal long bone with the epiphysis (tan), epiphyseal plate (blue), and "cut back" zone of remodeling (yellow). Periosteal bone cuff or encoche of Ranvier (large arrowhead) is shown with herniation of a small amount of physeal tissue (small arrowhead). This tissue migrates into the metaphysis from patient growth (arrows). The intracortical location of this physeal tissue and subsequent growth results in osteochondroma formation.
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Figure 2. Photograph of a coronally sectioned specimen of an osteochondroma of the rib shows marrow (*) and cortical (arrowheads) continuity with the underlying parent bone. The lobulated hyaline cartilage cap (open arrow) is seen and is similar in appearance to the costal cartilage (solid arrow).
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Figure 3a. Resected solitary benign osteochondroma. (a, b) Photographs of coronally sectioned gross specimen (a) and coronally sectioned whole mount specimen (hematoxylin-eosin [H-E] stain) (b) show yellow marrow in the lesion (*) and blue hyaline cartilage cap (arrowheads). There is undulation of the hyaline cartilage that invaginates in several areas into the medullary component (straight arrows) of the osteochondroma. (c) Photomicrograph (original magnification, x250; H-E stain) reveals yellow marrow (*) and trabeculae (straight arrows) within the osteochondroma, the hyaline cartilage cap with columns of cartilage cells (arrowheads), and fibrous capsule or perichondrium (curved arrows in b and c).
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Figure 3b. Resected solitary benign osteochondroma. (a, b) Photographs of coronally sectioned gross specimen (a) and coronally sectioned whole mount specimen (hematoxylin-eosin [H-E] stain) (b) show yellow marrow in the lesion (*) and blue hyaline cartilage cap (arrowheads). There is undulation of the hyaline cartilage that invaginates in several areas into the medullary component (straight arrows) of the osteochondroma. (c) Photomicrograph (original magnification, x250; H-E stain) reveals yellow marrow (*) and trabeculae (straight arrows) within the osteochondroma, the hyaline cartilage cap with columns of cartilage cells (arrowheads), and fibrous capsule or perichondrium (curved arrows in b and c).
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Figure 3c. Resected solitary benign osteochondroma. (a, b) Photographs of coronally sectioned gross specimen (a) and coronally sectioned whole mount specimen (hematoxylin-eosin [H-E] stain) (b) show yellow marrow in the lesion (*) and blue hyaline cartilage cap (arrowheads). There is undulation of the hyaline cartilage that invaginates in several areas into the medullary component (straight arrows) of the osteochondroma. (c) Photomicrograph (original magnification, x250; H-E stain) reveals yellow marrow (*) and trabeculae (straight arrows) within the osteochondroma, the hyaline cartilage cap with columns of cartilage cells (arrowheads), and fibrous capsule or perichondrium (curved arrows in b and c).
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Figure 4a. Benign solitary osteochondroma of the tibia in a 15-year-old boy with lesion growth. (a) Initial lateral radiograph of the ankle shows pathognomonic features of osteochondroma with a lesion composed of cortical and medullary bone protruding from the underlying tibia (open arrow). The cortical (solid arrows) and medullary (*) continuity with the tibia was seen on radiographs only in the lateral projection. The cartilage cap is not mineralized and cannot be seen. (b-d) Axial MR images (repetition time msec/echo time msec = 600/16) obtained before (b) and after (c) intravenous administration of gadolinium-based contrast material also reveal the cortical (arrowheads) and marrow (*) continuity with the underlying bone and yellow marrow in the lesion. The hyaline cartilage cap is 3 cm thick (curved arrows), shows mild peripheral and septal contrast material enhancement (straight arrows), and becomes very high signal intensity on the sagittal short-inversion-time inversion recovery (3,000/17, 90 msec inversion time) MR image (d). (e) Lateral radiograph obtained 2 years later shows lesion growth and mineralization that simulate malignant transformation but represent only growth in the skeletally immature patient. (f) Bone scan demonstrates marked increased uptake of radionuclide. (g) Photograph of the sagittally sectioned specimen correlates with the imaging appearance, revealing yellow marrow (*) and the thick hyaline cartilage cap (arrows). Foci of mineralization (x) are also seen, as noted previously in the MR images (b-d).
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Figure 4b. Benign solitary osteochondroma of the tibia in a 15-year-old boy with lesion growth. (a) Initial lateral radiograph of the ankle shows pathognomonic features of osteochondroma with a lesion composed of cortical and medullary bone protruding from the underlying tibia (open arrow). The cortical (solid arrows) and medullary (*) continuity with the tibia was seen on radiographs only in the lateral projection. The cartilage cap is not mineralized and cannot be seen. (b-d) Axial MR images (repetition time msec/echo time msec = 600/16) obtained before (b) and after (c) intravenous administration of gadolinium-based contrast material also reveal the cortical (arrowheads) and marrow (*) continuity with the underlying bone and yellow marrow in the lesion. The hyaline cartilage cap is 3 cm thick (curved arrows), shows mild peripheral and septal contrast material enhancement (straight arrows), and becomes very high signal intensity on the sagittal short-inversion-time inversion recovery (3,000/17, 90 msec inversion time) MR image (d). (e) Lateral radiograph obtained 2 years later shows lesion growth and mineralization that simulate malignant transformation but represent only growth in the skeletally immature patient. (f) Bone scan demonstrates marked increased uptake of radionuclide. (g) Photograph of the sagittally sectioned specimen correlates with the imaging appearance, revealing yellow marrow (*) and the thick hyaline cartilage cap (arrows). Foci of mineralization (x) are also seen, as noted previously in the MR images (b-d).
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Figure 4c. Benign solitary osteochondroma of the tibia in a 15-year-old boy with lesion growth. (a) Initial lateral radiograph of the ankle shows pathognomonic features of osteochondroma with a lesion composed of cortical and medullary bone protruding from the underlying tibia (open arrow). The cortical (solid arrows) and medullary (*) continuity with the tibia was seen on radiographs only in the lateral projection. The cartilage cap is not mineralized and cannot be seen. (b-d) Axial MR images (repetition time msec/echo time msec = 600/16) obtained before (b) and after (c) intravenous administration of gadolinium-based contrast material also reveal the cortical (arrowheads) and marrow (*) continuity with the underlying bone and yellow marrow in the lesion. The hyaline cartilage cap is 3 cm thick (curved arrows), shows mild peripheral and septal contrast material enhancement (straight arrows), and becomes very high signal intensity on the sagittal short-inversion-time inversion recovery (3,000/17, 90 msec inversion time) MR image (d). (e) Lateral radiograph obtained 2 years later shows lesion growth and mineralization that simulate malignant transformation but represent only growth in the skeletally immature patient. (f) Bone scan demonstrates marked increased uptake of radionuclide. (g) Photograph of the sagittally sectioned specimen correlates with the imaging appearance, revealing yellow marrow (*) and the thick hyaline cartilage cap (arrows). Foci of mineralization (x) are also seen, as noted previously in the MR images (b-d).
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Figure 4d. Benign solitary osteochondroma of the tibia in a 15-year-old boy with lesion growth. (a) Initial lateral radiograph of the ankle shows pathognomonic features of osteochondroma with a lesion composed of cortical and medullary bone protruding from the underlying tibia (open arrow). The cortical (solid arrows) and medullary (*) continuity with the tibia was seen on radiographs only in the lateral projection. The cartilage cap is not mineralized and cannot be seen. (b-d) Axial MR images (repetition time msec/echo time msec = 600/16) obtained before (b) and after (c) intravenous administration of gadolinium-based contrast material also reveal the cortical (arrowheads) and marrow (*) continuity with the underlying bone and yellow marrow in the lesion. The hyaline cartilage cap is 3 cm thick (curved arrows), shows mild peripheral and septal contrast material enhancement (straight arrows), and becomes very high signal intensity on the sagittal short-inversion-time inversion recovery (3,000/17, 90 msec inversion time) MR image (d). (e) Lateral radiograph obtained 2 years later shows lesion growth and mineralization that simulate malignant transformation but represent only growth in the skeletally immature patient. (f) Bone scan demonstrates marked increased uptake of radionuclide. (g) Photograph of the sagittally sectioned specimen correlates with the imaging appearance, revealing yellow marrow (*) and the thick hyaline cartilage cap (arrows). Foci of mineralization (x) are also seen, as noted previously in the MR images (b-d).
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Figure 4e. Benign solitary osteochondroma of the tibia in a 15-year-old boy with lesion growth. (a) Initial lateral radiograph of the ankle shows pathognomonic features of osteochondroma with a lesion composed of cortical and medullary bone protruding from the underlying tibia (open arrow). The cortical (solid arrows) and medullary (*) continuity with the tibia was seen on radiographs only in the lateral projection. The cartilage cap is not mineralized and cannot be seen. (b-d) Axial MR images (repetition time msec/echo time msec = 600/16) obtained before (b) and after (c) intravenous administration of gadolinium-based contrast material also reveal the cortical (arrowheads) and marrow (*) continuity with the underlying bone and yellow marrow in the lesion. The hyaline cartilage cap is 3 cm thick (curved arrows), shows mild peripheral and septal contrast material enhancement (straight arrows), and becomes very high signal intensity on the sagittal short-inversion-time inversion recovery (3,000/17, 90 msec inversion time) MR image (d). (e) Lateral radiograph obtained 2 years later shows lesion growth and mineralization that simulate malignant transformation but represent only growth in the skeletally immature patient. (f) Bone scan demonstrates marked increased uptake of radionuclide. (g) Photograph of the sagittally sectioned specimen correlates with the imaging appearance, revealing yellow marrow (*) and the thick hyaline cartilage cap (arrows). Foci of mineralization (x) are also seen, as noted previously in the MR images (b-d).
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Figure 4f. Benign solitary osteochondroma of the tibia in a 15-year-old boy with lesion growth. (a) Initial lateral radiograph of the ankle shows pathognomonic features of osteochondroma with a lesion composed of cortical and medullary bone protruding from the underlying tibia (open arrow). The cortical (solid arrows) and medullary (*) continuity with the tibia was seen on radiographs only in the lateral projection. The cartilage cap is not mineralized and cannot be seen. (b-d) Axial MR images (repetition time msec/echo time msec = 600/16) obtained before (b) and after (c) intravenous administration of gadolinium-based contrast material also reveal the cortical (arrowheads) and marrow (*) continuity with the underlying bone and yellow marrow in the lesion. The hyaline cartilage cap is 3 cm thick (curved arrows), shows mild peripheral and septal contrast material enhancement (straight arrows), and becomes very high signal intensity on the sagittal short-inversion-time inversion recovery (3,000/17, 90 msec inversion time) MR image (d). (e) Lateral radiograph obtained 2 years later shows lesion growth and mineralization that simulate malignant transformation but represent only growth in the skeletally immature patient. (f) Bone scan demonstrates marked increased uptake of radionuclide. (g) Photograph of the sagittally sectioned specimen correlates with the imaging appearance, revealing yellow marrow (*) and the thick hyaline cartilage cap (arrows). Foci of mineralization (x) are also seen, as noted previously in the MR images (b-d).
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Figure 4g. Benign solitary osteochondroma of the tibia in a 15-year-old boy with lesion growth. (a) Initial lateral radiograph of the ankle shows pathognomonic features of osteochondroma with a lesion composed of cortical and medullary bone protruding from the underlying tibia (open arrow). The cortical (solid arrows) and medullary (*) continuity with the tibia was seen on radiographs only in the lateral projection. The cartilage cap is not mineralized and cannot be seen. (b-d) Axial MR images (repetition time msec/echo time msec = 600/16) obtained before (b) and after (c) intravenous administration of gadolinium-based contrast material also reveal the cortical (arrowheads) and marrow (*) continuity with the underlying bone and yellow marrow in the lesion. The hyaline cartilage cap is 3 cm thick (curved arrows), shows mild peripheral and septal contrast material enhancement (straight arrows), and becomes very high signal intensity on the sagittal short-inversion-time inversion recovery (3,000/17, 90 msec inversion time) MR image (d). (e) Lateral radiograph obtained 2 years later shows lesion growth and mineralization that simulate malignant transformation but represent only growth in the skeletally immature patient. (f) Bone scan demonstrates marked increased uptake of radionuclide. (g) Photograph of the sagittally sectioned specimen correlates with the imaging appearance, revealing yellow marrow (*) and the thick hyaline cartilage cap (arrows). Foci of mineralization (x) are also seen, as noted previously in the MR images (b-d).
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Figure 5a. Benign solitary sessile osteochondroma of the fibula in a 19-year-old man. (a-e) Radiograph (a), axial CT scans (bone [b] and soft-tissue [c] windows), and axial T1-weighted (500/20) (d) and T2-weighted (2,000/90) (e) MR images show the marrow and cortical continuity of an osteochondroma and underlying fibula (large arrowheads). The various degrees of maturity and calcification in the areas of enchondral mineralization cause a heterogeneous appearance on CT and MR images and can be seen in the photograph of the axially sectioned gross specimen (f). Mature areas of bone formation contain yellow marrow architecture (*). Areas of calcified cartilage show high attenuation on CT scans (solid arrows in b and c), are white in the gross specimen (curved arrows), but are very heterogeneous on T2-weighted MR images (low signal intensity with all pulse sequences in densely calcified areas [small arrowheads in d and e] versus higher signal intensity in areas with more prominent components of nonmineralized cartilage [solid arrows in e]). Nonmineralized hyaline cartilage cap (open arrows) is thin (1 cm) and has more fluid characteristic at CT and MR imaging, reflecting its high water content, and has a blue color on the gross specimen. It is more difficult to detect on the soft-tissue window CT scan (c) than with MR imaging.
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Figure 5b. Benign solitary sessile osteochondroma of the fibula in a 19-year-old man. (a-e) Radiograph (a), axial CT scans (bone [b] and soft-tissue [c] windows), and axial T1-weighted (500/20) (d) and T2-weighted (2,000/90) (e) MR images show the marrow and cortical continuity of an osteochondroma and underlying fibula (large arrowheads). The various degrees of maturity and calcification in the areas of enchondral mineralization cause a heterogeneous appearance on CT and MR images and can be seen in the photograph of the axially sectioned gross specimen (f). Mature areas of bone formation contain yellow marrow architecture (*). Areas of calcified cartilage show high attenuation on CT scans (solid arrows in b and c), are white in the gross specimen (curved arrows), but are very heterogeneous on T2-weighted MR images (low signal intensity with all pulse sequences in densely calcified areas [small arrowheads in d and e] versus higher signal intensity in areas with more prominent components of nonmineralized cartilage [solid arrows in e]). Nonmineralized hyaline cartilage cap (open arrows) is thin (1 cm) and has more fluid characteristic at CT and MR imaging, reflecting its high water content, and has a blue color on the gross specimen. It is more difficult to detect on the soft-tissue window CT scan (c) than with MR imaging.
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Figure 5c. Benign solitary sessile osteochondroma of the fibula in a 19-year-old man. (a-e) Radiograph (a), axial CT scans (bone [b] and soft-tissue [c] windows), and axial T1-weighted (500/20) (d) and T2-weighted (2,000/90) (e) MR images show the marrow and cortical continuity of an osteochondroma and underlying fibula (large arrowheads). The various degrees of maturity and calcification in the areas of enchondral mineralization cause a heterogeneous appearance on CT and MR images and can be seen in the photograph of the axially sectioned gross specimen (f). Mature areas of bone formation contain yellow marrow architecture (*). Areas of calcified cartilage show high attenuation on CT scans (solid arrows in b and c), are white in the gross specimen (curved arrows), but are very heterogeneous on T2-weighted MR images (low signal intensity with all pulse sequences in densely calcified areas [small arrowheads in d and e] versus higher signal intensity in areas with more prominent components of nonmineralized cartilage [solid arrows in e]). Nonmineralized hyaline cartilage cap (open arrows) is thin (1 cm) and has more fluid characteristic at CT and MR imaging, reflecting its high water content, and has a blue color on the gross specimen. It is more difficult to detect on the soft-tissue window CT scan (c) than with MR imaging.
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Figure 5d. Benign solitary sessile osteochondroma of the fibula in a 19-year-old man. (a-e) Radiograph (a), axial CT scans (bone [b] and soft-tissue [c] windows), and axial T1-weighted (500/20) (d) and T2-weighted (2,000/90) (e) MR images show the marrow and cortical continuity of an osteochondroma and underlying fibula (large arrowheads). The various degrees of maturity and calcification in the areas of enchondral mineralization cause a heterogeneous appearance on CT and MR images and can be seen in the photograph of the axially sectioned gross specimen (f). Mature areas of bone formation contain yellow marrow architecture (*). Areas of calcified cartilage show high attenuation on CT scans (solid arrows in b and c), are white in the gross specimen (curved arrows), but are very heterogeneous on T2-weighted MR images (low signal intensity with all pulse sequences in densely calcified areas [small arrowheads in d and e] versus higher signal intensity in areas with more prominent components of nonmineralized cartilage [solid arrows in e]). Nonmineralized hyaline cartilage cap (open arrows) is thin (1 cm) and has more fluid characteristic at CT and MR imaging, reflecting its high water content, and has a blue color on the gross specimen. It is more difficult to detect on the soft-tissue window CT scan (c) than with MR imaging.
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Figure 5e. Benign solitary sessile osteochondroma of the fibula in a 19-year-old man. (a-e) Radiograph (a), axial CT scans (bone [b] and soft-tissue [c] windows), and axial T1-weighted (500/20) (d) and T2-weighted (2,000/90) (e) MR images show the marrow and cortical continuity of an osteochondroma and underlying fibula (large arrowheads). The various degrees of maturity and calcification in the areas of enchondral mineralization cause a heterogeneous appearance on CT and MR images and can be seen in the photograph of the axially sectioned gross specimen (f). Mature areas of bone formation contain yellow marrow architecture (*). Areas of calcified cartilage show high attenuation on CT scans (solid arrows in b and c), are white in the gross specimen (curved arrows), but are very heterogeneous on T2-weighted MR images (low signal intensity with all pulse sequences in densely calcified areas [small arrowheads in d and e] versus higher signal intensity in areas with more prominent components of nonmineralized cartilage [solid arrows in e]). Nonmineralized hyaline cartilage cap (open arrows) is thin (1 cm) and has more fluid characteristic at CT and MR imaging, reflecting its high water content, and has a blue color on the gross specimen. It is more difficult to detect on the soft-tissue window CT scan (c) than with MR imaging.
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Figure 5f. Benign solitary sessile osteochondroma of the fibula in a 19-year-old man. (a-e) Radiograph (a), axial CT scans (bone [b] and soft-tissue [c] windows), and axial T1-weighted (500/20) (d) and T2-weighted (2,000/90) (e) MR images show the marrow and cortical continuity of an osteochondroma and underlying fibula (large arrowheads). The various degrees of maturity and calcification in the areas of enchondral mineralization cause a heterogeneous appearance on CT and MR images and can be seen in the photograph of the axially sectioned gross specimen (f). Mature areas of bone formation contain yellow marrow architecture (*). Areas of calcified cartilage show high attenuation on CT scans (solid arrows in b and c), are white in the gross specimen (curved arrows), but are very heterogeneous on T2-weighted MR images (low signal intensity with all pulse sequences in densely calcified areas [small arrowheads in d and e] versus higher signal intensity in areas with more prominent components of nonmineralized cartilage [solid arrows in e]). Nonmineralized hyaline cartilage cap (open arrows) is thin (1 cm) and has more fluid characteristic at CT and MR imaging, reflecting its high water content, and has a blue color on the gross specimen. It is more difficult to detect on the soft-tissue window CT scan (c) than with MR imaging.
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Figure 6a. Solitary benign pedunculated osteochondroma of the femur in a 22-year-old man with an associated fracture. (a) Radiograph of the knee reveals a pedunculated osteochondroma with marrow and cortical continuity to the underlying femur (arrowheads). The lesion points away from the knee joint and a lucent area at the base represents a fracture (arrow). (b) Sonogram shows posterior acoustic shadowing from the ossified lesion component and small thin hypoechoic hyaline cartilage cap (*), both of which are easily distinguished from the more superficial hyperechoic fat and muscle. (c) Photograph of the coronally sectioned whole-mount specimen (H-E stain) shows the cortex (open arrows), yellow marrow space (solid arrows), cartilage cap (*), and a portion of the healing fracture (arrowheads).
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Figure 6b. Solitary benign pedunculated osteochondroma of the femur in a 22-year-old man with an associated fracture. (a) Radiograph of the knee reveals a pedunculated osteochondroma with marrow and cortical continuity to the underlying femur (arrowheads). The lesion points away from the knee joint and a lucent area at the base represents a fracture (arrow). (b) Sonogram shows posterior acoustic shadowing from the ossified lesion component and small thin hypoechoic hyaline cartilage cap (*), both of which are easily distinguished from the more superficial hyperechoic fat and muscle. (c) Photograph of the coronally sectioned whole-mount specimen (H-E stain) shows the cortex (open arrows), yellow marrow space (solid arrows), cartilage cap (*), and a portion of the healing fracture (arrowheads).
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Figure 6c. Solitary benign pedunculated osteochondroma of the femur in a 22-year-old man with an associated fracture. (a) Radiograph of the knee reveals a pedunculated osteochondroma with marrow and cortical continuity to the underlying femur (arrowheads). The lesion points away from the knee joint and a lucent area at the base represents a fracture (arrow). (b) Sonogram shows posterior acoustic shadowing from the ossified lesion component and small thin hypoechoic hyaline cartilage cap (*), both of which are easily distinguished from the more superficial hyperechoic fat and muscle. (c) Photograph of the coronally sectioned whole-mount specimen (H-E stain) shows the cortex (open arrows), yellow marrow space (solid arrows), cartilage cap (*), and a portion of the healing fracture (arrowheads).
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Figure 7a. Solitary benign osteochondroma of the pelvis in a 70-year-old man with vague hip pain. (a) Pelvic radiograph shows nonspecific sclerosis over the right supraacetabular region (arrow). Bone scan (not shown) revealed only mild radionuclide uptake. (b) CT scan reveals an osteochondroma with characteristic marrow (*) and cortical (arrowheads) continuity. The overlying soft-tissue attenuation could simulate a thick nonmineralized cartilage cap (arrows) and the possibility of malignant transformation. However, this finding represents iliacus muscle draped over the osteochondroma rather than a cartilage cap. (c) Photograph of a coronally sectioned whole-mount specimen reveals the cortical (solid arrows) and medullary (*) continuity with the underlying parent bone and lack of significant cartilage cap (open arrow).
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Figure 7b. Solitary benign osteochondroma of the pelvis in a 70-year-old man with vague hip pain. (a) Pelvic radiograph shows nonspecific sclerosis over the right supraacetabular region (arrow). Bone scan (not shown) revealed only mild radionuclide uptake. (b) CT scan reveals an osteochondroma with characteristic marrow (*) and cortical (arrowheads) continuity. The overlying soft-tissue attenuation could simulate a thick nonmineralized cartilage cap (arrows) and the possibility of malignant transformation. However, this finding represents iliacus muscle draped over the osteochondroma rather than a cartilage cap. (c) Photograph of a coronally sectioned whole-mount specimen reveals the cortical (solid arrows) and medullary (*) continuity with the underlying parent bone and lack of significant cartilage cap (open arrow).
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Figure 7c. Solitary benign osteochondroma of the pelvis in a 70-year-old man with vague hip pain. (a) Pelvic radiograph shows nonspecific sclerosis over the right supraacetabular region (arrow). Bone scan (not shown) revealed only mild radionuclide uptake. (b) CT scan reveals an osteochondroma with characteristic marrow (*) and cortical (arrowheads) continuity. The overlying soft-tissue attenuation could simulate a thick nonmineralized cartilage cap (arrows) and the possibility of malignant transformation. However, this finding represents iliacus muscle draped over the osteochondroma rather than a cartilage cap. (c) Photograph of a coronally sectioned whole-mount specimen reveals the cortical (solid arrows) and medullary (*) continuity with the underlying parent bone and lack of significant cartilage cap (open arrow).
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Figure 8a. Manifestations of HME in three patients. (a) Photograph of a 30-year-old patient with HME demonstrates marked forearm abnormalities and milder knee and ankle valgus deformities that result in a mild short stature. (b-d) Pelvic (b), lower extremity (c), and hand (d) radiographs of an 8-year-old patient show extensive undertubulation with widened metaphyses (Erlenmeyer flask deformity). These growth disturbances are much more apparent than the pelvic osteochondromas. Coxa and genu valgus, lateral ankle tilt (arrowhead), extrinsic erosion of the left fibula by the tibial osteochondroma (straight arrow), and osseous bowing of the radius with pseudo-Madelung (curved arrow) deformities are also seen. (e) Photograph of a coronally sectioned whole-mount specimen (H-E stain) from a 9-year-old patient reveals multiple osteochondromas involving the femur. The largest lesion medially shows characteristic medullary and cortical continuity (solid arrows) with the underlying parent bone as well as the overlying hyaline cartilage cap and perichondrium (open arrow). Yellow marrow within the lesion (M), undertubulation of bone with Erlenmeyer flask deformity (*), and multiple smaller lesions (arrowheads) are also seen.
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Figure 8b. Manifestations of HME in three patients. (a) Photograph of a 30-year-old patient with HME demonstrates marked forearm abnormalities and milder knee and ankle valgus deformities that result in a mild short stature. (b-d) Pelvic (b), lower extremity (c), and hand (d) radiographs of an 8-year-old patient show extensive undertubulation with widened metaphyses (Erlenmeyer flask deformity). These growth disturbances are much more apparent than the pelvic osteochondromas. Coxa and genu valgus, lateral ankle tilt (arrowhead), extrinsic erosion of the left fibula by the tibial osteochondroma (straight arrow), and osseous bowing of the radius with pseudo-Madelung (curved arrow) deformities are also seen. (e) Photograph of a coronally sectioned whole-mount specimen (H-E stain) from a 9-year-old patient reveals multiple osteochondromas involving the femur. The largest lesion medially shows characteristic medullary and cortical continuity (solid arrows) with the underlying parent bone as well as the overlying hyaline cartilage cap and perichondrium (open arrow). Yellow marrow within the lesion (M), undertubulation of bone with Erlenmeyer flask deformity (*), and multiple smaller lesions (arrowheads) are also seen.
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Figure 8c. Manifestations of HME in three patients. (a) Photograph of a 30-year-old patient with HME demonstrates marked forearm abnormalities and milder knee and ankle valgus deformities that result in a mild short stature. (b-d) Pelvic (b), lower extremity (c), and hand (d) radiographs of an 8-year-old patient show extensive undertubulation with widened metaphyses (Erlenmeyer flask deformity). These growth disturbances are much more apparent than the pelvic osteochondromas. Coxa and genu valgus, lateral ankle tilt (arrowhead), extrinsic erosion of the left fibula by the tibial osteochondroma (straight arrow), and osseous bowing of the radius with pseudo-Madelung (curved arrow) deformities are also seen. (e) Photograph of a coronally sectioned whole-mount specimen (H-E stain) from a 9-year-old patient reveals multiple osteochondromas involving the femur. The largest lesion medially shows characteristic medullary and cortical continuity (solid arrows) with the underlying parent bone as well as the overlying hyaline cartilage cap and perichondrium (open arrow). Yellow marrow within the lesion (M), undertubulation of bone with Erlenmeyer flask deformity (*), and multiple smaller lesions (arrowheads) are also seen.
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Figure 8d. Manifestations of HME in three patients. (a) Photograph of a 30-year-old patient with HME demonstrates marked forearm abnormalities and milder knee and ankle valgus deformities that result in a mild short stature. (b-d) Pelvic (b), lower extremity (c), and hand (d) radiographs of an 8-year-old patient show extensive undertubulation with widened metaphyses (Erlenmeyer flask deformity). These growth disturbances are much more apparent than the pelvic osteochondromas. Coxa and genu valgus, lateral ankle tilt (arrowhead), extrinsic erosion of the left fibula by the tibial osteochondroma (straight arrow), and osseous bowing of the radius with pseudo-Madelung (curved arrow) deformities are also seen. (e) Photograph of a coronally sectioned whole-mount specimen (H-E stain) from a 9-year-old patient reveals multiple osteochondromas involving the femur. The largest lesion medially shows characteristic medullary and cortical continuity (solid arrows) with the underlying parent bone as well as the overlying hyaline cartilage cap and perichondrium (open arrow). Yellow marrow within the lesion (M), undertubulation of bone with Erlenmeyer flask deformity (*), and multiple smaller lesions (arrowheads) are also seen.
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Figure 8e. Manifestations of HME in three patients. (a) Photograph of a 30-year-old patient with HME demonstrates marked forearm abnormalities and milder knee and ankle valgus deformities that result in a mild short stature. (b-d) Pelvic (b), lower extremity (c), and hand (d) radiographs of an 8-year-old patient show extensive undertubulation with widened metaphyses (Erlenmeyer flask deformity). These growth disturbances are much more apparent than the pelvic osteochondromas. Coxa and genu valgus, lateral ankle tilt (arrowhead), extrinsic erosion of the left fibula by the tibial osteochondroma (straight arrow), and osseous bowing of the radius with pseudo-Madelung (curved arrow) deformities are also seen. (e) Photograph of a coronally sectioned whole-mount specimen (H-E stain) from a 9-year-old patient reveals multiple osteochondromas involving the femur. The largest lesion medially shows characteristic medullary and cortical continuity (solid arrows) with the underlying parent bone as well as the overlying hyaline cartilage cap and perichondrium (open arrow). Yellow marrow within the lesion (M), undertubulation of bone with Erlenmeyer flask deformity (*), and multiple smaller lesions (arrowheads) are also seen.
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Figure 9a. Solitary benign osteochondroma with a popliteal pseudoaneurysm in a 13-year-old boy. Axial fat-suppressed gadolinium-enhanced T1-weighted (800/17) (a) and sagittal T2-weighted (5,000/120) (b) MR images and contrast material-enhanced axial CT scan (c) with sagittal reconstruction (d) show an osteochondroma containing yellow marrow and continuity with the underlying femur (large arrowheads). The large complex mass posterior to the osteochondroma (*) and containing the popliteal artery (arrow) just below the adductor canal represents a pseudoaneurysm. The pseudoaneurysm does not diffusely enhance with contrast material owing to thrombus as suggested by the concentric rings (small arrowheads) on the T2-weighted MR image (b). (Courtesy of Sergio Brincas, MD, Hospital de Caridade, Florianopolis, Brazil.)
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Figure 9b. Solitary benign osteochondroma with a popliteal pseudoaneurysm in a 13-year-old boy. Axial fat-suppressed gadolinium-enhanced T1-weighted (800/17) (a) and sagittal T2-weighted (5,000/120) (b) MR images and contrast material-enhanced axial CT scan (c) with sagittal reconstruction (d) show an osteochondroma containing yellow marrow and continuity with the underlying femur (large arrowheads). The large complex mass posterior to the osteochondroma (*) and containing the popliteal artery (arrow) just below the adductor canal represents a pseudoaneurysm. The pseudoaneurysm does not diffusely enhance with contrast material owing to thrombus as suggested by the concentric rings (small arrowheads) on the T2-weighted MR image (b). (Courtesy of Sergio Brincas, MD, Hospital de Caridade, Florianopolis, Brazil.)
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Figure 9c. Solitary benign osteochondroma with a popliteal pseudoaneurysm in a 13-year-old boy. Axial fat-suppressed gadolinium-enhanced T1-weighted (800/17) (a) and sagittal T2-weighted (5,000/120) (b) MR images and contrast material-enhanced axial CT scan (c) with sagittal reconstruction (d) show an osteochondroma containing yellow marrow and continuity with the underlying femur (large arrowheads). The large complex mass posterior to the osteochondroma (*) and containing the popliteal artery (arrow) just below the adductor canal represents a pseudoaneurysm. The pseudoaneurysm does not diffusely enhance with contrast material owing to thrombus as suggested by the concentric rings (small arrowheads) on the T2-weighted MR image (b). (Courtesy of Sergio Brincas, MD, Hospital de Caridade, Florianopolis, Brazil.)
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Figure 9d. Solitary benign osteochondroma with a popliteal pseudoaneurysm in a 13-year-old boy. Axial fat-suppressed gadolinium-enhanced T1-weighted (800/17) (a) and sagittal T2-weighted (5,000/120) (b) MR images and contrast material-enhanced axial CT scan (c) with sagittal reconstruction (d) show an osteochondroma containing yellow marrow and continuity with the underlying femur (large arrowheads). The large complex mass posterior to the osteochondroma (*) and containing the popliteal artery (arrow) just below the adductor canal represents a pseudoaneurysm. The pseudoaneurysm does not diffusely enhance with contrast material owing to thrombus as suggested by the concentric rings (small arrowheads) on the T2-weighted MR image (b). (Courtesy of Sergio Brincas, MD, Hospital de Caridade, Florianopolis, Brazil.)
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Figure 10a. Cervical spine osteochondroma in an 11-year-old boy with radicular symptoms. Radiographs (not shown) were normal. (a) Axial CT scan shows the narrow stalk and cortical continuity (arrowheads) at the spinolaminar junction of C5, pathognomonic of an osteochondroma. The lesion protrudes into the spinal canal. (b) Sagittal T1-weighted (500/25) MR image reveals fat signal intensity simulating a lipomatous lesion (arrows) resulting from the yellow marrow in the osteochondroma, but the continuity with bone is not seen. (c) Photograph of the sectioned gross specimen shows marrow space of the osteochondroma (*) and the thin hyaline cartilage cap (arrow).
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Figure 10b. Cervical spine osteochondroma in an 11-year-old boy with radicular symptoms. Radiographs (not shown) were normal. (a) Axial CT scan shows the narrow stalk and cortical continuity (arrowheads) at the spinolaminar junction of C5, pathognomonic of an osteochondroma. The lesion protrudes into the spinal canal. (b) Sagittal T1-weighted (500/25) MR image reveals fat signal intensity simulating a lipomatous lesion (arrows) resulting from the yellow marrow in the osteochondroma, but the continuity with bone is not seen. (c) Photograph of the sectioned gross specimen shows marrow space of the osteochondroma (*) and the thin hyaline cartilage cap (arrow).
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Figure 10c. Cervical spine osteochondroma in an 11-year-old boy with radicular symptoms. Radiographs (not shown) were normal. (a) Axial CT scan shows the narrow stalk and cortical continuity (arrowheads) at the spinolaminar junction of C5, pathognomonic of an osteochondroma. The lesion protrudes into the spinal canal. (b) Sagittal T1-weighted (500/25) MR image reveals fat signal intensity simulating a lipomatous lesion (arrows) resulting from the yellow marrow in the osteochondroma, but the continuity with bone is not seen. (c) Photograph of the sectioned gross specimen shows marrow space of the osteochondroma (*) and the thin hyaline cartilage cap (arrow).
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Figure 11a. Bursa formation overlying a scapular osteochondroma in a 20-year-old patient. (a-d) CT scans (bone [a] and soft-tissue [b] windows) and axial T1-weighted (640/20) (c) and T2-weighted (1,800/90) (d) MR images show a typical osteochondroma with continuity to the underlying scapula (arrow). However, the overlying component (*) is relatively thick and would be worrisome for malignant transformation if it represents a hyaline cartilage cap. (e) Intraoperative photograph shows tip of the osteochondroma (arrowhead) and overlying bursal sac (arrows) without a significant cartilage cap.
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Figure 11b. Bursa formation overlying a scapular osteochondroma in a 20-year-old patient. (a-d) CT scans (bone [a] and soft-tissue [b] windows) and axial T1-weighted (640/20) (c) and T2-weighted (1,800/90) (d) MR images show a typical osteochondroma with continuity to the underlying scapula (arrow). However, the overlying component (*) is relatively thick and would be worrisome for malignant transformation if it represents a hyaline cartilage cap. (e) Intraoperative photograph shows tip of the osteochondroma (arrowhead) and overlying bursal sac (arrows) without a significant cartilage cap.
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Figure 11c. Bursa formation overlying a scapular osteochondroma in a 20-year-old patient. (a-d) CT scans (bone [a] and soft-tissue [b] windows) and axial T1-weighted (640/20) (c) and T2-weighted (1,800/90) (d) MR images show a typical osteochondroma with continuity to the underlying scapula (arrow). However, the overlying component (*) is relatively thick and would be worrisome for malignant transformation if it represents a hyaline cartilage cap. (e) Intraoperative photograph shows tip of the osteochondroma (arrowhead) and overlying bursal sac (arrows) without a significant cartilage cap.
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Figure 11d. Bursa formation overlying a scapular osteochondroma in a 20-year-old patient. (a-d) CT scans (bone [a] and soft-tissue [b] windows) and axial T1-weighted (640/20) (c) and T2-weighted (1,800/90) (d) MR images show a typical osteochondroma with continuity to the underlying scapula (arrow). However, the overlying component (*) is relatively thick and would be worrisome for malignant transformation if it represents a hyaline cartilage cap. (e) Intraoperative photograph shows tip of the osteochondroma (arrowhead) and overlying bursal sac (arrows) without a significant cartilage cap.
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Figure 11e. Bursa formation overlying a scapular osteochondroma in a 20-year-old patient. (a-d) CT scans (bone [a] and soft-tissue [b] windows) and axial T1-weighted (640/20) (c) and T2-weighted (1,800/90) (d) MR images show a typical osteochondroma with continuity to the underlying scapula (arrow). However, the overlying component (*) is relatively thick and would be worrisome for malignant transformation if it represents a hyaline cartilage cap. (e) Intraoperative photograph shows tip of the osteochondroma (arrowhead) and overlying bursal sac (arrows) without a significant cartilage cap.
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Figure 12a. Hereditary multiple exostoses and an overlying bursa containing debris in a 42-year-old man with apparent rapid enlargement of a femoral osteochondroma. (a, b) Axial T2-weighted MR image (5,650/112) (a) and sonogram (b) show a fluid-filled mass (large arrowheads) with multiple filling defects (small arrowheads). (c) Photograph of the gross specimen shows that the mass corresponds to a bursa (large arrows) with multiple osteochondral fragments (small arrows) over a femoral osteochondroma rather than malignant transformation as was suspected clinically.
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Figure 12b. Hereditary multiple exostoses and an overlying bursa containing debris in a 42-year-old man with apparent rapid enlargement of a femoral osteochondroma. (a, b) Axial T2-weighted MR image (5,650/112) (a) and sonogram (b) show a fluid-filled mass (large arrowheads) with multiple filling defects (small arrowheads). (c) Photograph of the gross specimen shows that the mass corresponds to a bursa (large arrows) with multiple osteochondral fragments (small arrows) over a femoral osteochondroma rather than malignant transformation as was suspected clinically.
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Figure 12c. Hereditary multiple exostoses and an overlying bursa containing debris in a 42-year-old man with apparent rapid enlargement of a femoral osteochondroma. (a, b) Axial T2-weighted MR image (5,650/112) (a) and sonogram (b) show a fluid-filled mass (large arrowheads) with multiple filling defects (small arrowheads). (c) Photograph of the gross specimen shows that the mass corresponds to a bursa (large arrows) with multiple osteochondral fragments (small arrows) over a femoral osteochondroma rather than malignant transformation as was suspected clinically.
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Figure 13a. Solitary benign osteochondroma of the femur with small bursa and hyaline cartilage cap in a 13-year-old girl. Oblique coronal T2-weighted (2,500/80) (a) and fat-suppressed three-dimensional spoiled gradient-recalled (SPGR) (60/5; flip angle, 40°) (b) MR images show an osteochondroma with cortical and marrow continuity (arrowheads) to the underlying femur. The T2-weighted MR image (a) shows a thin band of high signal intensity at the lesion periphery (arrows) that could represent a cartilage cap or bursa. The SPGR MR image (b) allows distinction of these two possibilities with very thin high-signal-intensity cartilage cap caused by bound water (arrows) versus low-signal-intensity small bursa with free water (*). (Courtesy of David Disler, MD, St Mary's Hospital, Richmond, Va.)
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Figure 13b. Solitary benign osteochondroma of the femur with small bursa and hyaline cartilage cap in a 13-year-old girl. Oblique coronal T2-weighted (2,500/80) (a) and fat-suppressed three-dimensional spoiled gradient-recalled (SPGR) (60/5; flip angle, 40°) (b) MR images show an osteochondroma with cortical and marrow continuity (arrowheads) to the underlying femur. The T2-weighted MR image (a) shows a thin band of high signal intensity at the lesion periphery (arrows) that could represent a cartilage cap or bursa. The SPGR MR image (b) allows distinction of these two possibilities with very thin high-signal-intensity cartilage cap caused by bound water (arrows) versus low-signal-intensity small bursa with free water (*). (Courtesy of David Disler, MD, St Mary's Hospital, Richmond, Va.)
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Figure 14a. Malignant transformation to chondrosarcoma of a solitary fibular osteochondroma in a 35-year-old man who presented with a progressively enlarging mass. (a) Radiographs of the knee show an osteochondroma involving the tibia (large arrows) with an indistinct peripheral margin (small arrows) and scattered calcifications (arrowheads). (b) Photograph of a coronally sectioned whole-mount specimen (H-E stain) reveals the osteochondroma with cortical and marrow (arrowheads) continuity to the underlying tibia. The 4-cm-thick hyaline cartilage cap (*) with areas of calcification (arrows) represents low-grade chondrosarcoma from malignant transformation.
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Figure 14b. Malignant transformation to chondrosarcoma of a solitary fibular osteochondroma in a 35-year-old man who presented with a progressively enlarging mass. (a) Radiographs of the knee show an osteochondroma involving the tibia (large arrows) with an indistinct peripheral margin (small arrows) and scattered calcifications (arrowheads). (b) Photograph of a coronally sectioned whole-mount specimen (H-E stain) reveals the osteochondroma with cortical and marrow (arrowheads) continuity to the underlying tibia. The 4-cm-thick hyaline cartilage cap (*) with areas of calcification (arrows) represents low-grade chondrosarcoma from malignant transformation.
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Figure 15a. Malignant transformation to chondrosarcoma of an iliac osteochondroma in a 50-year-old man with HME. (a) Pelvic radiograph shows widened femoral metaphyses from tubulation abnormality associated with HME and calcification overlying and above the left iliac crest (arrows). (b-e) CT scan (b) and axial T1-weighted (500/16) (c), fat-suppressed gadolinium-enhanced T1-weighted (800/20) (d), and T2-weighted (3,216/68) (e) MR images show an osteochondroma of the left iliac crest with cortical and marrow continuity (arrows). There is a large associated overlying soft-issue mass (large arrowheads) containing multiple calcifications representing secondary chondrosarcoma arising from the cartilage cap. The high water content of this cartilaginous tissue is reflected in the low attenuation on the CT scan (b) and very high signal intensity on the T2-weighted MR image (e). Mild, predominantly peripheral and septal enhancement is seen after gadolinium administration (small arrowheads in d). (f, g) Photographs of coronally sectioned gross (f) and whole-mount (H-E stain) (g) specimens demonstrate the large soft-tissue component of the chondrosarcoma (arrows) adjacent to the iliac crest (*).
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Figure 15b. Malignant transformation to chondrosarcoma of an iliac osteochondroma in a 50-year-old man with HME. (a) Pelvic radiograph shows widened femoral metaphyses from tubulation abnormality associated with HME and calcification overlying and above the left iliac crest (arrows). (b-e) CT scan (b) and axial T1-weighted (500/16) (c), fat-suppressed gadolinium-enhanced T1-weighted (800/20) (d), and T2-weighted (3,216/68) (e) MR images show an osteochondroma of the left iliac crest with cortical and marrow continuity (arrows). There is a large associated overlying soft-issue mass (large arrowheads) containing multiple calcifications representing secondary chondrosarcoma arising from the cartilage cap. The high water content of this cartilaginous tissue is reflected in the low attenuation on the CT scan (b) and very high signal intensity on the T2-weighted MR image (e). Mild, predominantly peripheral and septal enhancement is seen after gadolinium administration (small arrowheads in d). (f, g) Photographs of coronally sectioned gross (f) and whole-mount (H-E stain) (g) specimens demonstrate the large soft-tissue component of the chondrosarcoma (arrows) adjacent to the iliac crest (*).
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Figure 15c. Malignant transformation to chondrosarcoma of an iliac osteochondroma in a 50-year-old man with HME. (a) Pelvic radiograph shows widened femoral metaphyses from tubulation abnormality associated with HME and calcification overlying and above the left iliac crest (arrows). (b-e) CT scan (b) and axial T1-weighted (500/16) (c), fat-suppressed gadolinium-enhanced T1-weighted (800/20) (d), and T2-weighted (3,216/68) (e) MR images show an osteochondroma of the left iliac crest with cortical and marrow continuity (arrows). There is a large associated overlying soft-issue mass (large arrowheads) containing multiple calcifications representing secondary chondrosarcoma arising from the cartilage cap. The high water content of this cartilaginous tissue is reflected in the low attenuation on the CT scan (b) and very high signal intensity on the T2-weighted MR image (e). Mild, predominantly peripheral and septal enhancement is seen after gadolinium administration (small arrowheads in d). (f, g) Photographs of coronally sectioned gross (f) and whole-mount (H-E stain) (g) specimens demonstrate the large soft-tissue component of the chondrosarcoma (arrows) adjacent to the iliac crest (*).
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Figure 15d. Malignant transformation to chondrosarcoma of an iliac osteochondroma in a 50-year-old man with HME. (a) Pelvic radiograph shows widened femoral metaphyses from tubulation abnormality associated with HME and calcification overlying and above the left iliac crest (arrows). (b-e) CT scan (b) and axial T1-weighted (500/16) (c), fat-suppressed gadolinium-enhanced T1-weighted (800/20) (d), and T2-weighted (3,216/68) (e) MR images show an osteochondroma of the left iliac crest with cortical and marrow continuity (arrows). There is a large associated overlying soft-issue mass (large arrowheads) containing multiple calcifications representing secondary chondrosarcoma arising from the cartilage cap. The high water content of this cartilaginous tissue is reflected in the low attenuation on the CT scan (b) and very high signal intensity on the T2-weighted MR image (e). Mild, predominantly peripheral and septal enhancement is seen after gadolinium administration (small arrowheads in d). (f, g) Photographs of coronally sectioned gross (f) and whole-mount (H-E stain) (g) specimens demonstrate the large soft-tissue component of the chondrosarcoma (arrows) adjacent to the iliac crest (*).
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Figure 15e. Malignant transformation to chondrosarcoma of an iliac osteochondroma in a 50-year-old man with HME. (a) Pelvic radiograph shows widened femoral metaphyses from tubulation abnormality associated with HME and calcification overlying and above the left iliac crest (arrows). (b-e) CT scan (b) and axial T1-weighted (500/16) (c), fat-suppressed gadolinium-enhanced T1-weighted (800/20) (d), and T2-weighted (3,216/68) (e) MR images show an osteochondroma of the left iliac crest with cortical and marrow continuity (arrows). There is a large associated overlying soft-issue mass (large arrowheads) containing multiple calcifications representing secondary chondrosarcoma arising from the cartilage cap. The high water content of this cartilaginous tissue is reflected in the low attenuation on the CT scan (b) and very high signal intensity on the T2-weighted MR image (e). Mild, predominantly peripheral and septal enhancement is seen after gadolinium administration (small arrowheads in d). (f, g) Photographs of coronally sectioned gross (f) and whole-mount (H-E stain) (g) specimens demonstrate the large soft-tissue component of the chondrosarcoma (arrows) adjacent to the iliac crest (*).
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Figure 15f. Malignant transformation to chondrosarcoma of an iliac osteochondroma in a 50-year-old man with HME. (a) Pelvic radiograph shows widened femoral metaphyses from tubulation abnormality associated with HME and calcification overlying and above the left iliac crest (arrows). (b-e) CT scan (b) and axial T1-weighted (500/16) (c), fat-suppressed gadolinium-enhanced T1-weighted (800/20) (d), and T2-weighted (3,216/68) (e) MR images show an osteochondroma of the left iliac crest with cortical and marrow continuity (arrows). There is a large associated overlying soft-issue mass (large arrowheads) containing multiple calcifications representing secondary chondrosarcoma arising from the cartilage cap. The high water content of this cartilaginous tissue is reflected in the low attenuation on the CT scan (b) and very high signal intensity on the T2-weighted MR image (e). Mild, predominantly peripheral and septal enhancement is seen after gadolinium administration (small arrowheads in d). (f, g) Photographs of coronally sectioned gross (f) and whole-mount (H-E stain) (g) specimens demonstrate the large soft-tissue component of the chondrosarcoma (arrows) adjacent to the iliac crest (*).
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Figure 15g. Malignant transformation to chondrosarcoma of an iliac osteochondroma in a 50-year-old man with HME. (a) Pelvic radiograph shows widened femoral metaphyses from tubulation abnormality associated with HME and calcification overlying and above the left iliac crest (arrows). (b-e) CT scan (b) and axial T1-weighted (500/16) (c), fat-suppressed gadolinium-enhanced T1-weighted (800/20) (d), and T2-weighted (3,216/68) (e) MR images show an osteochondroma of the left iliac crest with cortical and marrow continuity (arrows). There is a large associated overlying soft-issue mass (large arrowheads) containing multiple calcifications representing secondary chondrosarcoma arising from the cartilage cap. The high water content of this cartilaginous tissue is reflected in the low attenuation on the CT scan (b) and very high signal intensity on the T2-weighted MR image (e). Mild, predominantly peripheral and septal enhancement is seen after gadolinium administration (small arrowheads in d). (f, g) Photographs of coronally sectioned gross (f) and whole-mount (H-E stain) (g) specimens demonstrate the large soft-tissue component of the chondrosarcoma (arrows) adjacent to the iliac crest (*).
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