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From the Archives of the AFIP

Benign Musculoskeletal Lipomatous Lesions¹

¹ From the Departments of Radiologic Pathology (M.D.M., J.F.C., T.L.P.) and Orthopedic Pathology (F.H.G.), Armed Forces Institute of Pathology, 6825 16th St NW, Bldg 54, Rm M-133A, Washington, DC 20306; Department of Radiology, Medical University of South Carolina, Charleston (T.L.P.); Departments of Radiology and Nuclear Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md (M.D.M., D.J.F.); Department of Radiology, University of Maryland School of Medicine, Baltimore (M.D.M.); Department of Radiology, National Naval Medical Center, Bethesda, Md (D.J.F.); and Department of Radiology, Mayo Clinic, Jacksonville, Fla (M.J.K.). Received June 1, 2004; revision requested June 7 and received June 24; accepted June 24. All authors have no financial relationships to disclose. Address correspondence to M.D.M. (e-mail: murphey@afip.osd.mil).

View larger version (110K): [in a new window]   Figure 1a.  Subcutaneous lipoma superior to the clavicle in a 32-year-old woman. (a, b) Coronal T1-weighted (repetition time msec/echo time msec= 583/30) (a) and T2-weighted (2580/80) (b) MR images show a mass that is isointense relative to subcutaneous fat (*). It is surrounded by a low-signal-intensity capsule (arrows), which allows it to be distinguished from adjacent adipose tissue. (c) Photograph of the sectioned gross specimen reveals diffuse fat throughout the lesion (*) and the surrounding capsule (arrowheads).

View larger version (125K): [in a new window]   Figure 1b.  Subcutaneous lipoma superior to the clavicle in a 32-year-old woman. (a, b) Coronal T1-weighted (repetition time msec/echo time msec= 583/30) (a) and T2-weighted (2580/80) (b) MR images show a mass that is isointense relative to subcutaneous fat (*). It is surrounded by a low-signal-intensity capsule (arrows), which allows it to be distinguished from adjacent adipose tissue. (c) Photograph of the sectioned gross specimen reveals diffuse fat throughout the lesion (*) and the surrounding capsule (arrowheads).

View larger version (130K): [in a new window]   Figure 1c.  Subcutaneous lipoma superior to the clavicle in a 32-year-old woman. (a, b) Coronal T1-weighted (repetition time msec/echo time msec= 583/30) (a) and T2-weighted (2580/80) (b) MR images show a mass that is isointense relative to subcutaneous fat (*). It is surrounded by a low-signal-intensity capsule (arrows), which allows it to be distinguished from adjacent adipose tissue. (c) Photograph of the sectioned gross specimen reveals diffuse fat throughout the lesion (*) and the surrounding capsule (arrowheads).

View larger version (128K): [in a new window]   Figure 2a.  Deep infiltrating intramuscular lipoma of the calf in a 17-year-old boy with a palpable soft-tissue mass. (a) Axial T1-weighted (600/12) MR image shows a mass isointense relative to subcutaneous fat that infiltrates the soleus muscle (arrows) and extends across the intermuscular planes to more mildly involve other calf muscles (arrowheads). (b) Photograph of the axially sectioned gross specimen reveals infiltrating lipoma (black *) extensively interdigitating with the soleus muscle (white *).

View larger version (93K): [in a new window]   Figure 2b.  Deep infiltrating intramuscular lipoma of the calf in a 17-year-old boy with a palpable soft-tissue mass. (a) Axial T1-weighted (600/12) MR image shows a mass isointense relative to subcutaneous fat that infiltrates the soleus muscle (arrows) and extends across the intermuscular planes to more mildly involve other calf muscles (arrowheads). (b) Photograph of the axially sectioned gross specimen reveals infiltrating lipoma (black *) extensively interdigitating with the soleus muscle (white *).

View larger version (129K): [in a new window]   Figure 3a.  Deep intramuscular lipoma of the thigh in a 64-year-old woman with a slowly enlarging soft-tissue mass. (a) Radiograph of the proximal thigh shows a radiolucent soft-tissue mass (arrows). (b) CT scan reveals the low-attenuation lipomatous mass (*) with thin septa (arrowheads) in the anterior compartment of the thigh. (c, d) Axial T1-weighted (500/17) (c) and T2-weighted (2100/90) (d) MR images reveal a mass that is isointense relative to subcutaneous fat with both pulse sequences (*) and that contains thin delicate septa (arrows), which remain predominantly low signal intensity on the long TR image (d). (e) Photograph of the axially sectioned gross specimen demonstrates the lipomatous mass (*) with thin septa (arrowheads).

View larger version (81K): [in a new window]   Figure 3b.  Deep intramuscular lipoma of the thigh in a 64-year-old woman with a slowly enlarging soft-tissue mass. (a) Radiograph of the proximal thigh shows a radiolucent soft-tissue mass (arrows). (b) CT scan reveals the low-attenuation lipomatous mass (*) with thin septa (arrowheads) in the anterior compartment of the thigh. (c, d) Axial T1-weighted (500/17) (c) and T2-weighted (2100/90) (d) MR images reveal a mass that is isointense relative to subcutaneous fat with both pulse sequences (*) and that contains thin delicate septa (arrows), which remain predominantly low signal intensity on the long TR image (d). (e) Photograph of the axially sectioned gross specimen demonstrates the lipomatous mass (*) with thin septa (arrowheads).

View larger version (93K): [in a new window]   Figure 3c.  Deep intramuscular lipoma of the thigh in a 64-year-old woman with a slowly enlarging soft-tissue mass. (a) Radiograph of the proximal thigh shows a radiolucent soft-tissue mass (arrows). (b) CT scan reveals the low-attenuation lipomatous mass (*) with thin septa (arrowheads) in the anterior compartment of the thigh. (c, d) Axial T1-weighted (500/17) (c) and T2-weighted (2100/90) (d) MR images reveal a mass that is isointense relative to subcutaneous fat with both pulse sequences (*) and that contains thin delicate septa (arrows), which remain predominantly low signal intensity on the long TR image (d). (e) Photograph of the axially sectioned gross specimen demonstrates the lipomatous mass (*) with thin septa (arrowheads).

View larger version (78K): [in a new window]   Figure 3d.  Deep intramuscular lipoma of the thigh in a 64-year-old woman with a slowly enlarging soft-tissue mass. (a) Radiograph of the proximal thigh shows a radiolucent soft-tissue mass (arrows). (b) CT scan reveals the low-attenuation lipomatous mass (*) with thin septa (arrowheads) in the anterior compartment of the thigh. (c, d) Axial T1-weighted (500/17) (c) and T2-weighted (2100/90) (d) MR images reveal a mass that is isointense relative to subcutaneous fat with both pulse sequences (*) and that contains thin delicate septa (arrows), which remain predominantly low signal intensity on the long TR image (d). (e) Photograph of the axially sectioned gross specimen demonstrates the lipomatous mass (*) with thin septa (arrowheads).

View larger version (102K): [in a new window]   Figure 3e.  Deep intramuscular lipoma of the thigh in a 64-year-old woman with a slowly enlarging soft-tissue mass. (a) Radiograph of the proximal thigh shows a radiolucent soft-tissue mass (arrows). (b) CT scan reveals the low-attenuation lipomatous mass (*) with thin septa (arrowheads) in the anterior compartment of the thigh. (c, d) Axial T1-weighted (500/17) (c) and T2-weighted (2100/90) (d) MR images reveal a mass that is isointense relative to subcutaneous fat with both pulse sequences (*) and that contains thin delicate septa (arrows), which remain predominantly low signal intensity on the long TR image (d). (e) Photograph of the axially sectioned gross specimen demonstrates the lipomatous mass (*) with thin septa (arrowheads).

View larger version (149K): [in a new window]   Figure 4a.  Deep intramuscular lipoma with thick septa in a 60-year-old woman with a slowly enlarging mass in the thigh. (a, b) Coronal T1-weighted (600/30) (a) and T2-weighted (2000/90) (b) MR images show a heterogeneous mass (*) that is predominantly isointense relative to subcutaneous fat. However, prominent thick septations with some nodularity are also present (arrowheads), some of which reveal high signal intensity on the long TR image (b). These features do not allow distinction from well-differentiated liposarcoma. (c) Photograph of the longitudinally sectioned gross specimen demonstrates the lipomatous tissue (*) with thick septa and focal nodularity (arrows).

View larger version (143K): [in a new window]   Figure 4b.  Deep intramuscular lipoma with thick septa in a 60-year-old woman with a slowly enlarging mass in the thigh. (a, b) Coronal T1-weighted (600/30) (a) and T2-weighted (2000/90) (b) MR images show a heterogeneous mass (*) that is predominantly isointense relative to subcutaneous fat. However, prominent thick septations with some nodularity are also present (arrowheads), some of which reveal high signal intensity on the long TR image (b). These features do not allow distinction from well-differentiated liposarcoma. (c) Photograph of the longitudinally sectioned gross specimen demonstrates the lipomatous tissue (*) with thick septa and focal nodularity (arrows).

View larger version (95K): [in a new window]   Figure 4c.  Deep intramuscular lipoma with thick septa in a 60-year-old woman with a slowly enlarging mass in the thigh. (a, b) Coronal T1-weighted (600/30) (a) and T2-weighted (2000/90) (b) MR images show a heterogeneous mass (*) that is predominantly isointense relative to subcutaneous fat. However, prominent thick septations with some nodularity are also present (arrowheads), some of which reveal high signal intensity on the long TR image (b). These features do not allow distinction from well-differentiated liposarcoma. (c) Photograph of the longitudinally sectioned gross specimen demonstrates the lipomatous tissue (*) with thick septa and focal nodularity (arrows).

View larger version (127K): [in a new window]   Figure 5a.  Unencapsulated subcutaneous lipoma in a 40-year old man. (a) Axial T1-weighted MR image (545/16.5) shows a mass (*) with signal intensity identical to that of subcutaneous fat and that blends imperceptibly with surrounding adipose tissue. No low-signal-intensity capsule is seen separating the lipoma from the subcutaneous fat. Note the anterior marker in place for identifying this as the site of a palpable soft-tissue mass. (b) Photomicrograph (original magnification, x175; hematoxylin-eosin [H-E] stain) reveals typical large adipocytes that composed the entire lesion.

View larger version (111K): [in a new window]   Figure 5b.  Unencapsulated subcutaneous lipoma in a 40-year old man. (a) Axial T1-weighted MR image (545/16.5) shows a mass (*) with signal intensity identical to that of subcutaneous fat and that blends imperceptibly with surrounding adipose tissue. No low-signal-intensity capsule is seen separating the lipoma from the subcutaneous fat. Note the anterior marker in place for identifying this as the site of a palpable soft-tissue mass. (b) Photomicrograph (original magnification, x175; hematoxylin-eosin [H-E] stain) reveals typical large adipocytes that composed the entire lesion.

View larger version (140K): [in a new window]   Figure 6a.  Multiple symmetric lipomatosis in a 45-year-old man. (a) CT scan shows diffuse infiltration of fat between the lumbar paraspinal muscles (arrows), as well as infiltration of the left anterior abdominal wall musculature (*). (b) Photomicrograph (original magnification, x150; H-E stain) reveals lipomatous tissue (L) infiltrating muscle bundles (M).

View larger version (157K): [in a new window]   Figure 6b.  Multiple symmetric lipomatosis in a 45-year-old man. (a) CT scan shows diffuse infiltration of fat between the lumbar paraspinal muscles (arrows), as well as infiltration of the left anterior abdominal wall musculature (*). (b) Photomicrograph (original magnification, x150; H-E stain) reveals lipomatous tissue (L) infiltrating muscle bundles (M).

View larger version (101K): [in a new window]   Figure 7a.  Shoulder girdle lipomatosis in a 40-year-old man. (a) Clinical photograph shows diffuse infiltration and deformity of the shoulder and upper extremity. (b) CT scan reveals diffuse lipomatous infiltration largely affecting the subcutaneous tissues as the cause of the clinical disfigurement.

View larger version (132K): [in a new window]   Figure 7b.  Shoulder girdle lipomatosis in a 40-year-old man. (a) Clinical photograph shows diffuse infiltration and deformity of the shoulder and upper extremity. (b) CT scan reveals diffuse lipomatous infiltration largely affecting the subcutaneous tissues as the cause of the clinical disfigurement.

View larger version (135K): [in a new window]   Figure 8a.  Lipomatosis of the median nerve in a patient with macrodactyly. (a, b) Clinical photograph (a) and anteroposterior radiograph (b) show soft-tissue and bone overgrowth (arrow in b) of the second and third digits with osseous bowing. (c) Axial T1-weighted (500/20) MR image reveals diffuse overgrowth of fat in several digits (arrows). (d, e) Photographs of the sagittally sectioned gross specimen (d) and coronally sectioned whole-mount specimen (H-E stain) (e) of involved digits demonstrate osseous and soft-tissue hypertrophy with predominance of fat (*).

View larger version (119K): [in a new window]   Figure 8b.  Lipomatosis of the median nerve in a patient with macrodactyly. (a, b) Clinical photograph (a) and anteroposterior radiograph (b) show soft-tissue and bone overgrowth (arrow in b) of the second and third digits with osseous bowing. (c) Axial T1-weighted (500/20) MR image reveals diffuse overgrowth of fat in several digits (arrows). (d, e) Photographs of the sagittally sectioned gross specimen (d) and coronally sectioned whole-mount specimen (H-E stain) (e) of involved digits demonstrate osseous and soft-tissue hypertrophy with predominance of fat (*).

View larger version (85K): [in a new window]   Figure 8c.  Lipomatosis of the median nerve in a patient with macrodactyly. (a, b) Clinical photograph (a) and anteroposterior radiograph (b) show soft-tissue and bone overgrowth (arrow in b) of the second and third digits with osseous bowing. (c) Axial T1-weighted (500/20) MR image reveals diffuse overgrowth of fat in several digits (arrows). (d, e) Photographs of the sagittally sectioned gross specimen (d) and coronally sectioned whole-mount specimen (H-E stain) (e) of involved digits demonstrate osseous and soft-tissue hypertrophy with predominance of fat (*).

View larger version (127K): [in a new window]   Figure 8d.  Lipomatosis of the median nerve in a patient with macrodactyly. (a, b) Clinical photograph (a) and anteroposterior radiograph (b) show soft-tissue and bone overgrowth (arrow in b) of the second and third digits with osseous bowing. (c) Axial T1-weighted (500/20) MR image reveals diffuse overgrowth of fat in several digits (arrows). (d, e) Photographs of the sagittally sectioned gross specimen (d) and coronally sectioned whole-mount specimen (H-E stain) (e) of involved digits demonstrate osseous and soft-tissue hypertrophy with predominance of fat (*).

View larger version (97K): [in a new window]   Figure 8e.  Lipomatosis of the median nerve in a patient with macrodactyly. (a, b) Clinical photograph (a) and anteroposterior radiograph (b) show soft-tissue and bone overgrowth (arrow in b) of the second and third digits with osseous bowing. (c) Axial T1-weighted (500/20) MR image reveals diffuse overgrowth of fat in several digits (arrows). (d, e) Photographs of the sagittally sectioned gross specimen (d) and coronally sectioned whole-mount specimen (H-E stain) (e) of involved digits demonstrate osseous and soft-tissue hypertrophy with predominance of fat (*).

View larger version (95K): [in a new window]   Figure 9a.  Lipomatosis of the median nerve in a patient without macrodactyly. (a) Axial T1-weighted (783/15) MR image of the wrist shows marked thickening of the median nerve with adipose tissue surrounding the nerve fascicles (arrowheads). (b) Longitudinal sonogram of the wrist also reveals cablelike thickening of the median nerve fascicles (arrowheads) with intervening hyperechoic fat. (c) Intraoperative photograph of the wrist dissection demonstrates a diffusely thickened, yellow median nerve (arrow) resulting from the lipomatosis of the nerve. (d) Photomicrograph (original magnification, x200; H-E stain) shows diffuse lipomatous infiltration (L) of the surrounding nerve fascicles (N).

View larger version (136K): [in a new window]   Figure 9b.  Lipomatosis of the median nerve in a patient without macrodactyly. (a) Axial T1-weighted (783/15) MR image of the wrist shows marked thickening of the median nerve with adipose tissue surrounding the nerve fascicles (arrowheads). (b) Longitudinal sonogram of the wrist also reveals cablelike thickening of the median nerve fascicles (arrowheads) with intervening hyperechoic fat. (c) Intraoperative photograph of the wrist dissection demonstrates a diffusely thickened, yellow median nerve (arrow) resulting from the lipomatosis of the nerve. (d) Photomicrograph (original magnification, x200; H-E stain) shows diffuse lipomatous infiltration (L) of the surrounding nerve fascicles (N).

View larger version (104K): [in a new window]   Figure 9c.  Lipomatosis of the median nerve in a patient without macrodactyly. (a) Axial T1-weighted (783/15) MR image of the wrist shows marked thickening of the median nerve with adipose tissue surrounding the nerve fascicles (arrowheads). (b) Longitudinal sonogram of the wrist also reveals cablelike thickening of the median nerve fascicles (arrowheads) with intervening hyperechoic fat. (c) Intraoperative photograph of the wrist dissection demonstrates a diffusely thickened, yellow median nerve (arrow) resulting from the lipomatosis of the nerve. (d) Photomicrograph (original magnification, x200; H-E stain) shows diffuse lipomatous infiltration (L) of the surrounding nerve fascicles (N).

View larger version (129K): [in a new window]   Figure 9d.  Lipomatosis of the median nerve in a patient without macrodactyly. (a) Axial T1-weighted (783/15) MR image of the wrist shows marked thickening of the median nerve with adipose tissue surrounding the nerve fascicles (arrowheads). (b) Longitudinal sonogram of the wrist also reveals cablelike thickening of the median nerve fascicles (arrowheads) with intervening hyperechoic fat. (c) Intraoperative photograph of the wrist dissection demonstrates a diffusely thickened, yellow median nerve (arrow) resulting from the lipomatosis of the nerve. (d) Photomicrograph (original magnification, x200; H-E stain) shows diffuse lipomatous infiltration (L) of the surrounding nerve fascicles (N).

View larger version (161K): [in a new window]   Figure 10a.  Lipoblastoma in a 4-month-old boy with an anterior neck mass. (a) Axial contrast-enhanced CT scan shows a mass extending from the left side of the neck and deviating the trachea to the right. The periphery of the mass is composed of small foci of fat (arrowhead) separated by thin septa and areas of low attenuation representing myxoid tissue (curved arrow). A larger focus of soft-tissue attenuation (straight arrow) is present centrally. (b) Photograph of the axially sectioned gross specimen shows a solid central element (arrow). Note lack of the typical yellow color of fat in the surrounding lobules (*) secondary to an admixture of adipose and myxoid tissue in this lipoblastoma.

View larger version (122K): [in a new window]   Figure 10b.  Lipoblastoma in a 4-month-old boy with an anterior neck mass. (a) Axial contrast-enhanced CT scan shows a mass extending from the left side of the neck and deviating the trachea to the right. The periphery of the mass is composed of small foci of fat (arrowhead) separated by thin septa and areas of low attenuation representing myxoid tissue (curved arrow). A larger focus of soft-tissue attenuation (straight arrow) is present centrally. (b) Photograph of the axially sectioned gross specimen shows a solid central element (arrow). Note lack of the typical yellow color of fat in the surrounding lobules (*) secondary to an admixture of adipose and myxoid tissue in this lipoblastoma.

View larger version (78K): [in a new window]   Figure 11a.  Angiolipoma in the subcutaneous thigh of a 21-year-old man. (a, b) Coronal T1-weighted (500/14) (a) and axial proton-density fat-suppressed (2000/30) (b) MR images show a subcutaneous mass that is largely isointense relative to fat (arrows). Several small nodular foci are also seen that have a more serpentine appearance (arrowheads), suggestive of vessels on the fat-suppressed MR image (b). (c) Photomicrograph (original magnification, x150; H-E stain) reveals a lipomatous mass (L) with more cellular areas peripherally (arrows). The more cellular peripheral area, shown in a higher power insert (original magnification, x400; H-E stain), contains multiple fibrin microthrombi in small-caliber vessels (arrowheads).

View larger version (95K): [in a new window]   Figure 11b.  Angiolipoma in the subcutaneous thigh of a 21-year-old man. (a, b) Coronal T1-weighted (500/14) (a) and axial proton-density fat-suppressed (2000/30) (b) MR images show a subcutaneous mass that is largely isointense relative to fat (arrows). Several small nodular foci are also seen that have a more serpentine appearance (arrowheads), suggestive of vessels on the fat-suppressed MR image (b). (c) Photomicrograph (original magnification, x150; H-E stain) reveals a lipomatous mass (L) with more cellular areas peripherally (arrows). The more cellular peripheral area, shown in a higher power insert (original magnification, x400; H-E stain), contains multiple fibrin microthrombi in small-caliber vessels (arrowheads).

View larger version (135K): [in a new window]   Figure 11c.  Angiolipoma in the subcutaneous thigh of a 21-year-old man. (a, b) Coronal T1-weighted (500/14) (a) and axial proton-density fat-suppressed (2000/30) (b) MR images show a subcutaneous mass that is largely isointense relative to fat (arrows). Several small nodular foci are also seen that have a more serpentine appearance (arrowheads), suggestive of vessels on the fat-suppressed MR image (b). (c) Photomicrograph (original magnification, x150; H-E stain) reveals a lipomatous mass (L) with more cellular areas peripherally (arrows). The more cellular peripheral area, shown in a higher power insert (original magnification, x400; H-E stain), contains multiple fibrin microthrombi in small-caliber vessels (arrowheads).

View larger version (110K): [in a new window]   Figure 12a.  Chondroid lipoma in the shoulder of a 40 year-old-woman with scapular pain. (a) Anteroposterior radiograph shows chondro-osseous mineralization overlying the scapula (arrows). (b) Axial T1-weighted (500/17) MR image reveals lipomatous components peripherally (arrows) and low-attenuation chondroid areas centrally (*). T2-weighted MR image (not shown) revealed diffuse high signal intensity. (c) Photograph of the axially sectioned gross specimen shows a peripheral lipomatous component (arrows) with central lobules of chondroid tissue (*). (d) Photomicrograph (original magnification, x200; H-E stain) demonstrates adult fat cells (*) and lipoblasts (arrowheads) with intermixed chondroid tissue (C).

View larger version (141K): [in a new window]   Figure 12b.  Chondroid lipoma in the shoulder of a 40 year-old-woman with scapular pain. (a) Anteroposterior radiograph shows chondro-osseous mineralization overlying the scapula (arrows). (b) Axial T1-weighted (500/17) MR image reveals lipomatous components peripherally (arrows) and low-attenuation chondroid areas centrally (*). T2-weighted MR image (not shown) revealed diffuse high signal intensity. (c) Photograph of the axially sectioned gross specimen shows a peripheral lipomatous component (arrows) with central lobules of chondroid tissue (*). (d) Photomicrograph (original magnification, x200; H-E stain) demonstrates adult fat cells (*) and lipoblasts (arrowheads) with intermixed chondroid tissue (C).

View larger version (174K): [in a new window]   Figure 12c.  Chondroid lipoma in the shoulder of a 40 year-old-woman with scapular pain. (a) Anteroposterior radiograph shows chondro-osseous mineralization overlying the scapula (arrows). (b) Axial T1-weighted (500/17) MR image reveals lipomatous components peripherally (arrows) and low-attenuation chondroid areas centrally (*). T2-weighted MR image (not shown) revealed diffuse high signal intensity. (c) Photograph of the axially sectioned gross specimen shows a peripheral lipomatous component (arrows) with central lobules of chondroid tissue (*). (d) Photomicrograph (original magnification, x200; H-E stain) demonstrates adult fat cells (*) and lipoblasts (arrowheads) with intermixed chondroid tissue (C).

View larger version (168K): [in a new window]   Figure 12d.  Chondroid lipoma in the shoulder of a 40 year-old-woman with scapular pain. (a) Anteroposterior radiograph shows chondro-osseous mineralization overlying the scapula (arrows). (b) Axial T1-weighted (500/17) MR image reveals lipomatous components peripherally (arrows) and low-attenuation chondroid areas centrally (*). T2-weighted MR image (not shown) revealed diffuse high signal intensity. (c) Photograph of the axially sectioned gross specimen shows a peripheral lipomatous component (arrows) with central lobules of chondroid tissue (*). (d) Photomicrograph (original magnification, x200; H-E stain) demonstrates adult fat cells (*) and lipoblasts (arrowheads) with intermixed chondroid tissue (C).

View larger version (107K): [in a new window]   Figure 13a.  Spindle cell lipoma in the posterior neck in a 55-year-old man with a long history of a slowly growing mass. (a) Axial contrast-enhanced CT scan shows a complex heterogeneous soft-tissue mass with a small lipomatous component medially (arrowhead) and a markedly enhancing area laterally (*). (b) Photograph of the axially sectioned gross specimen reveals identical features with a yellow adipose component (F) and a red hemorrhagic area (H). (c) Photomicrograph (original magnification, x175; H-E stain) through the more vascular area demonstrates pseudoangiomatoid spaces (A), adult fat cells (arrows), and a single collagenized area (arrowheads).

View larger version (129K): [in a new window]   Figure 13b.  Spindle cell lipoma in the posterior neck in a 55-year-old man with a long history of a slowly growing mass. (a) Axial contrast-enhanced CT scan shows a complex heterogeneous soft-tissue mass with a small lipomatous component medially (arrowhead) and a markedly enhancing area laterally (*). (b) Photograph of the axially sectioned gross specimen reveals identical features with a yellow adipose component (F) and a red hemorrhagic area (H). (c) Photomicrograph (original magnification, x175; H-E stain) through the more vascular area demonstrates pseudoangiomatoid spaces (A), adult fat cells (arrows), and a single collagenized area (arrowheads).

View larger version (149K): [in a new window]   Figure 13c.  Spindle cell lipoma in the posterior neck in a 55-year-old man with a long history of a slowly growing mass. (a) Axial contrast-enhanced CT scan shows a complex heterogeneous soft-tissue mass with a small lipomatous component medially (arrowhead) and a markedly enhancing area laterally (*). (b) Photograph of the axially sectioned gross specimen reveals identical features with a yellow adipose component (F) and a red hemorrhagic area (H). (c) Photomicrograph (original magnification, x175; H-E stain) through the more vascular area demonstrates pseudoangiomatoid spaces (A), adult fat cells (arrows), and a single collagenized area (arrowheads).

View larger version (94K): [in a new window]   Figure 14a.  Hibernoma in a 27-year-old woman with a painless mass in the thigh. (a, b) Coronal T1-weighted (750/30) (a) and sagittal T2-weighted (2100/100) (b) MR images through the thigh show a mass with signal intensity similar to that of fat (arrows) with both sequences. Serpentine channels (arrowheads) are seen in the central portion of the lesion. (c) Anteroposterior image from angiography reveals intense diffuse staining of the mass. (d) Photograph of the axially sectioned gross specimen shows the typical yellow-brown color of hibernoma and central blood vessels (arrows). (e) Photomicrograph (original magnification, x200; H-E stain) of the specimen reveals typical granular eosinophilic cells (E) intermixed with univacuolar adult-type lipocytes (L).

View larger version (88K): [in a new window]   Figure 14b.  Hibernoma in a 27-year-old woman with a painless mass in the thigh. (a, b) Coronal T1-weighted (750/30) (a) and sagittal T2-weighted (2100/100) (b) MR images through the thigh show a mass with signal intensity similar to that of fat (arrows) with both sequences. Serpentine channels (arrowheads) are seen in the central portion of the lesion. (c) Anteroposterior image from angiography reveals intense diffuse staining of the mass. (d) Photograph of the axially sectioned gross specimen shows the typical yellow-brown color of hibernoma and central blood vessels (arrows). (e) Photomicrograph (original magnification, x200; H-E stain) of the specimen reveals typical granular eosinophilic cells (E) intermixed with univacuolar adult-type lipocytes (L).

View larger version (94K): [in a new window]   Figure 14c.  Hibernoma in a 27-year-old woman with a painless mass in the thigh. (a, b) Coronal T1-weighted (750/30) (a) and sagittal T2-weighted (2100/100) (b) MR images through the thigh show a mass with signal intensity similar to that of fat (arrows) with both sequences. Serpentine channels (arrowheads) are seen in the central portion of the lesion. (c) Anteroposterior image from angiography reveals intense diffuse staining of the mass. (d) Photograph of the axially sectioned gross specimen shows the typical yellow-brown color of hibernoma and central blood vessels (arrows). (e) Photomicrograph (original magnification, x200; H-E stain) of the specimen reveals typical granular eosinophilic cells (E) intermixed with univacuolar adult-type lipocytes (L).

View larger version (140K): [in a new window]   Figure 14d.  Hibernoma in a 27-year-old woman with a painless mass in the thigh. (a, b) Coronal T1-weighted (750/30) (a) and sagittal T2-weighted (2100/100) (b) MR images through the thigh show a mass with signal intensity similar to that of fat (arrows) with both sequences. Serpentine channels (arrowheads) are seen in the central portion of the lesion. (c) Anteroposterior image from angiography reveals intense diffuse staining of the mass. (d) Photograph of the axially sectioned gross specimen shows the typical yellow-brown color of hibernoma and central blood vessels (arrows). (e) Photomicrograph (original magnification, x200; H-E stain) of the specimen reveals typical granular eosinophilic cells (E) intermixed with univacuolar adult-type lipocytes (L).

View larger version (157K): [in a new window]   Figure 14e.  Hibernoma in a 27-year-old woman with a painless mass in the thigh. (a, b) Coronal T1-weighted (750/30) (a) and sagittal T2-weighted (2100/100) (b) MR images through the thigh show a mass with signal intensity similar to that of fat (arrows) with both sequences. Serpentine channels (arrowheads) are seen in the central portion of the lesion. (c) Anteroposterior image from angiography reveals intense diffuse staining of the mass. (d) Photograph of the axially sectioned gross specimen shows the typical yellow-brown color of hibernoma and central blood vessels (arrows). (e) Photomicrograph (original magnification, x200; H-E stain) of the specimen reveals typical granular eosinophilic cells (E) intermixed with univacuolar adult-type lipocytes (L).

View larger version (91K): [in a new window]   Figure 15a.  Incidentally discovered intraosseous lipoma in the calcaneus of a 42-year-old man. (a) Lateral radiograph of the calcaneus shows a radiolucent lesion with sclerotic margins (arrows). A central rim of sclerosis producing a bull’s-eye appearance (arrowheads) is also seen. (b) Axial CT scan through the calcaneus shows fat in the periphery of the lesion (*). Thin rim of ossification (arrows) surrounds a central area of fluid attenuation (C). (c, d) Coronal T1-weighted (500/30) (c) and coronal T2-weighted (2000/90) (d) MR images through the calcaneus reveal the lesion, which has an outer rim of adipose signal intensity (A) surrounding a central focus of fluid signal intensity (F). (e) Photomicrograph (original magnification, x125; H-E stain) shows central rim of ossification (O) at the margin of fat necrosis (FN) and surrounding viable fat in the intraosseous lipoma (L).

View larger version (90K): [in a new window]   Figure 15b.  Incidentally discovered intraosseous lipoma in the calcaneus of a 42-year-old man. (a) Lateral radiograph of the calcaneus shows a radiolucent lesion with sclerotic margins (arrows). A central rim of sclerosis producing a bull’s-eye appearance (arrowheads) is also seen. (b) Axial CT scan through the calcaneus shows fat in the periphery of the lesion (*). Thin rim of ossification (arrows) surrounds a central area of fluid attenuation (C). (c, d) Coronal T1-weighted (500/30) (c) and coronal T2-weighted (2000/90) (d) MR images through the calcaneus reveal the lesion, which has an outer rim of adipose signal intensity (A) surrounding a central focus of fluid signal intensity (F). (e) Photomicrograph (original magnification, x125; H-E stain) shows central rim of ossification (O) at the margin of fat necrosis (FN) and surrounding viable fat in the intraosseous lipoma (L).

View larger version (102K): [in a new window]   Figure 15c.  Incidentally discovered intraosseous lipoma in the calcaneus of a 42-year-old man. (a) Lateral radiograph of the calcaneus shows a radiolucent lesion with sclerotic margins (arrows). A central rim of sclerosis producing a bull’s-eye appearance (arrowheads) is also seen. (b) Axial CT scan through the calcaneus shows fat in the periphery of the lesion (*). Thin rim of ossification (arrows) surrounds a central area of fluid attenuation (C). (c, d) Coronal T1-weighted (500/30) (c) and coronal T2-weighted (2000/90) (d) MR images through the calcaneus reveal the lesion, which has an outer rim of adipose signal intensity (A) surrounding a central focus of fluid signal intensity (F). (e) Photomicrograph (original magnification, x125; H-E stain) shows central rim of ossification (O) at the margin of fat necrosis (FN) and surrounding viable fat in the intraosseous lipoma (L).

View larger version (81K): [in a new window]   Figure 15d.  Incidentally discovered intraosseous lipoma in the calcaneus of a 42-year-old man. (a) Lateral radiograph of the calcaneus shows a radiolucent lesion with sclerotic margins (arrows). A central rim of sclerosis producing a bull’s-eye appearance (arrowheads) is also seen. (b) Axial CT scan through the calcaneus shows fat in the periphery of the lesion (*). Thin rim of ossification (arrows) surrounds a central area of fluid attenuation (C). (c, d) Coronal T1-weighted (500/30) (c) and coronal T2-weighted (2000/90) (d) MR images through the calcaneus reveal the lesion, which has an outer rim of adipose signal intensity (A) surrounding a central focus of fluid signal intensity (F). (e) Photomicrograph (original magnification, x125; H-E stain) shows central rim of ossification (O) at the margin of fat necrosis (FN) and surrounding viable fat in the intraosseous lipoma (L).

View larger version (120K): [in a new window]   Figure 15e.  Incidentally discovered intraosseous lipoma in the calcaneus of a 42-year-old man. (a) Lateral radiograph of the calcaneus shows a radiolucent lesion with sclerotic margins (arrows). A central rim of sclerosis producing a bull’s-eye appearance (arrowheads) is also seen. (b) Axial CT scan through the calcaneus shows fat in the periphery of the lesion (*). Thin rim of ossification (arrows) surrounds a central area of fluid attenuation (C). (c, d) Coronal T1-weighted (500/30) (c) and coronal T2-weighted (2000/90) (d) MR images through the calcaneus reveal the lesion, which has an outer rim of adipose signal intensity (A) surrounding a central focus of fluid signal intensity (F). (e) Photomicrograph (original magnification, x125; H-E stain) shows central rim of ossification (O) at the margin of fat necrosis (FN) and surrounding viable fat in the intraosseous lipoma (L).

View larger version (112K): [in a new window]   Figure 16a.  Intraosseous lipoma discovered incidentally at intravenous urography in a 71-year-old man. (a) Anteroposterior radiograph of the pelvis shows a radiolucent lesion with a sclerotic rim (arrows) in the right ilium, adjacent to the sacroiliac joint. (b) Axial CT scan reveals fat attenuation in the anterior portion of the lesion (arrowheads) and fluid attenuation (arrows) posteriorly. (c) Follow-up CT scan obtained 6 months later shows that the lesion is now entirely low attenuation and fluid filled.

View larger version (106K): [in a new window]   Figure 16b.  Intraosseous lipoma discovered incidentally at intravenous urography in a 71-year-old man. (a) Anteroposterior radiograph of the pelvis shows a radiolucent lesion with a sclerotic rim (arrows) in the right ilium, adjacent to the sacroiliac joint. (b) Axial CT scan reveals fat attenuation in the anterior portion of the lesion (arrowheads) and fluid attenuation (arrows) posteriorly. (c) Follow-up CT scan obtained 6 months later shows that the lesion is now entirely low attenuation and fluid filled.

View larger version (110K): [in a new window]   Figure 16c.  Intraosseous lipoma discovered incidentally at intravenous urography in a 71-year-old man. (a) Anteroposterior radiograph of the pelvis shows a radiolucent lesion with a sclerotic rim (arrows) in the right ilium, adjacent to the sacroiliac joint. (b) Axial CT scan reveals fat attenuation in the anterior portion of the lesion (arrowheads) and fluid attenuation (arrows) posteriorly. (c) Follow-up CT scan obtained 6 months later shows that the lesion is now entirely low attenuation and fluid filled.

View larger version (107K): [in a new window]   Figure 17a.  Incidentally discovered intraosseous lipoma of the fibula in a 34-year-old woman. (a) Anteroposterior radiograph of the knee shows an expansile nonaggressive lesion in the proximal fibular diaphysis that contains central mineralization suggestive of chondroid matrix (arrows). (b) Coronal T1-weighted (460/20) MR image of the lower leg shows the fibular lesion, which has centrally increased signal intensity, similar to that of fat (*). (c) Photograph of the sagittally sectioned whole-mount specimen (H-E stain) reveals ischemic ossification (*), responsible for opacity in the lesion at radiography, and surrounding lipoma (L).

View larger version (117K): [in a new window]   Figure 17b.  Incidentally discovered intraosseous lipoma of the fibula in a 34-year-old woman. (a) Anteroposterior radiograph of the knee shows an expansile nonaggressive lesion in the proximal fibular diaphysis that contains central mineralization suggestive of chondroid matrix (arrows). (b) Coronal T1-weighted (460/20) MR image of the lower leg shows the fibular lesion, which has centrally increased signal intensity, similar to that of fat (*). (c) Photograph of the sagittally sectioned whole-mount specimen (H-E stain) reveals ischemic ossification (*), responsible for opacity in the lesion at radiography, and surrounding lipoma (L).

View larger version (57K): [in a new window]   Figure 17c.  Incidentally discovered intraosseous lipoma of the fibula in a 34-year-old woman. (a) Anteroposterior radiograph of the knee shows an expansile nonaggressive lesion in the proximal fibular diaphysis that contains central mineralization suggestive of chondroid matrix (arrows). (b) Coronal T1-weighted (460/20) MR image of the lower leg shows the fibular lesion, which has centrally increased signal intensity, similar to that of fat (*). (c) Photograph of the sagittally sectioned whole-mount specimen (H-E stain) reveals ischemic ossification (*), responsible for opacity in the lesion at radiography, and surrounding lipoma (L).

View larger version (86K): [in a new window]   Figure 18a.  Parosteal lipoma in a 47-year-old woman with a slowly enlarging, painless mass in the anteromedial upper arm. (a) Radiograph shows ossification (arrows) with surrounding radiolucency that represents fat (F) projecting over the proximal humeral diaphysis. (b) Axial CT scan shows fat attenuation (F) surrounding the irregular ossification arising from the anteromedial aspect of the proximal humerus (O). No medullary continuity is seen between underlying bone and surface bone formation. Bone scan (not shown) revealed moderate radionuclide uptake in this region. (c) Sagittal T1-weighted (500/30) MR image shows hyperintense signal of fat in the lesion (F) and low signal intensity in the surface bone formation (arrow). (d, e) Photograph of the sagittally sectioned gross specimen (d) and sagittally sectioned whole-mount specimen (H-E stain) (e) reveals central ossification (O) attached to the humeral cortex (C) without marrow continuity and surrounded by yellow adipose tissue (A). Humeral marrow (M) is normal.

View larger version (113K): [in a new window]   Figure 18b.  Parosteal lipoma in a 47-year-old woman with a slowly enlarging, painless mass in the anteromedial upper arm. (a) Radiograph shows ossification (arrows) with surrounding radiolucency that represents fat (F) projecting over the proximal humeral diaphysis. (b) Axial CT scan shows fat attenuation (F) surrounding the irregular ossification arising from the anteromedial aspect of the proximal humerus (O). No medullary continuity is seen between underlying bone and surface bone formation. Bone scan (not shown) revealed moderate radionuclide uptake in this region. (c) Sagittal T1-weighted (500/30) MR image shows hyperintense signal of fat in the lesion (F) and low signal intensity in the surface bone formation (arrow). (d, e) Photograph of the sagittally sectioned gross specimen (d) and sagittally sectioned whole-mount specimen (H-E stain) (e) reveals central ossification (O) attached to the humeral cortex (C) without marrow continuity and surrounded by yellow adipose tissue (A). Humeral marrow (M) is normal.

View larger version (109K): [in a new window]   Figure 18c.  Parosteal lipoma in a 47-year-old woman with a slowly enlarging, painless mass in the anteromedial upper arm. (a) Radiograph shows ossification (arrows) with surrounding radiolucency that represents fat (F) projecting over the proximal humeral diaphysis. (b) Axial CT scan shows fat attenuation (F) surrounding the irregular ossification arising from the anteromedial aspect of the proximal humerus (O). No medullary continuity is seen between underlying bone and surface bone formation. Bone scan (not shown) revealed moderate radionuclide uptake in this region. (c) Sagittal T1-weighted (500/30) MR image shows hyperintense signal of fat in the lesion (F) and low signal intensity in the surface bone formation (arrow). (d, e) Photograph of the sagittally sectioned gross specimen (d) and sagittally sectioned whole-mount specimen (H-E stain) (e) reveals central ossification (O) attached to the humeral cortex (C) without marrow continuity and surrounded by yellow adipose tissue (A). Humeral marrow (M) is normal.

View larger version (154K): [in a new window]   Figure 18d.  Parosteal lipoma in a 47-year-old woman with a slowly enlarging, painless mass in the anteromedial upper arm. (a) Radiograph shows ossification (arrows) with surrounding radiolucency that represents fat (F) projecting over the proximal humeral diaphysis. (b) Axial CT scan shows fat attenuation (F) surrounding the irregular ossification arising from the anteromedial aspect of the proximal humerus (O). No medullary continuity is seen between underlying bone and surface bone formation. Bone scan (not shown) revealed moderate radionuclide uptake in this region. (c) Sagittal T1-weighted (500/30) MR image shows hyperintense signal of fat in the lesion (F) and low signal intensity in the surface bone formation (arrow). (d, e) Photograph of the sagittally sectioned gross specimen (d) and sagittally sectioned whole-mount specimen (H-E stain) (e) reveals central ossification (O) attached to the humeral cortex (C) without marrow continuity and surrounded by yellow adipose tissue (A). Humeral marrow (M) is normal.

View larger version (129K): [in a new window]   Figure 18e.  Parosteal lipoma in a 47-year-old woman with a slowly enlarging, painless mass in the anteromedial upper arm. (a) Radiograph shows ossification (arrows) with surrounding radiolucency that represents fat (F) projecting over the proximal humeral diaphysis. (b) Axial CT scan shows fat attenuation (F) surrounding the irregular ossification arising from the anteromedial aspect of the proximal humerus (O). No medullary continuity is seen between underlying bone and surface bone formation. Bone scan (not shown) revealed moderate radionuclide uptake in this region. (c) Sagittal T1-weighted (500/30) MR image shows hyperintense signal of fat in the lesion (F) and low signal intensity in the surface bone formation (arrow). (d, e) Photograph of the sagittally sectioned gross specimen (d) and sagittally sectioned whole-mount specimen (H-E stain) (e) reveals central ossification (O) attached to the humeral cortex (C) without marrow continuity and surrounded by yellow adipose tissue (A). Humeral marrow (M) is normal.

View larger version (106K): [in a new window]   Figure 19a.  Liposclerosing myxofibrous tumor of the intertrochanteric femur in a 39-year-old man with mild hip pain. (a) Anteroposterior radiograph of the left hip shows a geographic lytic lesion involving the femur with a thin well-defined sclerotic margin (arrows) and containing globular amorphous mineralized matrix (*). (b) Coronal T1-weighted (700/33) MR image demonstrates the lesion (arrows), which has signal intensity similar to that of skeletal muscle. (c) Coronal T2-weighted (2000/100) MR image shows the moderately heterogeneous and predominantly high-signal-intensity tumor (arrows) with a well-defined margin. (d) Technetium 99m methylene diphosphonate bone scan of the pelvis shows mild focal increased radionuclide uptake in the lesion (arrowheads). (e) Photomicrograph (original magnification, x175; H-E stain) shows an area of prominent fibroxanthomatous and myxoid tissue (amorphous pink areas) intermixed with a small area of focal adipocytes (A).

View larger version (120K): [in a new window]   Figure 19b.  Liposclerosing myxofibrous tumor of the intertrochanteric femur in a 39-year-old man with mild hip pain. (a) Anteroposterior radiograph of the left hip shows a geographic lytic lesion involving the femur with a thin well-defined sclerotic margin (arrows) and containing globular amorphous mineralized matrix (*). (b) Coronal T1-weighted (700/33) MR image demonstrates the lesion (arrows), which has signal intensity similar to that of skeletal muscle. (c) Coronal T2-weighted (2000/100) MR image shows the moderately heterogeneous and predominantly high-signal-intensity tumor (arrows) with a well-defined margin. (d) Technetium 99m methylene diphosphonate bone scan of the pelvis shows mild focal increased radionuclide uptake in the lesion (arrowheads). (e) Photomicrograph (original magnification, x175; H-E stain) shows an area of prominent fibroxanthomatous and myxoid tissue (amorphous pink areas) intermixed with a small area of focal adipocytes (A).

View larger version (96K): [in a new window]   Figure 19c.  Liposclerosing myxofibrous tumor of the intertrochanteric femur in a 39-year-old man with mild hip pain. (a) Anteroposterior radiograph of the left hip shows a geographic lytic lesion involving the femur with a thin well-defined sclerotic margin (arrows) and containing globular amorphous mineralized matrix (*). (b) Coronal T1-weighted (700/33) MR image demonstrates the lesion (arrows), which has signal intensity similar to that of skeletal muscle. (c) Coronal T2-weighted (2000/100) MR image shows the moderately heterogeneous and predominantly high-signal-intensity tumor (arrows) with a well-defined margin. (d) Technetium 99m methylene diphosphonate bone scan of the pelvis shows mild focal increased radionuclide uptake in the lesion (arrowheads). (e) Photomicrograph (original magnification, x175; H-E stain) shows an area of prominent fibroxanthomatous and myxoid tissue (amorphous pink areas) intermixed with a small area of focal adipocytes (A).