DOI: 10.1148/rg.271065065
RadioGraphics 2007;27:173-187
Pathologic and MR Imaging Features of Benign Fibrous Soft-Tissue Tumors in Adults1
Philip A. Dinauer, MD,
Clark J. Brixey, MD,
Joel T. Moncur, MD,
Julie C. Fanburg-Smith, MD and
Mark D. Murphey, MD
1 From the Department of Diagnostic Radiology, Hospital of Saint Raphael, 1450 Chapel St, New Haven, CT 06511 (P.A.D.); Departments of Radiology (C.J.B., M.D.M.) and Pathology (J.T.M.), Walter Reed Army Medical Center, Washington, DC; Departments of Radiologic Pathology (M.D.M.) and Soft Tissue Pathology (J.C.F.), Armed Forces Institute of Pathology, Washington, DC; and Departments of Radiology and Nuclear Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md (P.A.D., M.D.M.). Presented as an education exhibit at the 2005 RSNA Annual Meeting. Received April 17, 2006; revision requested May 1 and received June 7; accepted June 15. All authors have no financial relationships to disclose.
Address correspondence to P.A.D. (e-mail: padinauer{at}yahoo.com).
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Abstract
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Benign fibrous (fibroblastic or myofibroblastic) soft-tissue tumors are a heterogeneous group of fibrous lesions with widely varied anatomic locations, biologic behavior, and pathologic features. The four broad categories of fibrous proliferation are benign fibrous proliferations, fibromatoses, fibrosarcomas, and fibrous proliferations of infancy and childhood. The first two categories include nonaggressive fibroblastic lesions such as nodular fasciitis, as well as fibromatoses that demonstrate more aggressive biologic behavior (eg, desmoid tumors). In adults, fibrous tumors are among the most common soft-tissue lesions encountered in clinical practice. MR imaging can be useful for defining the intrinsic signal characteristics, size, and compartmental extension of these lesions. Histologic features of the tumor also may be depicted on T2-weighted MR images. Hypocellular fibrous tumors with dense collagenous components tend to have lower signal intensity on T2-weighted images than do lesions that are more cellular or that contain greater amounts of extracellular myxoid matrix. When interpreting MR images of soft-tissue masses in adults, radiologists should be aware of the clinical behavior, common sites of occurrence, and histopathologic and imaging features of the common benign fibrous soft-tissue tumors.
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:- Recognize MR imaging characteristics that represent typical histopathologic features of benign fibrous soft-tissue tumors.
- Describe typical anatomic locations of benign fibrous proliferations such as nodular fasciitis and fibromatoses.
- Identify treatment options and assess recurrence risks for benign fibrous proliferations and extraabdominal desmoid tumors.
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Introduction
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Although benign fibrous (fibroblastic, myofibroblastic) soft-tissue tumors vary widely in their biologic behavior, pathologic features, and most common anatomic locations, they can be grouped in the following four broad categories: benign fibrous proliferations, fibromatoses, fibrosarcomas, and fibrous proliferations of infancy and childhood (1). This article is focused on the first two categories, which include nonaggressive fibroblastic lesions such as nodular fasciitis as well as fibromatoses that tend to demonstrate more aggressive, infiltrative growth (eg, desmoid tumors) (Table). In adults, benign fibrous tumors are among the most commonly encountered soft-tissue lesions in clinical practice. In a review of 18,677 benign soft-tissue tumors seen during pathologic consultation over a 10-year period at the Armed Forces Institute of Pathology, nodular fasciitis and fibromatosis were the third and fifth most common lesions, respectively (2).
Benign fibroblastic proliferations include entities such as nodular fasciitis and proliferative fasciitis, which usually are manifested as small (<4 cm) superficial masses. These highly cellular lesions initially tend to grow rapidly and clinically simulate malignant neoplasms. However, they have a self-limited course, rarely recur after excision, and never metastasize (1,3). Other distinct fibroblastic proliferations, such as elastofibromas, fibromas of the tendon sheath, and keloids, are more collagenous and less cellular than is nodular fasciitis. Fibromatoses, which may be broadly divided into superficial and deep forms, typically show more aggressive biologic behavior than do benign fibrous proliferations. Lesions in deep anatomic locations tend to grow more rapidly, reach a larger size (>5 cm), and more frequently recur locally after surgical excision than do superficial lesions.
MR imaging allows accurate assessment of the size and extent of fibrous lesions before biopsy or excision. In addition, MR imaging may be useful for following the treatment response, especially in infiltrative tumors that involve major neurovascular structures and that are treated with adjuvant radiation or chemotherapy. Furthermore, potentially useful histologic information may be represented on T2-weighted images. Hypocellular fibrous tumors with dense collagenous components tend to show lower signal intensity on T2-weighted images than do lesions that are more cellular or that have greater amounts of extracellular myxoid matrix (4–6). For some fibrous tumors, such as plantar fibromatosis and desmoid tumor, the histologic information that is represented on MR images may influence planning for the timing of surgical treatment. Lesions that are predominantly cellular may be associated with a higher risk of recurrence at the surgical site than are hypocellular, densely collagenous lesions (7). When interpreting MR images of soft-tissue masses in adults, radiologists should be aware of the clinical behavior, common sites of manifestation, and histopathologic and imaging features of the relatively common group of benign fibrous soft-tissue tumors.
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Benign Fibroblastic Proliferations
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Nodular Fasciitis
Nodular fasciitis is a benign proliferation of fibro-blasts and myofibroblasts that may be mistaken for a sarcomatous lesion because of its rapid growth, abundant spindle-shaped cells, and mitotic activity (1). Nodular fasciitis is probably the most common benign mesenchymal lesion that is histopathologically misdiagnosed as sarcoma, with resultant unnecessary or overly aggressive surgical therapy (1). The pathogenesis of nodular fasciitis is poorly understood. Some investigators have described it as a reactive lesion that may originate from trauma, whereas others have described chromosomal abnormalities that are suggestive of a neoplastic origin (8).
Nodular fasciitis most often occurs in patients between 20 and 40 years of age, although children also may be affected. It is typically manifested as a rapidly growing mass. In 46% of cases, it is localized to the upper extremity, particularly the volar aspect of the forearm (Figs 1, 2) (1,9, 10). Other sites of manifestation are the trunk (20%), head and neck (18%), and lower extremities (16%) (1,9,10). Symptoms of tenderness and pain are frequently described at presentation (10). The lesions tend to be small (<4 cm), and most (71%) have a maximal diameter of less than 2 cm (11). Three general subtypes of nodular fasciitis may be identified on the basis of the lesion location (subcutaneous, intramuscular, or fascial) (1,12,13). Dermal and intravascular lesions are rare. Most occurrences of nodular fasciitis are subcutaneous, fascia based, and circumscribed; these lesions may be amenable to biopsy or excision without any need for imaging evaluation. Lesions of the intramuscular subtype, because of their larger size, deeper location, and less defined borders, may mimic soft-tissue malignancies both at clinical evaluation and at imaging (3).
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Figure 1a. Subcutaneous fascia-based nodular fasciitis in the upper arm of a 38-year-old man. (a) Axial T1-weighted image shows a small nodule (arrow) localized to fascia on the lateral surface of the brachialis muscle. The lesion dimensions were 0.8 x 0.3 x 1.1 cm. (b) Photomicrograph (hematoxylineosin [H-E] stain) at low power demonstrates a well-circumscribed myxoid and spindle cell lesion (*) in fascia, centered between subcutaneous fat (A) and skeletal muscle (M).
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Figure 1b. Subcutaneous fascia-based nodular fasciitis in the upper arm of a 38-year-old man. (a) Axial T1-weighted image shows a small nodule (arrow) localized to fascia on the lateral surface of the brachialis muscle. The lesion dimensions were 0.8 x 0.3 x 1.1 cm. (b) Photomicrograph (hematoxylineosin [H-E] stain) at low power demonstrates a well-circumscribed myxoid and spindle cell lesion (*) in fascia, centered between subcutaneous fat (A) and skeletal muscle (M).
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Figure 2a. Fascia-based nodular fasciitis in the forearm of a 34-year-old woman with a clinical history of a palpable, rapidly enlarging mass. (a) Axial T1-weighted image shows a 3-cm mass (arrow) in the fascia along the radial aspect of the forearm. (b) Coronal short inversion time inversion recovery image shows linear extension of the lesion (arrows) superficially along the fascia. Although the lesion has nonspecific high signal intensity, nodular fasciitis should be the primary diagnostic consideration because of the lesion’s small size and forearm location and the patient’s age and clinical history.
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Figure 2b. Fascia-based nodular fasciitis in the forearm of a 34-year-old woman with a clinical history of a palpable, rapidly enlarging mass. (a) Axial T1-weighted image shows a 3-cm mass (arrow) in the fascia along the radial aspect of the forearm. (b) Coronal short inversion time inversion recovery image shows linear extension of the lesion (arrows) superficially along the fascia. Although the lesion has nonspecific high signal intensity, nodular fasciitis should be the primary diagnostic consideration because of the lesion’s small size and forearm location and the patient’s age and clinical history.
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Nodular fasciitis may be categorized as myxoid, cellular, or fibrous, according to the predominant histologic feature of the lesion (10,12). A relationship between the age of the lesion and the histologic subtype has been suggested, with early-stage lesions containing more cellular or myxoid components and with more mature lesions containing more fibrous components (3,10,14). However, a consistent association between lesion age and pathologic subtype has not been demonstrated (15). The histologic diversity of nodular fasciitis likely accounts for the variable MR imaging appearance of the lesions. The signal in hypercellular lesions appears nearly isointense to that in skeletal muscle on T1-weighted images and hyperintense to that in adipose tissue on T2-weighted images (Fig 3) (4). Highly collagenous lesions have hypointense signal on all MR images. Contrast enhancement is typically diffuse but may be peripheral in lesions with a greater extra-cellular myxoid matrix and central fluid-filled spaces (Fig 4) (12,16). The differential diagnosis at MR imaging includes extraabdominal desmoid tumor, neurofibroma, fibrous histiocytoma, and soft-tissue sarcoma. In the presence of an intramuscular lesion, early myositis ossificans may be considered in the differential diagnosis, as well. The imaging-based diagnosis should be verified with an excisional biopsy. Successful treatment typically consists of marginal excision alone, after which there is a 1% incidence of recurrence (17). However, given the self-limited course of nodular fasciitis, several weeks of observation (after a diagnosis based on the results of percutaneous fine-needle biopsy) also have been advocated (18,19). Spontaneous regression and involution of lesions in response to steroid injections have been reported (20).
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Figure 3a. Fascia-based nodular fasciitis in the proximal forearm of a 44-year-old man. (a) Axial T1-weighted image shows a well-defined 1.1 x 1.4-cm mass (arrow) with signal that is nearly isointense to that of skeletal muscle. The mass is centered on the bicipital aponeurosis and overlies the pronator teres muscle. (b) Axial T2-weighted fat-suppressed fast SE image shows homogeneous high signal intensity in the lesion (arrow). (c) Coronal T1-weighted fat-suppressed image shows diffuse enhancement of the lesion (arrow). (d) Photomicrograph (H-E stain) at intermediate power shows alternating cellularity and foci of myxoid degeneration (M), classic features of nodular fasciitis.
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Figure 3b. Fascia-based nodular fasciitis in the proximal forearm of a 44-year-old man. (a) Axial T1-weighted image shows a well-defined 1.1 x 1.4-cm mass (arrow) with signal that is nearly isointense to that of skeletal muscle. The mass is centered on the bicipital aponeurosis and overlies the pronator teres muscle. (b) Axial T2-weighted fat-suppressed fast SE image shows homogeneous high signal intensity in the lesion (arrow). (c) Coronal T1-weighted fat-suppressed image shows diffuse enhancement of the lesion (arrow). (d) Photomicrograph (H-E stain) at intermediate power shows alternating cellularity and foci of myxoid degeneration (M), classic features of nodular fasciitis.
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Figure 3c. Fascia-based nodular fasciitis in the proximal forearm of a 44-year-old man. (a) Axial T1-weighted image shows a well-defined 1.1 x 1.4-cm mass (arrow) with signal that is nearly isointense to that of skeletal muscle. The mass is centered on the bicipital aponeurosis and overlies the pronator teres muscle. (b) Axial T2-weighted fat-suppressed fast SE image shows homogeneous high signal intensity in the lesion (arrow). (c) Coronal T1-weighted fat-suppressed image shows diffuse enhancement of the lesion (arrow). (d) Photomicrograph (H-E stain) at intermediate power shows alternating cellularity and foci of myxoid degeneration (M), classic features of nodular fasciitis.
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Figure 3d. Fascia-based nodular fasciitis in the proximal forearm of a 44-year-old man. (a) Axial T1-weighted image shows a well-defined 1.1 x 1.4-cm mass (arrow) with signal that is nearly isointense to that of skeletal muscle. The mass is centered on the bicipital aponeurosis and overlies the pronator teres muscle. (b) Axial T2-weighted fat-suppressed fast SE image shows homogeneous high signal intensity in the lesion (arrow). (c) Coronal T1-weighted fat-suppressed image shows diffuse enhancement of the lesion (arrow). (d) Photomicrograph (H-E stain) at intermediate power shows alternating cellularity and foci of myxoid degeneration (M), classic features of nodular fasciitis.
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Figure 4a. Painful intramuscular nodular fasciitis in the upper arm of a 46-year-old woman. (a) Axial T2-weighted image shows a 3 x 3.5-cm hyperintense mass in the medial triceps. The mass has lower signal intensity along its periphery (arrow). (b) Coronal gadolinium-enhanced T1-weighted image shows peripheral enhancement of the lesion, with no appreciable enhancement in the predominantly myxoid center. (c) The nodule was exposed and removed with marginal excision after surgical dissection through the long head of the triceps. (d) Photomicrograph (H-E stain) shows fascia (lower left) with typical myxoid degeneration (M) predominantly in the central portion of the lesion. Note the peripheral parallel vessels at the interface between the fascia and the lesion.
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Figure 4b. Painful intramuscular nodular fasciitis in the upper arm of a 46-year-old woman. (a) Axial T2-weighted image shows a 3 x 3.5-cm hyperintense mass in the medial triceps. The mass has lower signal intensity along its periphery (arrow). (b) Coronal gadolinium-enhanced T1-weighted image shows peripheral enhancement of the lesion, with no appreciable enhancement in the predominantly myxoid center. (c) The nodule was exposed and removed with marginal excision after surgical dissection through the long head of the triceps. (d) Photomicrograph (H-E stain) shows fascia (lower left) with typical myxoid degeneration (M) predominantly in the central portion of the lesion. Note the peripheral parallel vessels at the interface between the fascia and the lesion.
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Figure 4c. Painful intramuscular nodular fasciitis in the upper arm of a 46-year-old woman. (a) Axial T2-weighted image shows a 3 x 3.5-cm hyperintense mass in the medial triceps. The mass has lower signal intensity along its periphery (arrow). (b) Coronal gadolinium-enhanced T1-weighted image shows peripheral enhancement of the lesion, with no appreciable enhancement in the predominantly myxoid center. (c) The nodule was exposed and removed with marginal excision after surgical dissection through the long head of the triceps. (d) Photomicrograph (H-E stain) shows fascia (lower left) with typical myxoid degeneration (M) predominantly in the central portion of the lesion. Note the peripheral parallel vessels at the interface between the fascia and the lesion.
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Figure 4d. Painful intramuscular nodular fasciitis in the upper arm of a 46-year-old woman. (a) Axial T2-weighted image shows a 3 x 3.5-cm hyperintense mass in the medial triceps. The mass has lower signal intensity along its periphery (arrow). (b) Coronal gadolinium-enhanced T1-weighted image shows peripheral enhancement of the lesion, with no appreciable enhancement in the predominantly myxoid center. (c) The nodule was exposed and removed with marginal excision after surgical dissection through the long head of the triceps. (d) Photomicrograph (H-E stain) shows fascia (lower left) with typical myxoid degeneration (M) predominantly in the central portion of the lesion. Note the peripheral parallel vessels at the interface between the fascia and the lesion.
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Proliferative Fasciitis and Proliferative Myositis
Proliferative fasciitis and proliferative myositis are uncommon fibroblastic reactive soft-tissue lesions (2). Proliferative fasciitis is a pseudosarcomatous, benign proliferation of myofibroblasts that is most often seen in patients older than 40 years (mean age, 54 years) (1,21). Large, plump myofibro-blasts with basophilic cytoplasm, which resemble ganglion cells and which are embedded in a fibro-myxoid stroma, are characteristic findings at microscopy (21). Like nodular fasciitis, proliferative fasciitis frequently arises in the subcutaneous tissues of the upper extremities. The lesions typically involve either the subcutaneous tissue or superficial fascia. They grow rapidly in the early stages but usually have a maximal diameter of less than 5 cm at presentation. At histopathologic analysis, they may be mistaken for sarcoma (1,21). Proliferative myositis is the deep intramuscular counterpart of proliferative fasciitis. Proliferative myositis and intramuscular lesions of nodular fasciitis have similar anatomic, pathologic, and clinical features and may be variants of the same fibroblastic disorder (22). The MR imaging appearance of proliferative fasciitis and proliferative myositis has not been well described. Local excision is the treatment of choice, but if the diagnosis is confidently made on the basis of cytologic analysis of a fine-needle aspiration specimen, a short period of observation may be reasonable as well, given the self-limited clinical course and the possibility of spontaneous lesion involution (23).
Fibroma of the Tendon Sheath
Fibroma of the tendon sheath is manifested as a slow-growing lesion in adults between the ages of 20 and 50 years (mean age, 31 years) (24). Men are affected twice as often as women. Typical features include a well-circumscribed lesion with a small diameter (< 3 cm) and a location in the extremities. The upper extremities, particularly the fingers, hands, and wrists, are the site of 82% of lesions (Fig 5) (24,25). Most of the lesions are manifested as painless soft-tissue masses. Although some investigators consider fibroma of the tendon sheath a nonneoplastic reactive lesion, a chromosomal 2;11 translocation abnormality suggestive of a neoplastic basis has been described (26).
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Figure 5a. Fibroma of the tendon sheath in the hand of a 39-year-old woman. (a) Axial T2-weighted fast SE image shows a low-signal-intensity mass on the volar aspect of the thumb (arrow). The lesion has signal isointense to that of skeletal muscle. (b) Axial gadolinium-enhanced fat-suppressed T1-weighted fast SE image shows that the heterogeneously enhanced lesion involves the flexor pollicis longus tendon (arrow), which is anteriorly displaced.
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Figure 5b. Fibroma of the tendon sheath in the hand of a 39-year-old woman. (a) Axial T2-weighted fast SE image shows a low-signal-intensity mass on the volar aspect of the thumb (arrow). The lesion has signal isointense to that of skeletal muscle. (b) Axial gadolinium-enhanced fat-suppressed T1-weighted fast SE image shows that the heterogeneously enhanced lesion involves the flexor pollicis longus tendon (arrow), which is anteriorly displaced.
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With regard to its histologic structure, fibroma of the tendon sheath tends toward hypocellularity, with scattered spindle-shaped myofibroblasts embedded in a dense collagenous stroma with slitlike vascular channels and cleftlike spaces (1,27,28). Early lesions show components of increased cellularity and myxoid change that resemble those in nodular fasciitis (1). However, paucicellular, dense fibrous connective tissue typically predominates. Some investigators believe that fibroma of the tendon sheath and giant cell tumor of the tendon sheath represent the two endpoints of a spectrum of cellular proliferation (29,30). Lesions of the two types are similar in size, location, and gross morphologic features. Fibroma and giant cell tumor of the tendon sheath occur in similar patient populations and commonly are manifested as painless slow-growing masses in the peripheral extremities, particularly the hands, where they may interfere mechanically with tendon or joint function (30–32). Local excision is the treatment of choice for fibroma of the tendon sheath. A recurrence rate as high as 24% has been reported (24).
At MR imaging, attachment of the tumor to a tendon or tendon sheath is obvious in most cases. The tumor typically has signal intensity that is equal to or lower than that of skeletal muscle on T1- and T2-weighted images (Fig 6). In the case series described by Fox et al, 50% of lesions had signal intensity equal to or lower than that of skeletal muscle on T2-weighted images, a finding that likely is attributable to the high quantity of collagen in many of these tumors (33). Areas of increased signal intensity are seen in lesions with components of increased cellularity or myxoid change (33). The contrast enhancement pattern is variable, with some lesions demonstrating no appreciable enhancement, whereas others show moderate to marked enhancement (33). If a fibroma of the tendon sheath has hypointense signal on all MR images, it may have imaging features that overlap with those of the localized type of giant cell tumor of the tendon sheath. Hemosiderin deposition—a histopathologic feature of giant cell tumor—may help distinguish between the two lesions at MR imaging. Because of hemosiderin deposition, gradient-echo images of a giant cell tumor of the tendon sheath may show a "blooming artifact" of accentuated low signal intensity (34), a feature that is not expected in a fibroma of the tendon sheath.
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Figure 6a. Fibroma of the tendon sheath in the foot of a 26-year-old woman. (a) Short-axis T2-weighted image depicts a mass, dorsal to the third metatarsal bone of the right foot, with signal that is hypointense to that of skeletal muscle. The anatomic location and signal intensity of the lesion are suggestive of a fibroma or giant cell tumor of the tendon sheath. (b) Photomicrograph (H-E stain) at high power shows a well-delineated mass that is hypocellular and contains a dense collagenous matrix that surrounds a slitlike vessel (arrow) and scattered spindle-shaped fibroblasts.
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Figure 6b. Fibroma of the tendon sheath in the foot of a 26-year-old woman. (a) Short-axis T2-weighted image depicts a mass, dorsal to the third metatarsal bone of the right foot, with signal that is hypointense to that of skeletal muscle. The anatomic location and signal intensity of the lesion are suggestive of a fibroma or giant cell tumor of the tendon sheath. (b) Photomicrograph (H-E stain) at high power shows a well-delineated mass that is hypocellular and contains a dense collagenous matrix that surrounds a slitlike vessel (arrow) and scattered spindle-shaped fibroblasts.
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Keloid and Hypertrophic Scar
Keloids and hypertrophic scars are benign fibroblastic proliferations that arise from the dermis (Fig 7). Keloids have morphologic and pathologic features that overlap with those of hypertrophic scars, but they may be distinguished from hypertrophic scars by their growth beyond the margins of an injury site, the presence of keloid collagen, less frequent uptake of stain indicative of smooth muscle actin, and higher recurrence rates (35). Keloids are hypocellular, densely collagenous lesions predominantly composed of type I collagen (1). The abundant collagen accounts for the short T2 relaxation times of keloids. Persons of African and Chinese descent have an increased risk for these fibrous lesions. Keloids most frequently are seen in patients aged 15–45 years and commonly involve the face, shoulders, forearms, and hands (1). The lesions may arise in association with trauma, infection, or connective tissue diseases, and they tend to occur where there is increased skin tension. Keloids and hypertrophic scars may produce a mass effect, pruritus, and paresthesia, but they typically are secondary to cosmetic deformities (36). Keloids do not spontaneously regress, and they tend to recur after surgical excision. Therefore, surgery has been combined with topical injection of corticosteroids or postsurgical radiation therapy to decrease recurrence (1).
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Figure 7a. Hypertrophic scar in the foot of a 37-year-old woman. (a, b) Sagittal T1-weighted image (a) and short inversion time inversion recovery image (b) demonstrate an elongated low-signal-intensity mass (*) that has arisen in the skin on the plantar aspect of the foot. (c) Photomicrograph (H-E stain) at low power shows the dense collagenous content of the lesion, which accounts for its low signal intensity in a and b; a disorganized spindled fibroblastic cell proliferation oriented in a predominantly horizontal direction, deep to the epidermis (E); vertically oriented vessels (*); and the absence of thick keloid-like collagenous bands.
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Figure 7b. Hypertrophic scar in the foot of a 37-year-old woman. (a, b) Sagittal T1-weighted image (a) and short inversion time inversion recovery image (b) demonstrate an elongated low-signal-intensity mass (*) that has arisen in the skin on the plantar aspect of the foot. (c) Photomicrograph (H-E stain) at low power shows the dense collagenous content of the lesion, which accounts for its low signal intensity in a and b; a disorganized spindled fibroblastic cell proliferation oriented in a predominantly horizontal direction, deep to the epidermis (E); vertically oriented vessels (*); and the absence of thick keloid-like collagenous bands.
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Figure 7c. Hypertrophic scar in the foot of a 37-year-old woman. (a, b) Sagittal T1-weighted image (a) and short inversion time inversion recovery image (b) demonstrate an elongated low-signal-intensity mass (*) that has arisen in the skin on the plantar aspect of the foot. (c) Photomicrograph (H-E stain) at low power shows the dense collagenous content of the lesion, which accounts for its low signal intensity in a and b; a disorganized spindled fibroblastic cell proliferation oriented in a predominantly horizontal direction, deep to the epidermis (E); vertically oriented vessels (*); and the absence of thick keloid-like collagenous bands.
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Elastofibroma
Elastofibroma is a degenerative or reactive fibrous pseudotumor that is generally considered to result from chronic mechanical irritation (1). However, a genetic predisposition also has been described (37), and the identification of clonal chromosomal changes has led to a suggestion that the lesion may represent a fibroblastic neoplasm (38). Elastofibroma is a slow-growing lesion that is most frequently encountered in the connective tissue between the posterior chest wall and the inferomedial border of the scapula, usually in patients older than 55 years (mean age, 70 years) (37). Autopsy studies have shown subscapular elastofibromas in 11.2% of men and 24.4% of women older than 55 years (39). Computed tomography of the chest has demonstrated elastofibromas in 2% of patients older than 60 years (40). The incidental detection of elastofibroma with fluorine 18 fluorodeoxyglucose positron emission tomography also has been described (41). Subscapular elastofibromas are bilateral in about 25% of cases (42,43). Extrascapular sites, which are much less common, include regions of the greater trochanter at the hip and the olecranon at the elbow (37). Symptomatic lesions generally have a diameter greater than 5 cm. The most commonly reported clinical symptoms are stiffness (approximately 25% of patients) and pain (10% of patients) (37). Elastofibromas consist of accumulations of collagen and abnormal elastic fibers, with interspersed fat cells and spindle-shaped fibroblasts and myofibroblasts (Fig 8) (1,39). The differential diagnosis of lesions that are relatively hypocellular and contain abundant collagen includes extraabdominal desmoid tumor, as well as neurofibroma and malignant fibrous histiocytoma.
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Figure 8a. Subscapular elastofibroma. (a) Gross specimen resected from an 81-year-old woman shows an admixture of fibrous tissue (white) with fat (yellow). (b) Low-power photomicrograph (H-E stain) demonstrates fibromyxoid stroma with fat infiltration (white) and scattered elastic fibers (bright red).
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Figure 8b. Subscapular elastofibroma. (a) Gross specimen resected from an 81-year-old woman shows an admixture of fibrous tissue (white) with fat (yellow). (b) Low-power photomicrograph (H-E stain) demonstrates fibromyxoid stroma with fat infiltration (white) and scattered elastic fibers (bright red).
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On MR images, elastofibromas are typically well defined, heterogeneous soft-tissue masses with signal intensity similar to that of skeletal muscle and frequently with intermixed linear or curvilinear streaks of fat signal intensity, findings representative of the histologic constituents of the lesion (Fig 9) (44,45). Gadolinium-related contrast enhancement is typically heterogeneous. Given a characteristic lesion location and patient age at presentation, and signal characteristics of elastofibroma, a prospective MR imaging diagnosis often can be made with a high degree of confidence, particularly when bilateral lesions are identified (46,47). Local excision is the treatment of choice for symptomatic lesions. Local recurrence is rare and likely is due to incomplete excision (37). To our knowledge, no reports of malignant transformation exist in the literature (1).
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Figure 9a. Subscapular elastofibroma in a 57-year-old woman. (a) Axial T1-weighted image of the left upper back shows a lenticular mass (arrow), deep to the latissimus dorsi and serratus anterior muscles (arrowhead), that contains hyperintense linear streaks of entrapped fat. (b) T2-weighted fast SE image without fat suppression depicts the lesion (arrow) with signal predominantly isointense to that of skeletal muscle.
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Figure 9b. Subscapular elastofibroma in a 57-year-old woman. (a) Axial T1-weighted image of the left upper back shows a lenticular mass (arrow), deep to the latissimus dorsi and serratus anterior muscles (arrowhead), that contains hyperintense linear streaks of entrapped fat. (b) T2-weighted fast SE image without fat suppression depicts the lesion (arrow) with signal predominantly isointense to that of skeletal muscle.
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Fibromatoses
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Superficial Fibromatosis
Soft-tissue fibromatoses are divided into two major groups: superficial (fascial) and deep (musculoaponeurotic) lesions. Although soft-tissue fibromatoses are benign and have no metastatic potential, their biologic behavior is somewhat aggressive—between that of benign fibrous proliferations (eg, nodular fasciitis) and fibrosarcoma. Superficial fibromatoses arise from fascia or aponeuroses at palmar, plantar, penile (Peyronie disease), and knuckle pad locations (1,3). At microscopy, the lesions contain spindle-shaped myofibroblastic cells, dense deposits of intercellular collagen fibers, variable amounts of extracellular myxoid matrix, and compressed and elongated vessels (1).
Palmar fibromatosis (Dupuytren disease) is the most common type of superficial fibromatosis. This slow-growing lesion affects the aponeurosis along the volar aspect of the hand, usually in patients older than 30 years (Fig 10) (1). The lesions occur predominantly in men, and approximately 50% of cases occur in bilateral locations (48). The collagenous cords may produce flexion contractures that typically affect flexor tendons of the fourth and fifth fingers (48). Early-stage mitotically active lesions have high signal intensity on T2-weighted images, are predominantly cellular, and have higher recurrence rates (70%) than more mature lesions, which have a higher collagen content (7,49). MR imaging may be helpful for planning the optimal timing of surgical treatment of palmar fibromatosis, given that mature collagenous lesions with relatively low signal intensity on T2-weighted images may be less likely to locally recur than are more cellular lesions with higher signal intensity on T2-weighted images (5,7).
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Figure 10a. Palmar fibromatosis in a 44-year-old woman. (a) Sagittal T1-weighted image depicts a 1-cm-long fusiform lesion (arrowhead) along the palmar aponeurosis at the level of the distal fifth metacarpal. (b) Axial T2-weighted MR image shows low signal intensity in the lesion (arrowhead), which is superficial to the flexor tendon (arrow). (c) High-power photomicrograph (H-E stain) shows a relatively hypocellular, infiltrative aponeurotic tumor composed of fibroblasts, elongated vessels, and extracellular keloidal collagen (arrows).
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Figure 10b. Palmar fibromatosis in a 44-year-old woman. (a) Sagittal T1-weighted image depicts a 1-cm-long fusiform lesion (arrowhead) along the palmar aponeurosis at the level of the distal fifth metacarpal. (b) Axial T2-weighted MR image shows low signal intensity in the lesion (arrowhead), which is superficial to the flexor tendon (arrow). (c) High-power photomicrograph (H-E stain) shows a relatively hypocellular, infiltrative aponeurotic tumor composed of fibroblasts, elongated vessels, and extracellular keloidal collagen (arrows).
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Figure 10c. Palmar fibromatosis in a 44-year-old woman. (a) Sagittal T1-weighted image depicts a 1-cm-long fusiform lesion (arrowhead) along the palmar aponeurosis at the level of the distal fifth metacarpal. (b) Axial T2-weighted MR image shows low signal intensity in the lesion (arrowhead), which is superficial to the flexor tendon (arrow). (c) High-power photomicrograph (H-E stain) shows a relatively hypocellular, infiltrative aponeurotic tumor composed of fibroblasts, elongated vessels, and extracellular keloidal collagen (arrows).
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Plantar fibromatosis (Ledderhose disease) may affect both children and adults, with bilateral lesions occurring in 20%–50% of cases (50). Men are affected twice as often as women, and associated palmar fibromatosis is seen in 10%–65% of patients (50). Nodules or masses of plantar fibromatosis are typically located in the middle to medial aspect of the plantar arch and may extend to involve the skin or deep structures of the foot. Although trauma has commonly been considered a possible cause of plantar fibromatosis, the pathogenesis of the lesion is likely multifactorial. Cytogenetic studies have shown chromosomal aberrations of trisomy 8 and trisomy 14 within some plantar lesions (51). The lesions may be symptomatic because of a mass effect or invasion of adjacent muscles or neurovascular structures. At MR imaging, plantar fibromatosis typically has heterogeneous signal intensity, but the signal in the plantar lesions is predominantly isointense or hypointense to that in skeletal muscle on T1- and T2-weighted images (Fig 11) (52). Local excision with a wide margin is the treatment of choice for painful or disabling lesions. In addition, some symptomatic lesions have been treated effectively with an intralesional steroid injection or with postoperative adjuvant radiation therapy (53). However, radiation therapy must be used selectively, as it may increase the risk of posttreatment functional impairment (54).
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Figure 11a. Plantar fibromatosis along the aponeurosis superficial to the flexor digitorum brevis muscle. (a) Short-axis T1-weighted image shows a lesion (arrow) with foci of intermediate signal intensity corresponding to cellular areas and foci of low signal intensity corresponding to collagenous areas (arrowheads). (b) Sagittal short inversion time inversion recovery MR image shows the lesion (large arrow) with heterogeneous signal intensity and linear extension (small arrow) along the plantar aponeurosis (arrowheads). (c) Incision through the plantar surface of the foot reveals a firm, glistening nodule (arrows) of the medial plantar aponeurosis.
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Figure 11b. Plantar fibromatosis along the aponeurosis superficial to the flexor digitorum brevis muscle. (a) Short-axis T1-weighted image shows a lesion (arrow) with foci of intermediate signal intensity corresponding to cellular areas and foci of low signal intensity corresponding to collagenous areas (arrowheads). (b) Sagittal short inversion time inversion recovery MR image shows the lesion (large arrow) with heterogeneous signal intensity and linear extension (small arrow) along the plantar aponeurosis (arrowheads). (c) Incision through the plantar surface of the foot reveals a firm, glistening nodule (arrows) of the medial plantar aponeurosis.
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Figure 11c. Plantar fibromatosis along the aponeurosis superficial to the flexor digitorum brevis muscle. (a) Short-axis T1-weighted image shows a lesion (arrow) with foci of intermediate signal intensity corresponding to cellular areas and foci of low signal intensity corresponding to collagenous areas (arrowheads). (b) Sagittal short inversion time inversion recovery MR image shows the lesion (large arrow) with heterogeneous signal intensity and linear extension (small arrow) along the plantar aponeurosis (arrowheads). (c) Incision through the plantar surface of the foot reveals a firm, glistening nodule (arrows) of the medial plantar aponeurosis.
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Deep Fibromatosis
Deep fibromatoses, which have a fibrotic bandlike or tendonlike consistency, are also known as desmoid tumors (1,55). Desmoid tumors originate from connective tissue in muscle, fascia, or aponeuroses and occur mostly in adults aged 25–35 years (1,3,56,57). Genetic differences between superficial and deep lesions have been described, and these differences may account for the often more aggressive behavior of deep lesions (58). Trisomies at chromosomes 8 and 20 have been identified in many cases of deep fibromatosis, and trisomy 8 may be associated with an increased risk for tumor recurrence (59).
Deep fibromatoses are classified according to their intraabdominal, abdominal, or extraabdominal location. The category of intraabdominal fibromatoses includes tumors that arise within the pelvis and mesentery. Although most cases of mesenteric fibromatosis are sporadic, some are associated with familial adenomatous polyposis (Gardner syndrome) (1). Approximately 10% of patients with Gardner syndrome also have fibromatosis, which typically is of the intraabdominal type and which may be associated with mutations of the APC gene on chromosome 5q22 (60,61). These intraabdominal desmoid tumors are usually located in the small-bowel mesentery, may cause bowel obstruction, and frequently recur after attempted surgical resection (61).
Abdominal fibromatosis is a distinct entity that tends to occur in women during pregnancy or within the 1st year after delivery and in women who use oral contraceptives. This pattern of occurrence may indicate that estrogen is a growth factor for the fibroblastic tumors (1,62). The rectus abdominis and internal oblique muscles of the anterior abdominal wall are most frequently affected (Fig 12) (1).
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Figure 12a. Abdominal desmoid tumor in a 38-year-old woman. (a) Axial T2-weighted image shows a large heterogeneous mass (arrow) that contains regions of intermediate to low signal intensity in the abdominal wall on the left side. (b) Sagittal gadolinium-enhanced T1-weighted image shows an enhanced tumor (arrow) that involves fascial layers of the left rectus abdominis muscle. (c) Photograph of the resected gross specimen demonstrates a well-circumscribed mass with a heterogeneous and fibrous "fish flesh" appearance.
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Figure 12b. Abdominal desmoid tumor in a 38-year-old woman. (a) Axial T2-weighted image shows a large heterogeneous mass (arrow) that contains regions of intermediate to low signal intensity in the abdominal wall on the left side. (b) Sagittal gadolinium-enhanced T1-weighted image shows an enhanced tumor (arrow) that involves fascial layers of the left rectus abdominis muscle. (c) Photograph of the resected gross specimen demonstrates a well-circumscribed mass with a heterogeneous and fibrous "fish flesh" appearance.
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Figure 12c. Abdominal desmoid tumor in a 38-year-old woman. (a) Axial T2-weighted image shows a large heterogeneous mass (arrow) that contains regions of intermediate to low signal intensity in the abdominal wall on the left side. (b) Sagittal gadolinium-enhanced T1-weighted image shows an enhanced tumor (arrow) that involves fascial layers of the left rectus abdominis muscle. (c) Photograph of the resected gross specimen demonstrates a well-circumscribed mass with a heterogeneous and fibrous "fish flesh" appearance.
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Extraabdominal fibromatosis most frequently arises between or adjacent to the fasciae and muscles of the shoulder, chest wall, back, thigh, and knee (1,56,57). The aggressively infiltrative tumors usually have a diameter of more than 5 cm at presentation, grow rapidly, and frequently extend along muscle. They are typically solitary lesions, but multiple lesions are seen in up to 15% of cases (63). The most aggressive lesions usually occur in patients younger than 20 years, among whom the local recurrence rate may be as high as 87% (Fig 13) (64).
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Figure 13a. Aggressive fibromatosis in an 18-year-old man. (a) Axial T2-weighted image shows the subcutaneous origin of a relatively cellular tumor (arrow) located posterior to the infraspinatus and deltoid muscles. (b) Sagittal gadolinium-enhanced fat-suppressed T1-weighted image, obtained within 1 year after lesion excision, shows an enhanced and infiltrative recurrent mass with spiculated margins (arrowheads) that extends posterior and inferior to the scapula. Note the deep intra- and intermuscular component (arrow) located between the supraspinatus and subscapularis muscles.
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Figure 13b. Aggressive fibromatosis in an 18-year-old man. (a) Axial T2-weighted image shows the subcutaneous origin of a relatively cellular tumor (arrow) located posterior to the infraspinatus and deltoid muscles. (b) Sagittal gadolinium-enhanced fat-suppressed T1-weighted image, obtained within 1 year after lesion excision, shows an enhanced and infiltrative recurrent mass with spiculated margins (arrowheads) that extends posterior and inferior to the scapula. Note the deep intra- and intermuscular component (arrow) located between the supraspinatus and subscapularis muscles.
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MR imaging, which provides better soft-tissue contrast resolution than do other imaging modalities, allows an accurate evaluation of the relationship between the tumor and surrounding vital structures such as vessels, nerves, and bones. An infiltrative border in the form of a fascial tail is frequently observed (approximately 80% of cases, in our experience) on MR images of deep fibromatosis (Fig 14). Fibromatosis usually has heterogeneous signal intensity that likely reflects the different amounts and variable distribution of spindle-shaped cells, extracellular collagen, and myxoid matrix (55,65). The histologic features of desmoid tumors change over time, and the alterations may be depicted on MR images. Early-stage lesions are more cellular and have a predominantly hyperintense signal on T2-weighted MR images. As desmoid tumors evolve, collagen deposition increases and cellularity and extracellular spaces decrease, with a resultant decrease in signal intensity on T2-weighted images (66). Tumor enhancement with gadolinium-related contrast is typically moderate to marked in intensity (67). On T2-weighted spin-echo (SE) images, the predominant signal intensity of most tumors is intermediate, between that of skeletal muscle and that of subcutaneous fat (6). In 86% of cases of fibromatosis, T2-weighted images depict hypointense bands that likely correspond to dense conglomerations of collagen bundles seen at histologic analysis (Fig 15) (6). These collagen bundles are not enhanced by contrast material. Such features are suggestive of the correct preoperative diagnosis. However, the MR imaging–based differential diagnosis may include other infiltrative lesions with predominant low signal intensity on T2-weighted images, such as malignant fibrous histiocytoma, fibrosarcoma, densely calcified masses, and giant cell tumor of the tendon sheath.
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Figure 14a. Extraabdominal desmoid tumor in a 46-year-old man with a history of spinal fusion surgery. (a) Axial T2-weighted fast SE image shows a well-circumscribed mass (arrow), centered between the posterior layer of the thoracolumbar fascia and the multifidus muscle, that contains collagenous bands of low signal intensity that are most visible medially. (b) Sagittal T2-weighted fast SE image shows an infiltrative mass between muscle and fascia at the T12-L1 level that extends linearly along the fascia (arrowhead). (c) Photomicrograph (H-E stain) shows a poorly circumscribed proliferation of spindle cells and ectatic blood vessels. The lesion (*) has infiltrated adipose tissue (arrow) and skeletal muscle (M).
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Figure 14b. Extraabdominal desmoid tumor in a 46-year-old man with a history of spinal fusion surgery. (a) Axial T2-weighted fast SE image shows a well-circumscribed mass (arrow), centered between the posterior layer of the thoracolumbar fascia and the multifidus muscle, that contains collagenous bands of low signal intensity that are most visible medially. (b) Sagittal T2-weighted fast SE image shows an infiltrative mass between muscle and fascia at the T12-L1 level that extends linearly along the fascia (arrowhead). (c) Photomicrograph (H-E stain) shows a poorly circumscribed proliferation of spindle cells and ectatic blood vessels. The lesion (*) has infiltrated adipose tissue (arrow) and skeletal muscle (M).
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Figure 14c. Extraabdominal desmoid tumor in a 46-year-old man with a history of spinal fusion surgery. (a) Axial T2-weighted fast SE image shows a well-circumscribed mass (arrow), centered between the posterior layer of the thoracolumbar fascia and the multifidus muscle, that contains collagenous bands of low signal intensity that are most visible medially. (b) Sagittal T2-weighted fast SE image shows an infiltrative mass between muscle and fascia at the T12-L1 level that extends linearly along the fascia (arrowhead). (c) Photomicrograph (H-E stain) shows a poorly circumscribed proliferation of spindle cells and ectatic blood vessels. The lesion (*) has infiltrated adipose tissue (arrow) and skeletal muscle (M).
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Figure 15a. Extraabdominal desmoid tumor in the neck of a 26-year-old woman. (a) Axial T2-weighted fat-suppressed fast SE image shows a predominantly intermuscular mass with prominent low-signal-intensity fibrous bands (arrow) surrounded by cellular regions of higher signal intensity. (b) Sagittal gadolinium-enhanced T1-weighted image shows longitudinal extension of the enhanced tumor (arrows) along the fascia, and nonenhanced fibrous bands (arrowheads). (c) Gross specimen photograph demonstrates the infiltrative border (arrow) of the fibroblastic tumor, with multiple fibrous bands (arrowheads). (d) Photomicrograph (H-E stain) at intermediate power shows bland myofibroblasts parallel to elongated vessels, and keloidal collagen (pink).
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Figure 15b. Extraabdominal desmoid tumor in the neck of a 26-year-old woman. (a) Axial T2-weighted fat-suppressed fast SE image shows a predominantly intermuscular mass with prominent low-signal-intensity fibrous bands (arrow) surrounded by cellular regions of higher signal intensity. (b) Sagittal gadolinium-enhanced T1-weighted image shows longitudinal extension of the enhanced tumor (arrows) along the fascia, and nonenhanced fibrous bands (arrowheads). (c) Gross specimen photograph demonstrates the infiltrative border (arrow) of the fibroblastic tumor, with multiple fibrous bands (arrowheads). (d) Photomicrograph (H-E stain) at intermediate power shows bland myofibroblasts parallel to elongated vessels, and keloidal collagen (pink).
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Figure 15c. Extraabdominal desmoid tumor in the neck of a 26-year-old woman. (a) Axial T2-weighted fat-suppressed fast SE image shows a predominantly intermuscular mass with prominent low-signal-intensity fibrous bands (arrow) surrounded by cellular regions of higher signal intensity. (b) Sagittal gadolinium-enhanced T1-weighted image shows longitudinal extension of the enhanced tumor (arrows) along the fascia, and nonenhanced fibrous bands (arrowheads). (c) Gross specimen photograph demonstrates the infiltrative border (arrow) of the fibroblastic tumor, with multiple fibrous bands (arrowheads). (d) Photomicrograph (H-E stain) at intermediate power shows bland myofibroblasts parallel to elongated vessels, and keloidal collagen (pink).
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Abstract
LEARNING OBJECTIVES
