Gastrointestinal stromal tumour with a KIT exon 11 mutation presenting as a paratesticular mass.

Gastrointestinal stromal tumours (GISTs) are sarcomas arising in the gastrointestinal tract. They are characterised by a gain in function mutation of the KIT oncogene and the majority express the receptor tyrosine kinase KIT, which can be detected by the immunohistochemical stain CD117. Patients with a GIST present with symptoms such as abdominal pain or gastrointestinal bleeding, or may be asymptomatic. We describe the clinical history and pathological features of a patient with a GIST who presented with a paratesticular mass which, to our knowledge, has never previously been reported. With the development of new drugs to treat GISTs, the knowledge of the type of mutations may in the future prove helpful in determining optimal treatment strategies and prognosis.

Chondroid lipoma. A unique tumor simulating liposarcoma and myxoid chondrosarcoma.

We report 20 cases of a peculiar fatty tumor that occurred in 16 female and four male patients who were 14-70 years old (median, 36 years). Most lesions were situated in the subcutis, superficial muscular fascia, or skeletal muscle of the limbs and limb girdles (15), trunk (3), and the head and neck (2). They were 1.5-11 cm in size (median, 4 cm) and usually described as yellow (13 of 15) and encapsulated (13 of 15). Microscopically they were well circumscribed and consisted of nests, strands, and sheets of eosinophilic and vacuolated cells, which contained glycogen and fat droplets, resembling brown fat cells, lipoblasts and chondroblasts. In all cases there was a variable background of mature adipose tissue associated with a prominent, partially fibrinous to hyalinized myxoid matrix that contained acid mucopolysaccharides usually resistant to hyaluronidase digestion. Several cases had foci of serous atrophy, perivascular fibrosis, and small thrombi; two were focally calcified. The lesions stained for S100 protein (11 of 12), vimentin (10 of 11), and CD68 antigen with KP1 (9 of 11); focal staining for keratin was also seen (4 of 11), but none stained for epithelial membrane antigen or actin or with HMB45. Follow-up in 12 cases (median, 9.5 years) revealed no local recurrences or metastases. Despite its deep location and atypical cellular features, the lesion's nonaggressive behavior suggests it is benign and neither a myxoid liposarcoma nor a myxoid chondrosarcoma, with which it is most frequently confused. The presence of glycogen in vacuolated fat cells is similar to brown fat, and the presence of sulfated stromal mucins supports focal chondroid differentiation. Although the pathogenesis remains uncertain, a lipoma with hibernomatous features, myxoid change, chondroid metaplasia, and secondary degenerative features is favored over a lipogranulomatous process.

Primary angiosarcoma of the spleen. A clinicopathologic study of 40 cases.

Forty primary splenic angiosarcomas occurring in 21 men and 19 women, 19-84 years old (median 59 years) are reported. Patients presented with splenomegaly (35 of 38, 92%), abdominal pain (33 of 40, 83%), and systemic symptoms such as fatigue (2 of 40, 5%), fever (4 of 40, 10%), and/or weight loss (16 of 40, 40%). Five (13%) experienced splenic rupture associated with hemoperitoneum. Abnormal laboratory findings included cytopenia (31 of 34, 91%), leukocytosis (8 of 21, 38%), and thrombocytosis (1/39, 3%). Most spleens weighed 500-1,000 g (mean, 1,180 g). The cut splenic surfaces showed multiple hemorrhagic nodules that were frequently associated with infarction, although some had a diffuse pattern of involvement. Microscopically, there were a variety of histologic patterns displayed by the vasoformative component. A honeycomb or sponge-like pattern was common in some, whereas others simulated a cavernous hemangioma or normal splenic sinuses (pseudosinusoidal pattern). Papillary endothelial tufts and solid proliferations of spindled to round to epithelioid cells were also seen. Factor VIII-related antigen was detected in 19 of 23 cases, BMA-120 in 18 of 23, UEA-1 receptor in 18 of 23, and vimentin in 23 of 23 as well as CD68 antigen in 1 of 23 cases. S-100 protein and cytokeratin were not found in any of the 23 cases studied. Metastases in 22 of 32 patients (69%) were to the liver (13 patients), bone or bone marrow (7 patients), lymph nodes (1 patient), and brain (1 patient). Three patients had concomitant malignancies and one had a prior history of a mixed B-cell lymphoma 5 years previously that had been treated with chemotherapy. Follow-up in 38 patients revealed that 30 (79%) are dead at a median interval of 6 months (range 0-48 months) and 8 are alive 5-21 months after diagnosis. These findings indicate that splenic angiosarcoma is an aggressive neoplasm with a high metastatic rate and an abysmal prognosis. Recognition of the wide range of histologic patterns is of diagnostic value but no apparent prognostic significance.

Fetal rhabdomyoma of the head and neck: a clinicopathologic and immunophenotypic study of 24 cases.

Twenty-four fetal rhabdomyomas (FRMs) of the head and neck occurring in 16 male and seven female patients (sex unknown in one), ranging from 3 days to 58 years of age (median, 4.5 years) are reported. Ten patients (42%) were < or = 1 year old, six lesions (25%) were congenital, and 11 lesions (46%) occurred in patients > or = 15 years of age. The median tumor size was 3.0 cm (range, 1.0 to 12.5 cm). The FRMs presented as well-defined, solitary masses arising within the soft tissue or mucosa (2:1) of the head and neck. The median follow-up in 15 cases was 48 months (range, 2 months to 52 years) after diagnosis. With the exception of one patient with a local recurrence, all patients were either alive and well or dead of unrelated causes. Eight cases, regarded as "classic" FRM, consisted predominantly of bland, primitive spindled cells associated with delicate, elongated skeletal muscle cells reminiscent of fetal myotubules that were haphazardly arranged in an abundant fibromyxoid stroma. The remaining 16 cases, designated as "intermediate" FRM, displayed both a greater degree and a greater number of cells with skeletal muscle differentiation as well as a variety of distinctive cytologic and architectural features. These included the presence of large, ganglion cell-like rhabdomyoblasts with vesicular nuclei and prominent nucleoli, interlacing ribbon or strap-like rhabdomyoblasts with deeply acidophilic cytoplasm, broad bundles of more delicate spindled rhabdomyoblasts arranged in fascicles simulating smooth muscle, an occasional plexiform pattern with infiltration of adipose tissue and skeletal muscle, focal intimate association with peripheral nerves, and rare areas of fibroblastic proliferation. Mitoses were not found in 19 of the 24 FRM cases, but in five tumors there were 1 to 14 mitoses/50 high-power fields. Marked nuclear atypia, anaplasia, and a "cambium layer" were uniformly absent. The FRMs typically stained for myoglobin, desmin, and muscle-specific actin with focal or rare staining for vimentin, smooth muscle actin, S-100 protein, glial fibrillary acidic protein, and Leu-7. Cytokeratin, epithelial membrane antigen, and CD68 antigen (with KP1) were not detected. This study expands on previous reports of FRM and demonstrates that it has both a broader age range and histologic spectrum than previously recognized. The mitotic rates of FRM as well as certain histologic features overlap with rhabdomyosarcoma; the lack of marked nuclear atypia is an important distinguishing feature.(ABSTRACT TRUNCATED AT 400 WORDS)

From the archives of the AFIP. Extraskeletal osseous and cartilaginous tumors of the extremities.

Extraskeletal osseous and cartilaginous tumors and tumorlike conditions of the extremities can often be differentiated radiologically; for those that cannot, knowledge of the spectrum of lesions will allow a suitably ordered differential diagnosis. Of the osseous lesions--myositis ossificans, fibro-osseous pseudotumor, fibrodysplasia ossificans progressiva, soft-tissue osteoma, and extraskeletal osteosarcoma--all but myositis ossificans are relatively rare. Myositis ossificans has a distinct mineralization pattern that can be observed radiologically as a peripheral rim of lamellar bone. Fibro-osseous pseudotumor typically occurs in the digits of the hand and lacks the well-defined zoning pattern of myositis ossificans. The cartilaginous entities include the true tumors, soft-tissue chondroma and extraskeletal chondrosarcoma, and the tumorlike process, synovial osteochondromatosis. The tumors are relatively rare; synovial osteochondromatosis commonly affects middle-aged men, especially in the knee, and is associated with osteoarthritis. The differential diagnosis for these extraskeletal osseous and cartilaginous lesions includes soft-tissue sarcoma, benign mesenchymoma, malignant mesenchymoma (rare), calcified tophi in gout, melorheostosis (rare), pilomatricoma (rare), and tumoral calcinosis (rare).

Synovial sarcoma of the abdominal wall.

BACKGROUND: Synovial sarcoma usually arises in the extremities and in close proximity to large joints. Reported examples arising in the anterior abdominal wall are rare. Because most accounts from this location consist of case reports, neither clinical nor prognostic features have been well delineated. METHODS: Twenty-seven synovial sarcomas of the abdominal wall (SSAW), retrieved from the Soft Tissue Registry of the Armed Forces Institute of Pathology, were reviewed and analyzed retrospectively. Immunohistochemical stains were performed in 18 cases. RESULTS: There were specimens from 12 male and 15 female patients, ranging in age from 8 to 58 years (median, 23 years). The tumors were classified as biphasic (14), predominantly monophasic fibrous (8), and poorly differentiated (5) types. The neoplasms occasionally were cystic and typically reacted, at least focally, with antibodies directed against keratin and/or epithelial membrane antigen. Eight tumors were smaller than 5 cm.; 17 tumors were 5 cm or larger in size. Dimensions were not recorded in two cases. Follow-up, ranging from 1 to 264 months, was obtained in 18 cases. Nine individuals were alive and well and eight were dead of disease at median follow-up intervals of 98 and 26 months, respectively. One patient was dead with disease, possibly secondary to chemotherapy-related causes. All nine patients who have died had clinical evidence of metastatic disease. Patients who presented with tumors 5 cm or larger had a less favorable outcome than whose with tumors smaller than 5 cm. (58% versus 40% mortality). A positive correlation was noted between increased mitotic activity and the mortality rate. Although patients with biphasic and predominantly monophasic fibrous tumors had a similar mortality rate (40% for both groups), patients with poorly differentiated synovial sarcoma fared worse (100% mortality). In general, poorly differentiated synovial sarcomas had a higher mitotic rate than either biphasic or monophasic fibrous examples. No appreciable difference in survival was evident based on the age at presentation (< 15 versus > or = 15 years of age). CONCLUSIONS: The survival rate for patients with SSAW is similar to that reported for synovial sarcoma in general. A high mitotic rate and the poorly differentiated subtype of synovial sarcoma both were associated with a poor prognosis and, to some extent, appear interrelated. Less favorable behavior also was noted when the tumors were large (> or = 5 cm). Pluripotential or arthrogenous mesenchyme may be implicated in the pathogenesis of these tumors.

Dedifferentiated liposarcoma of the extremities: imaging findings in four patients.

OBJECTIVE: The term "dedifferentiated" liposarcoma is used to describe a distinctive lesion in which a well-differentiated liposarcoma is juxtaposed with a high-grade nonlipogenic sarcoma. Dedifferentiated liposarcoma is probably the most common of all the dedifferentiated sarcomas, occurring almost exclusively in the mediastinum, the retroperitoneum, and the inguinal/paratesticular regions. We report the imaging findings in four cases of dedifferentiated liposarcoma of the lower extremities. MATERIALS AND METHODS: The radiologic images and clinical histories of four patients with histologically verified dedifferentiated liposarcoma were retrospectively studied. The mean age of the patients was 61 years (range, 33-79 years). All lesions occurred in the thigh. Spin-echo MR images were available for review in two cases and CT scans in the two remaining cases. Plain radiographs were available in all cases. RESULTS: All lesions were large, with a mean maximum size of 24 cm (range, 12-30 cm), and had a significant fatty component radiologically. Both MR and CT showed a well-delineated fatty component of the lesions and a closely apposed nonfatty region. Radiographs showed well-defined bone within one lesion, bone and amorphous calcification in another, and a single punctate calcification in a third. Two patients had a history of excision of a lipomatous lesion in the region of the mass. One patient had pulmonary metastases. CONCLUSION: The potential for deep well-differentiated fatty tumors of the extremities to dedifferentiate is not generally recognized. Although the different types of liposarcoma cannot be reliably distinguished with imaging studies, a well-defined nonlipomatous mass juxtaposed with a predominantly fatty tumor is suggestive of a dedifferentiated liposarcoma.

Adult rhabdomyoma of the head and neck: a clinicopathologic and immunophenotypic study.

Twenty-seven cases of adult rhabdomyoma (ARM) of the head and neck are reported. The 20 male and seven female patients ranged in age from 33 to 80 years (median age, 60 years). Symptoms included airway obstruction and a mass within the mucosa or soft tissue. Median tumor size was 3.0 cm (range, 1.5 to 7.5 cm). Seven patients (26%) presented with multinodular tumors and one tumor was multicentric. Follow-up was available in 19 cases and ranged from 2 months to 18.5 years after diagnosis (median, 6.0 years). Lesions recurred locally in eight cases (42%) 2 to 11 years after diagnosis (median, 6 years). One recurrence was multicentric. Histologically, ARM was composed of closely packed, large polygonal cells having abundant, eosinophilic, granular, or vacuolated glycogen-rich cytoplasm with focal cross-striations. Immunohistochemical stains confirmed skeletal muscle differentiation; the majority of tumors stained for myoglobin (21 of 21 tumors), muscle-specific actin (21 of 21 tumors), and desmin (19 of 21 tumors). Focal or rare immunoreactivity for vimentin (six of 17 cases), alpha-smooth muscle actin (17 of 20 cases), S-100 protein (14 of 21 cases), and Leu-7 (10 of 20 cases) also was detected. Cytokeratin, epithelial membrane antigen, glial fibrillary acidic protein, and CD68 antigen (with KP1) were not found. The characteristic histology and immunophenotype distinguish ARM from other lesions with which it is frequently confused, including granular cell tumor, hibernoma, oncocytoma, and paraganglioma. The expression of alpha-smooth muscle actin has not been reported previously in ARM; its presence could reflect aberrant expression of smooth muscle actin in skeletal muscle or possibly be a recapitulation of early skeletal muscle embryogenesis.

Calcifying fibrous pseudotumor.

We report 10 cases of a distinctive benign fibrous lesion characterized by the presence of abundant hyalinized collagen with psammomatous or dystrophic calcifications and a lymphoplasmacytic infiltrate. The lesions were present from 2 months to 10 years before resection and ranged in size from 2.5 to 15 cm. They involved subcutaneous and deep soft tissues and, although relatively well-circumscribed, occasionally infiltrative borders or entrapped structures were seen on microscopic examination. The lesions were located in the extremities (three cases), trunk (two cases), scrotum (two cases), groin (one case), neck (one case), and axilla (one case). Both sexes were equally affected. The mean and median ages of the patients were 16.2 and 18.5 years, respectively (range, 1 to 33 years). All cases were initially managed by simple local excision. Follow-up ranging from 2 months to more than 10 years (median, 41.5 months) was available in six cases and revealed a local recurrence in one instance; this became clinically apparent about 7.5 years after the initial resection. Morphologic features and follow-up data suggest this may be a unique form of fibrous pseudotumor.

Ossifying fibromyxoid tumour (of soft parts) of the head and neck: a clinicopathological and immunohistochemical study of nine cases.

Ossifying fibromyxoid tumour (OFT) is a recently described, mesenchymal neoplasm originally defined as a borderline or low-grade malignant lesion. Prior reports of OFT characterize it as a slow growing lesion with a propensity to occur in both the upper and lower extremities. Most OFTs have occurred within the deep subcutis or skeletal muscle. We report nine cases which arose in the head and neck region. Six of the nine tumours were classified as ossifying variants of OFT while two were non-ossifying variants that lacked a discernable shell of lamellar bone. One tumour was classified as a malignant OFT. Seven lesions occurred in a subcutaneous site while two lesions occurred intraorally beneath the gingival and palatal mucosa. The OFTs occurred in six men and three women (age range of 29-75 years). The tumours had histological features compatible with previously described OFTs and consisted of lobulated nests of small, cytologically bland round cells (with the exception of one malignant OFT), with a myxoid to hyalinized stroma and were surrounded in part by dense fibrous connective tissue. Six cases had an incomplete rim of lamellar bone with occasional perpendicularly oriented spicules of bone. Five lesions were immunostained. S-100 protein, neuron specific enolase, and Leu-7 were found in three out of five tumours. Glial fibrillary acidic protein, smooth muscle actin (SMA), and muscle specific actin (MSA) were detected in two out of five lesions, although staining for SMA and MSA was weak in reactivity. Staining for vimentin was strongly positive in all five cases tested. The tumours were not reactive with antibodies directed against cytokeratin, epithelial membrane antigen or neurofilament protein. Follow-up information, available in eight cases, revealed multiple local recurrences in the one tumour believed to be a malignant OFT. The histogenesis of these tumours is uncertain, although the preponderance of evidence suggests a Schwann cell origin.

Elastofibroma: MR and CT appearance with radiologic-pathologic correlation.

OBJECTIVE: The purpose of our study was to determine the MR and CT appearances of elastofibroma and correlate the imaging features with the underlying pathologic findings. MATERIALS AND METHODS: We reviewed retrospectively the MR and CT findings in five cases of elastofibroma. All patients had a soft-tissue mass; one patient also complained of pain. The mean age of the patients was 71 years (range, 63-79 years). Four lesions occurred in the subscapular region, and one occurred in the thigh. In addition, we reviewed and compared the demographic data of 72 histologically proved cases for which we had archival data. RESULTS: Three of four lesions evaluated with spin-echo MR imaging were approximately isointense with skeletal muscle and contained areas with a signal intensity similar to that of fat; these corresponded to areas of dense collagen and interspersed fat, respectively. In the fourth case, the MR appearance was nonspecific. In one case, MR imaging with gadopentetate dimeglumine showed areas with and without enhancement. Three of four lesions evaluated with CT had variable margins, with tissue attenuation similar to that of the adjacent soft tissue as well as scattered areas of decreased attenuation, suggesting fat within the lesion. In one case, the lesion was well defined and relatively homogeneous with an attenuation less than that of skeletal muscle. CONCLUSION: The MR and CT features of elastofibroma are different from those of most other soft-tissue tumors, reflecting entrapped fat within a predominantly fibrous mass. Although these features are not pathognomonic, their presence in a subscapular lesion in an older patient suggests a presumptive diagnosis of elastofibroma.

Malignant peripheral nerve sheath tumors (malignant schwannomas) in children.

We studied the clinical and pathologic features of 78 malignant peripheral nerve sheath tumors in children less than or equal to 15 years of age. There were 42 boys and 36 girls, with a median age of 10 years. The majority of the tumors (42, or 54%) were central or axial in location; the rest were peripheral. Sixteen patients (21%) had a history of von Recklinghausen's disease. Fourteen (18%) had a malignant peripheral nerve sheath tumor arising in a nerve trunk or a neurofibroma and were unassociated with von Recklinghausen's disease. Patients typically presented with a painful mass of variable duration. Tumors ranged from 2 to 33 cm (median, 7.5 cm) and demonstrated a wide histologic spectrum that included spindled, epithelioid, and primitive neuroepithelial-like cells as well as heterologous elements (11). Immunohistochemical staining revealed S-100 protein in 28 of 50 cases (56%) as well as vimentin (13 of 21 cases, or 62%), Leu 7 (22 of 49 cases, or 45%), actin (eight of 20 cases, or 40%), and keratin (seven of 27 cases, or 26%). Survival status was known for 57 patients (73%). Kaplan-Meier estimates revealed a median survival of 45 months. Half of the patients had local recurrences at 12 months, and half had metastases at 24 months, most commonly to lungs, followed by lymph nodes, liver, bone, soft tissue, and brain. Age greater than or equal to 7 years, male sex, presence of von Recklinghausen's disease, central location, larger tumor size, and tumors with greater than or equal to 25% necrosis were found to be potentially significant adverse prognostic indicators by univariate analysis. Multivariate analysis revealed that larger tumor size, age greater than or equal to 7 years, tumor necrosis greater than or equal to 25%, and von Recklinghausen's disease to be independent adverse prognostic factors.

Atypical decubital fibroplasia. A distinctive fibroblastic pseudotumor occurring in debilitated patients.

We report 28 cases of atypical decubital fibroplasia, a distinctive pseudosarcomatous fibroblastic proliferation occurring primarily but not exclusively in physically debilitated or immobilized patients. The subjects included 16 women and 12 men ranging in age from 15 to 95 years. Peak incidence was in the 8th and 9th decades of life. Anatomic locations included the soft tissues overlying the shoulder (eight cases), posterior chest wall (five cases), sacrum (five cases), greater trochanter (four cases), buttock (two cases), thigh (two cases), and arm (two cases). Symptoms were due to a painless mass of 3 weeks' to 6 months' duration. Most lesions were ill-defined, focally myxoid masses that ranged from 1 to 8 cm. Histologically, they were situated in the deep subcutis and secondarily involved adjacent skeletal muscle (11 cases) and tendon (three cases). Extensive epidermal ulceration was typically absent. Microscopically, the lesions had a lobular configuration. They were characterized by zones of fibrinoid necrosis and a prominent myxoid stroma rimmed by ingrowing, ectatic, thin-walled vascular channels. All cases contained atypical, enlarged, degenerated fibroblasts with abundant basophilic cytoplasm, large hyperchromatic, smudged nuclei, and prominent nucleoli; these features resulted in a superficial resemblance to proliferative fasciitis. The enlarged, atypical fibroblasts stained diffusely and strongly for vimentin (15 of 15 cases) and focally for muscle-specific actin (10 of 15 cases), keratin (one of 15 cases), CD68 (10 of 15 cases), and CD34 (five of nine cases) antigens; none of the cases stained for desmin. A malignant diagnosis was considered in 43% of cases. Follow-up in 21 patients ranged from 2 to 78 months (median, 12 months). Two lesions recurred once, one recurred twice, and none metastasized; no deaths were attributable to the lesions. The clinical, histologic, and immunohistochemical features of atypical decubital fibroplasia indicate it is a unique type of pressure sore displaying degenerative and regenerative features distinct from decubitus ulcer. Its recognition by pathologists and clinicians in elderly and debilitated patients is important to avoid misdiagnosis as a sarcoma and to prevent or minimize the occurrence of decubital fibroplasia in progressively aging patient populations.

Juxta-articular myxoma: a clinical and pathologic study of 65 cases.

We describe 65 cases of juxta-articular myxoma (JAM) that occurred in the vicinity of large joints, possessed histologic features of a myxoma, and were frequently associated with cystic changes that resembled a ganglion cyst. The vast majority of cases (57, 88%) occurred in the region of the knee; a minority involved the shoulder (three cases), elbow (three), ankle (one), and hip (one) regions. Patients' ages ranged from 16 to 83 years (median, 43 years; mean, 44 years) and nearly three fourths of the patients (72%) were male. Thirty-seven lesions presented as a swelling or mass, 21 were associated with pain or tenderness, and sizes ranged from 0.6 to 12 cm (median, 3.5 cm; mean, 3.8 cm). Duration of symptoms was highly variable, spanning from 1 week to 18 years. Fourteen JAMs were intimately associated with the meniscus and five of these had a concomitant tear; in five other cases JAM was an incidental finding at the time of total knee or hip arthroplasty for severe osteoarthritis. Of 29 cases with follow-up, 10 (34%) recurred: five recurred once, two recurred twice, two recurred three times, and one recurred four times. While the majority of JAMs were correctly diagnosed as benign, a sarcoma was seriously considered or diagnosed in 15 (23%) cases.

Proliferative fasciitis and myositis of childhood.

Eleven cases of proliferative fasciitis and myositis in children, ages 2.5 months to 13 years, are presented. Eight lesions averaging 2.3 cm in size occurred in the extremities, two in the head and neck region and one on the chest wall. Like proliferative fasciitis and myositis in adults, these lesions consisted of admixtures of large polygonal to spindled, ganglion-cell-like fibroblasts with vesicular nuclei and prominent inclusion-like nucleoli. Seven of 11 lesions were initially diagnosed as sarcomas, most commonly rhabdomyosarcoma. Four patients were treated by wide excision (three with regional lymphadenectomy), three received chemotherapy, and one was given radiation therapy. There were some histologic differences from adult-type proliferative fasciitis and myositis. The childhood lesions were generally well circumscribed, lobulated, extremely cellular with less collagen production, and often associated with acute inflammation and microscopic foci of necrosis. Immunohistochemical comparison with adult proliferative fasciitis and myositis showed similar immuneprofiles; the ganglion-like cells stained for vimentin and actin and focally with KP1, suggesting myofibroblastic and histiocytic features. None of the lesions stained for keratin, desmin, or S-100 protein. Ultrastructural examination of two cases revealed cells with a constellation of fibroblastic, myofibroblastic, and histiocytic features. Follow-up of seven patients, averaging 58 months from diagnosis, confirmed that all are alive and well. Recognition of this cellular variant of proliferative fasciitis and myositis is important to prevent misdiagnosis as a sarcoma and unnecessary, excessive therapy.

Rosai-Dorfman disease of soft tissue.

Whereas Rosai-Dorfman disease (RDD) or sinus histiocytosis with massive lymphadenopathy is well described in lymph nodes and other organs, it is frequently not recognized in soft tissue. We studied the clinical and histologic features of 23 previously unreported soft tissue lesions from 17 patients (13 females, 4 males) who were 24 to 66 years of age (mean, 46 years). These lesions involved the extremities (12, 52%), trunk (6, 26%), head and neck (3, 13%), and the retroperitoneum (2, 9%). Associated lymph node involvement was present in four cases; most patients were asymptomatic. RDD of soft tissue had more subtle histologic features than its lymph node counterpart. Emperipolesis was less conspicuous and proliferating histiocytes were frequently spindled, associated with collagen deposition, and arranged in a vague storiform pattern with scattered lymphoplasmacytic aggregates. These features led to a variety of diagnoses, including benign inflammatory and fibrohistiocytic lesions (13 cases) as well as lymphoma and malignant fibrous histiocytoma (three cases). RDD was correctly diagnosed in only one case. Diagnosis was confirmed in 16 of 18 lesions by detection of S-100 protein and histiocytic markers KP1 (12 of 13) and lysozyme (eight of 11) in the characteristic histiocytes. Recognition that RDD of soft tissue occurs in an older patient population than does nodal RDD and that it mimics fibrous and inflammatory lesions of soft tissue is important.

Myositis ossificans: MR appearance with radiologic-pathologic correlation.

We reviewed retrospectively the MR images of eight histologically proved cases of myositis ossificans and correlated the MR appearance with the histologic findings, as well as with other radiologic studies. Patients with available MR images were chosen from a group of 326 cases in our radiologic archives of histologically proved and radiologically correlated myositis ossificans. In addition to MR images, all patients had plain radiographs, six had CT scans, and two had arteriograms. On T2-weighted spin-echo MR, the lesions were relatively well defined and inhomogeneous and had intermediate to high signal intensity. The latter corresponded to a central proliferating core of fibroblasts and myofibroblasts with a myxoid stroma resembling nodular fasciitis, rimmed by osteoblasts with bone production. Edema surrounded lesions less than a few months old. T1-weighted images of early lesions were normal or showed evidence of a mass by displacement of fat planes. Hemorrhage and fluid-fluid levels were seen in one lesion of intermediate duration. Mature lesions tended to be well defined with inhomogeneous signal intensity, similar to that of fat, representing areas of fat situated between bone trabeculae within the lesion. We present the MR appearance of myositis ossificans and correlate it with other radiologic studies and the histologic findings. The varying appearance of myositis ossificans relates to the histologic changes that occur as the disorder progresses. Knowledge of the MR appearance of myositis ossificans is important in that the lesion has many of the MR imaging characteristics frequently associated with malignancy.

Inflammatory fibrosarcoma of the mesentery and retroperitoneum. A tumor closely simulating inflammatory pseudotumor.

We report 38 cases of inflammatory fibrosarcoma occurring in 23 females and 15 males, 2 months to 74 years of age (median, 8.5 years; mean, 15 years) with symptoms of abdominal pain (17 cases), anemia (21 cases), fever (14 cases), mass (16 cases), and gastrointestinal obstruction (7 cases). Primary tumor sites included mesentery and retroperitoneum (31 cases), omentum (two cases), mediastinum (two cases), liver (one case), diaphragm (one case), and abdominal wall (one case). Sizes ranged from 2.4 cm to 20 cm (mean, 9.6 cm). Follow-up data in 27 cases revealed local recurrences in 10 patients, with multiple local recurrences in three and histologically proven distant metastases to lung (two cases) and brain (one case). Five patients died from their disease (median, 20 months). All tumors, including metastases, consisted of fibroblasts, myofibroblasts, and plasma cells, with variable degrees of fibrosis and calcification. Immunostains indicate myofibroblastic differentiation; 18 of 20 (90%) stained for actin, 15 of 18 (83%) for vimentin, and 10 of 13 (77%) for keratin (primarily in a submesothelial location). Ultrastructural studies also disclosed myofibroblastic features. The locally aggressive, recurrent nature of these neoplasms, as well as the occurrence of metastases and tumor deaths, indicate that they are potentially malignant neoplasms that we believe are better classified as inflammatory fibrosarcomas, not as cellular inflammatory pseudotumors.

A histomorphologic and immunohistochemical study of chordoma in twenty ferrets (Mustela putorius furo).

The histomorphologic and immunohistochemical features of chordoma in 20 ferrets were evaluated. The mean age was 3.4 years, and, in the cases for which sex was known, females (n = 10) outnumbered males (n = 5) two to one. All 20 tumors occurred on the tip of the tail. Nineteen of 20 tumors (95%) were composed of three tissue components, often arranged concentrically with lobules of physaliferous cells at the periphery, trabecular bone in the center, and cartilage in between. The bone often contained marrow and hematopoietic cells. One tumor lacked chondromatous or osseous tissue. Immunohistochemical results were consistent with previous studies of chordoma. All 20 tumors (100%) were positive for keratin and vimentin intermediate filaments; 15 (75%) were positive for S-100 protein; and 17 (85%) were positive for neuron specific enolase. This neoplasm shares morphologic and immunohistochemical features with "classic," as well as chondroid chordoma, of human beings, making it a potential animal model.