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14 April 2005 - Case #3

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Case #3

Clinical history:
This is a recurrent soft tissue tumor from the ankle region of a 90 year old woman. This is the second recurrence of this mass within an 18 month period. The previous diagnoses were fibroma of tendon sheath and recurrent fibroma. She recently underwent wide local reexcision.

Gross description:
The mass was 4.5 cm, well demarcated, white-tan and firm, without areas of necrosis or hemorrhage.

Microscopic description:
The tumor is composed of cord-like clusters of ovoid to slightly rounded cells with scant faintly eosinophilic cytoplasm, hyperchromatic nuclei and minimal pleomorphism. Tumor cells are surrounded by a dense collagenous stroma. No mitotic figures are present in this field.

Microscopic images:


Positive stains:
Vimentin

Negative stains:
Keratin, S100, desmin, actin

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Diagnosis: Sclerosing epithelioid fibrosarcoma

Discussion:
In 1995, Meis-Kindblom and colleagues from the AFIP reported an uncommon, peculiar sclerosing epithelioid variant of fibrosarcoma that simulated an infiltrating carcinoma (AJSP 1995;19:979). These tumors occurred primarily in the deep musculature, most often of the lower extremities and limb girdles and trunk and were frequently associated with adjacent fascia or bony periosteum. Median patient age was 45 years, with a wide age range (14 - 87 years) and no definite gender preference. Tumors were large, with a median size of 7 cm, gray-white and firm. The lesions were characterized by a proliferation of uniform nests and cords of small, round / oval epithelioid cells with scant, often clear cytoplasm. All cases had prominent hyaline sclerosis. Occasional features were osteoid, cartilage, myxoid zones with cyst formation or foci of classic fibrosarcoma. There were no / rare mitotic figures.

The tumor cells were immunoreactive for vimentin, p53 and BCL2 in almost all cases, often stained with EMA and occasionally stained with S100, NSE, AE1 / AE3 and CAM 5.2. They were negative for LCA (CD45), CD68, HMB45, desmin and alpha smooth muscle actin. Proliferative activity, as measured by Ki67, was low (≤ 5%). Ultrastructurally, the tumor cells had features of fibroblasts. With a median follow up of 11 years, there were local recurrences in 53% and metastases in 43% to lung, skeleton, chest wall / pleura, pericardium and brain. Death due to disease occurred in 25%.

These findings were confirmed in 1991 by Antonescu and colleagues from Memorial Sloan-Kettering, who also reported bone invasion and tumor necrosis (AJSP 2001;25:699). They found local recurrence in 50% but distant metastases in 86%, with death due to disease in 57%. Thus, although this tumor has a relatively bland appearance, it behaves as a fully malignant sarcoma.

The differential diagnosis of sclerosing epithelioid fibrosarcoma includes other fibrosing type fibrosarcomas, namely low grade fibromyxoid sarcoma and hyalinizing spindle cell tumor with giant rosettes. Other entities to consider are monophasic synovial sarcoma, epithelioid sarcoma, epithelioid leiomyosarcoma, epithelioid MPNST, melanoma, carcinoma and fibroma of tendon sheath.

Low grade fibromyxoid sarcoma typically has a monotonous hypocellularity, with alternating myxoid and collagenous stroma, sometimes blending with areas of increased cellularity. Hyalinizing spindle cell tumor with giant rosettes has distinct hypercellular regions in which tumor cells are arranged as palisading granulomas with giant rosettes. Both have only small foci of epithelioid cells. Monophasic synovial sarcoma may resemble the hypercellular areas of sclerosing epithelioid fibrosarcoma but lacks large areas of sclerotic collagen, as do the other epithelioid tumors. Sclerosing epithelioid fibrosarcoma may resemble fibroma of tendon sheath or a benign lesion if the cellular areas are not biopsied or are overlooked. (J Clin Path 2004;57:90)

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