[76] Low-Grade Fibromyxoid Sarcoma. A Clinicopathologic Study

HL Evans. UT M.D. Anderson Cancer Center, Houston, TX

Background: Previous studies of low-grade fibromyxoid sarcoma have had too few cases, too little follow-up, or both to provide a comprehensive pathologic and clinical picture of the tumor.
Design: Cases of low-grade fibromyxoid sarcoma in our files were reviewed. They were included if there was adequate histologic material and clinical information with at least 5 years follow-up.
Results: Thirty-three cases met the study criteria. The patients were 6 to 52 years old (median 29 years); 19 were male and 14 female. The most common tumor locations were the shoulder area (5), thigh (5), and inguinal area (4). Tumor size varied from 1.5 cm to 16 cm (median 9.4 cm) where it was known. The typical histologic findings were contrasting fibrous and myxoid areas, moderate to low cellularity, bland-appearing spindle cells with no or slight nuclear pleomorphism and rare mitotic figures, and a swirling, whorled growth pattern. Prominent vascularity in myxoid areas and perivascular hypercellularity were fairly common, whereas larger hypercellular zones were sometimes seen in primary tumors but were more frequent in recurrences (local) and metastases. Hypercellular regions sometimes had round rather than spindle cells and a somewhat increased mitotic rate. Features less often observed included focal moderate nuclear pleomorphism (usually in recurrences), areas with a storiform, straight, fascicular or diffuse cell arrangement, thick collagen bundles, and osseous metaplasia. Pericollagenous rosettes were present in 6 cases but not in all specimens from these. One patient had a recurrence with features of sclerosing epithelioid fibrosarcoma, whereas 2 had dedifferentiated recurrences with anaplastic predominantly round cells and numerous mitotic figures. Thirteen patients died of tumor after 3 (tumor became dedifferentiated) to 31½ years (median 11 years). Twenty patients were alive at latest follow-up of 5 to 67 years (median 12 years), 6 with tumor and 14 without. Twenty-one patients had recurrence after intervals of up to 15 years (median 3½ years), and 15 had metastases (mostly in lungs and pleura) after periods of up to 45 years (median 5 years). Except for dedifferentiation, which led to short survival after it occurred, histologic differences were not related to tumor behavior or patient survival. The 4 patients whose neoplasms measured less than 3.5 cm were all tumor-free at latest follow-up.
Conclusions: Low-grade fibromyxoid sarcoma has a range of histologic features beyond the typical pattern, but these differences do not relate to tumor behavior or patient survival. Small tumor size may be a favorable prognostic factor.
Category: Bone & Soft Tissue

Monday, March 22, 2010 11:45 AM

Platform Session: Section F, Monday Morning

 

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