Fibrosarcoma

High-grade fibrosarcoma showing more pleomorphic nuclei, frequent mitoses, and less collagen. Fibrosarcomas are vimentin pos, keratin neg (helpful for distinction from monophasic synovial sarcoma), S-100 neg (distinction from desmoplastic melanoma). SMA and/or MSA may be focally positive due to myofibroblastic differentiation. Radical excision reduces recurrence risk and improves survival rates.