Image Description
Microscopic Features: The pleomorphic areas have haphazardly distributed plump fibroblastic and histiocyte-like cells with markedly atypical, bizarre-shaped hyperchromatic nuclei. Nuclear pleomorphism and mitotic activity are more pronounced than storiform areas. Multinucleated giant cells with abundant eosinophilic cytoplasm are also present. They resemble rhabdomyoblasts but are negative for skeletal muscle markers (myogenin, MyoD1, desmin). Some cases have a predominant fascicular growth pattern resembling fibrosarcoma.