ANGIOMATOID FEATURES IN FIBROHISTIOCYTIC SARCOMAS - IMMUNOHISTOCHEMICAL, ULTRASTRUCTURAL, AND CLINICAL DISTINCTION FROM VASCULAR NEOPLASMS

The typical example of malignant fibrous histiocytoma (MFH) or dermato fibrosarcoma protruberans (DFSP) does not require ancillary studies fo r diagnosis. However, hemorrhage with cystic change consisting of bloo d-filled spaces may closely mimic a vascular neoplasm. Eight fibrohist iocytic sarcomas exhibiting these angiomatoid features, initially mist aken for vascular neoplasms, were identified from personal consultatio n files and review of 157 consecutive sarcomas (1985 through 1993) at the University of California-(Davis) Medical Center. They included fiv e MFH giant-cell-type sarcomas, two MFH angiomatoid-type sarcomas, and one DFSP. Immunohistochemical analysis of paraffin-embedded material showed vimentin diffuse positive, CD68 (KP-1) diffuse positive, and fa ctor VIII negative in al eight sarcomas; actin HHF-45 focal positive i n six, diffuse positive in one, and negative in one sarcoma; desmin fo cal positive in two and negative in six sarcomas; and S100 protein, cy tokeratin AE1:AD3 cytokeratin 10.11, and EMA negative in all eight sar comas. Electron microscopy of three tumors exhibited neoplastic cells with fibroblastic, myofibroblastic, and histiocytic features. Weibel-P alade bodies or neolumens diagnostic of vascular differentiation were absent. The clinical characteristics and behavior of these sarcomas re flect entities in the spectrum of fibrohistiocytic lineage (MFH subtyp es and DFSP) rather than vascular neoplasms. Patients with deep, targe , giant-cell-type MFHs did poorly (two of four patients died from dise ase at 8 and 25 months). Both patients with angiomatoid MFHs showed lo cal recurrences from large incompletely excised head and neck lesions. One died of disease at 21 months and the other is free of disease 12 months following excision of a local metastasis to the opposite side o f the neck. The patient with DFSP had an 18-cm locally recurrent scalp tumor that extended into bone. Immunohistochemical and ultrastructura l confirmation of fibroblastic, myofibroblastic, and histiocytic linea ge and exclusion of vascular differentiation help to establish the cor rect diagnosis in these fibrohistiocytic sarcomas with angiomatoid fea tures. The clinicopathologic features of these eight cases reaffirm th e practical utility of MFH and DFSP as diagnostic entities in the spec trum of fibrohistiocytic sarcomas.