Angiomatoid malignant fibrous histiocytoma. A follow-up study of 108 cases with evaluation of possible histologic predictors of outcome.

Described by Enzinger in 1979, angiomatoid malignant fibrous histiocytoma is a distinctive tumor of adolescence and early adult life characterized by sheets of relatively bland rounded or spindled cells separated by areas of cystic hemorrhage and surrounded by a prominent inflammatory infiltrate and often a fibrous pseudocapsule. On the basis of the original 41 cases, the tumor has been considered a low-grade malignancy. We are reporting the clinicopathologic findings and follow-up information of 108 new cases of angiomatoid malignant fibrous histiocytoma to determine the long-term behavior of this tumor and whether various histologic features (atypia, mitoses, infiltrative borders, and inflammatory infiltrate) are useful in predicting outcome. Follow-up information was obtained in 94 (87%) cases. Local recurrences developed in 11 patients (12%), all of whom were cured by re-excision. The initial excision in all patients developing local recurrence appeared to be incomplete. Local recurrence was statistically associated with irregular tumor border and head and neck location. Five patients developed metastases. Four had only local metastases, which responded to surgery, whereas the fifth patient developed presumed pulmonary and cerebral metastases and died. The development of both local and distant metastases was correlated with invasion into the deep fascia or muscle but not to various histologic parameters such as mitotic rate and pleomorphism. We conclude that angiomatoid malignant fibrous histiocytoma is intrinsically a low-grade tumor, and assessment of various histologic parameters or grading provides little or no additional prognostic information. Because death from disease occurred in only one patient (1%) in our series, it seems reasonable to reclassify angiomatoid malignant fibrous histiocytoma with fibrohistiocytic tumors of intermediate malignancy rather than with the conventional malignant fibrous histocytoma, the majority of which are high-grade sarcomas.