Angiomatoid malignant fibrous histiocytoma: a distinct fibrohistiocytic tumor of children and young adults simulating a vascular neoplasm.

This article describes 41 examples of an unusual fibrohistiocytic sarcoma which occurred primarily in the extremities of young individuals between the ages of 5 and 25 years (median 13 years). It manifested as a nodular subcutaneous growth that seldom caused tenderness or pain, and clinically was often mistaken for a hematoma or a hemangioma. Grossly, the tumor presented as a circumscribed, multinodular or multicystic, hemorrhagic mass that ranged in size from 0.7 to 10 cm (median 2.5 cm). On microscopic examination, it consisted principally of 1) solid arrays or nests of fibroblast- and histiocyte-like cells, not infrequently containing varying amounts of intracellular hemosiderin or lipid, 2) focal areas of hemorrhage or hemorrhagic cyst-like spaces, sometimes occupying the major portion of the tumor, and 3) aggregates of chronic inflammatory cells, chiefly lymphocytes and plasmacytes, a feature that caused confusion with a lymph node metastasis in several cases. Follow-up information, available in 24 patients, revealed a variable clinical course. Twenty-one patients were alive, 11 with recurrence (including one with 9 recurrences in a 21-year period) one with recurrence and metastasis and one with metastasis. Three patients had died of metastasis 1, 3, and 13 years respectively, after the initial surgical therapy. The exact histogenesis is still obscure. Most likely it is a tumor of fibroblast- and histiocyte-like cells, akin to malignant fibrous histiocytoma, but different in its age incidence, microscopic appearance and behavior.