Malignant monomorphic histiocytoma in children

Four cases of malignant histiocytoma in children are reported. Malignant histiocytoma is defined as a histologic variant of fibrohistiocytoma, characterized by a histologic absence of a fibroblastic component, and a predominant proliferation of malignant histiocytes with an epithelial-like appearance. However, the ultrastructural study of one case also revealed the presence of fibroblasts. Thus, an authentically pure form of malignant histiocytoma does not exist. Nonetheless, it is important to emphasize the histologic distinctions between malignant histiocytoma and malignant fibrohistiocytoma and to emphasize the possible differences in their biologic behavior.