What is a malignant fibrous histiocytoma (MFH)?

MFH is a malignant soft tissue tumor arising in the deep soft tissue. It is thought by several authors not to represent a diagnostic entity, but a common, final pathway of many tumors, as its features are shared by a variety of poorly differentiated malignant neoplasms. The term MFH is now reserved for the small group of truly undifferentiated pleomorphic sarcomas. The histogenesis has been a cause of an ongoing debate, but it is now accepted that the histiocyte is most likely not the cell of origin of the tumor. More recent studies suggest that MFH is a sarcoma of a poorly defined mesenchymal cell, which may differentiate along histiocytic and fibrocytic lines. The term MFH is being substituted by pleomorphic sarcoma. Histologically, the tumor demonstrates a variable appearance with five subtypes: pleomorphic-storiform, myxoid (also called myxofibrosarcoma), giant cell, angiomatoid, and inflammatory. The histologic diagnosis is one of exclusion based on the histologic appearance and special stains, because these histologic patterns may be mimicked by other soft tissue tumors.

Al-Agha OM, Igbokwe AA: Malignant fibrous histiocytoma: between the past and the present, Arch Pathol Lab Med 132:1030–1035, 2008.