Malignant fibrous histiocytoma. History, histology, histogenesis.

At the XVI. International Congress of the International Academy of Pathology (Vienna, 1986), a session was dedicated to the classification of soft tissue tumors. At this occasion a critical review of malignant fibrous histiocytoma (MFH) was presented. A) The history of MFH revealed that this tumor had been known for many years under a variety of names. Moreover, MFH apparently had frequently been misinterpreted as other tumor types, as for instance rhabdomyosarcoma. Today, there is a discrepancy between the high incidence of MFH among soft tissue sarcomas and its underrepresentation in some widely used tumor classifications. B) The histological appearance may be fully developed and typical for MFH. However, it also may be merely compatible with MFH in less typical tumor areas. Regional differences in morphological appearance may be pronounced. Differential diagnosis can be helped by histochemical methods. C) Histochemical methods--among others--also help to shed light on the histogenesis. More recent findings point to MFH, as a tumor of fibroblasts rather than histiocytes with similarities to loose areolar connective tissue. Although MFH-like areas may occur focally within a variety of different tumors, there remains a large group of sarcomas which do not display any signs of further differentiation even after careful work-up. In these cases the application of the term MFH, as it is understood today, appears to be justified.