INFLAMMATORY MYOFIBROBLASTIC TUMOR, INFLAMMATORY FIBROSARCOMA, AND RELATED LESIONS - AN HISTORICAL REVIEW WITH DIFFERENTIAL DIAGNOSTIC CONSIDERATIONS

The concept of the inflammatory myofibroblastic tumor (IMT) has evolve d from an already perplexing pathological process, the inflammatory ps eudotumor, which was initially recognized in the lung and regarded as a pseudoneoplasm, although its histological features resembled a spind le cell sarcoma. Despite the pathological findings and their apparent prognostic implications, most affected individuals regardless of the p rimary site have had favorable clinical outcomes. The designation of i nflammatory pseudotumor came to be widely accepted, although these les ions were clearly tumors or masses that may or may not have been pseud oneoplasms. An aberrant or exaggerated response to tissue injury witho ut an established cause has generally been favored as the pathogenesis of the inflammatory pseudotumor or IMT. Once the myofibroblast was id entified and its function in tissue repair was established, this cell type was found in a variety of soft tissue lesions from nodular fascii tis to malignant fibrous histiocytoma. The myofibroblast was eventuall y recognized as the principal cell type in the inflammatory pseudotumo r, which provided the opportunity to redesignate this tumor as IMT. So me of the clinical and pathological aspects of the IMT began to sugges t the possibility that these lesions are more similar to neoplasms tha n a postinflammatory process. Another step in the evolution of the inf lammatory pseudotumor and IMT occurred with the report of a mesenteric or retroperitoneal tumor with similar pathological features to the la tter tumors but with more aggressive behavior to warrant an interpreta tion of malignancy as an inflammatory fibrosarcoma. The IMT and inflam matory fibrosarcoma appear to have many overlapping clinical and patho logical features. These tumors are histogenetically related, and if th ey are separate entities, they are differentiated more by degrees than absolutes. The therapeutic approach to these tumors should relay prim arily on surgical resection, Studies in the future may possibly resolv e the question whether the IMT and inflammatory fibrosarcoma are synon ymous or closely related entities. Copyright (C) 1998 by W.B. Saunders Company.