EXTRAPULMONARY INFLAMMATORY MYOFIBROBLASTIC TUMOR - A CLINICAL AND PATHOLOGICAL SURVEY

Inflammatory myofibroblastic tumor (IMT) or inflammatory pseudotumor w as initially recognized in the lung, and somewhat later, a similar-app earing pathological process was reported in the river. Presently, this tumor has been described in virtually all major organs and extrapulmo nary sites with a few exceptions. It was thought initially that the IM T was nonneoplastic and represented an aberrant inflammatory response despite its gross and microscopic features of a spindle cell neoplasm. The inflammatory hypothesis about the pathogenesis has been more read ily accommodated in the lung than in the extrapulmonary sites of invol vement. Some cases, however, were accompanied by the constitutional sy mptoms and signs of an inflammatory process, which resolved in most ca ses after surgical resection. There were some pathological aspects of the IMT that seemingly contradicted its purely inflammatory nature, in cluding its potential for local recurrence; development of multifocal, noncontiguous tumors; infiltrative local growth; vascular invasion; a nd malignant transformation, These pathological features seemed to sup port the hypothesis that the IMT is a neoplastic process, which has be en augmented by reports that these tumors have clonal characteristics. Other studies have suggested that IMTs of the river and spleen are as sociated with the Epstein-Barr virus. From the diagnostic perspective, there are several potential difficulties that the pathologist may enc ounter in the examination of one of these tumors. Just as it was true 60 years ago, the potential for a pathological diagnosis of one or ano ther type of spindle cell sarcoma has not diminished with time. Becaus e these tumors have a predilection for children, embryonal rhabdomyosa rcoma is another diagnostic temptation when an IMT presents in the bla dder or other hollow viscus. The IMT should probably be regarded as a soft tissue-mesenchymal tumor with an indeterminant or tow malignant p otential, which is a somewhat indefinite but realistic prognostic cate gory. Copyright (C) 1998 by W.B. Saunders Company.