Uterine inflammatory myofibroblastic tumor.

Inflammatory myofibroblastic tumor (IMT) is recognized as a true neoplasm of unknown etiology, but its pathogenesis is related to abnormalities in the ALK gene. This is an uncommon tumor with a wide anatomic distribution and often constitutes a challenging diagnosis owing to its histological similarities with other tumors. Uterine IMTs are rare and their detailed characteristics should be described based on case reports and small case series. Thus, we performed a comprehensive review of the literature showing that uterine IMTs show a wide range of age at diagnosis (median, 39 years), and a symptomatology similar to that of common leiomyomas, only rarely presenting with inflammatory manifestations. IMTs represent 0.1% of "leiomyomas," an estimate that increases to 10% for pregnant women and to 14% for the smooth muscle tumors of uncertain malignant potential (STUMP) category of tumors, implying that tumors excised during pregnancy, STUMPs, and leiomyosarcomas should be systematically screened with ALK immunohistochemistry, as this is a targetable abnormality. Most reported cases are ALK-positive; the fusion partners vary, but in pregnancy-associated tumors, TIMP3 prevails. Almost 25% of the patients will show an aggressive course, and this is associated with older age, non-pregnancy-associated tumors, larger tumors, infiltrative tumor border, absence of abundant inflammation, atypia, important mitotic activity, and necrosis.