[1042] Detection of ALK Gene Rearrangements Aids in the Diagnosis of Inflammatory Myofibroblastic Tumor of the Uterus.

Neil E Fuehrer, Debra A Bell. Mayo Clinic, Rochester, MN

Background: Inflammatory myofibroblastic tumor (IMT) is a predominantly benign spindle cell mesenchymal neoplasm that occurs very rarely in the uterus and may be confused with other spindle cell lesions in the gynecologic tract, particularly leiomyosarcoma. A variable staining pattern of many IMTs with keratins and smooth muscle markers contributes diagnostic difficulties.
Design: To better define the histologic features of uterine inflammatory myofibroblastic tumors and to investigate the utility of detection of ALK-1 protein expression and ALK gene rearrangements in the diagnosis of uterine IMT we reviewed four cases of atypical inflammatory myofibroblastic tumors seen in our consultation practice. Immunostains for desmin, SMactin, CD-10, keratins and ALK-1 were performed on all cases. FISH detection for ALK gene rearrangements was performed in the 3 cases in which tissue was available.
Results: The specimen sites for the IMTs included uterus (2 cases), cervix and cervical polyp and age range was from 26 years to 48 years. Histologic atypia ranged from bland spindle cells to moderate cytologic atypia with pleomorphic vesicular nuclei and prominent nucleoli. All had low mitotic activity, scattered mixed inflammatory infiltrate, and lacked true tumor necrosis. All contained distinct areas of spindle cells embedded in a prominent myxoid background. Immunohistochemical staining varied in regards to CD10, keratin, and smooth muscle markers, however ALK-1 (anaplastic lymphoma kinase 1) staining was consistently positive with a cytoplasmic staining pattern. FISH studies detected ALK gene rearrangements in the three cases analyzed.
Conclusions: IMT is a very rare tumor in the uterus, but should always be included in the differential of malignant myxoid lesions of the uterus such as the myxoid variants of leiomyosarcoma and endometrial stromal sarcoma. If a myxoid background is appreciated in a spindle cell lesion of the uterus, especially if inflammatory cells are present, ALK-1 immunohistochemical staining and FISH studies for ALK gene rearrangements may aid in distinguishing largely benign IMTs from their malignant mimics.
Category: Gynecologic & Obstetrics

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 193, Wednesday Afternoon


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