[Clinical and molecular pathological features of uterine inflammatory myofibroblastic tumor]

Objective: To evaluate the clinical and molecular pathologic features of uterine inflammatory myofibroblastic tumor (UIMT). Methods: Six UIMT cases collected at Department of Pathology, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University from 2019 to 2020. They were analyzed for their general characteristics and clinicopathologic features. ALK rearrangements were detected by fluorescence in situ hybridization. Results: The age of the six patients ranged from 14 to 65 years, the tumors ranged in size from 2.5 to 6.0 cm. The masses were intramural or submucosal in location. Most of them (4/6) were white with yellow foci, and two (2/6) were white with tan foci. Other features noted included a soft or firm appearance. The fasciitis-like pattern of UIMT had myxoid stroma around the spindle cells and inflammatory cells. The ganglion-like pattern showed either fascicular or storiform architecture with diffuse growth. Nuclear atypia was mild or moderate. Mitoses ranged from 2 to 4 per 10 high-power fields. Five tumors were ALK-positive with granular cytoplasmic staining by immunohistochemistry. ALK rearrangements were detected in five cases but was absent in one case. Conclusions: UIMT is an intermediate grade soft tissue tumor, a minority may present with extrauterine spread and/or recurrence. The tumors are composed of spindled cells. The main differentials include smooth muscle tumors and endometrial stromal tumors and their morphology may overlap with that of UIMT. Immunohistochemical positivity for ALK or FISH testing for ALK rearrangements can help in the diagnosis.