[Uterine inflammatory myofibroblastic tumor: a clinicopathological and molecular genetic analysis of eight cases].
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Objective: To investigate the clinicopathological and molecular genetic characteristics of uterine inflammatory myofibroblastic tumor (UIMT). Methods: A retrospective analysis was conducted on 8 patients diagnosed with UIMT at Changzhou First People's Hospital, Changzhou Wujin Hospital of Traditional Chinese Medicine, Changzhou Second People's Hospital, and Changzhou Maternal and Child Health Care Hospital from January 2018 to July 2025, including 6 cases of non-aggressive UIMT, 1 case of aggressive UIMT and 1 case of epithelioid inflammatory myofibroblastic sarcoma (EIMS). The clinicopathological features, molecular genetic characteristics, treatment and prognosis were summarized. Results: The patient's age was 44.5(38.5, 46.0) years old, and the tumor size was 6.35(5.05, 8.70) cm. Among the cases, one tumor was located submucosally within the uterus, four were within the uterine muscular wall, and three were subserosa. The tumors exhibited heterogeneous morphological features: non-aggressive UIMT displayed either a mucinous pattern with sparse cellularity or a dense fascicular pattern (similar to smooth muscle), with well-defined tumor margins or invasive growth; UIMT with aggressive behavior showed invasive growth, with greater cellular atypia, more mitotic figures, and necrosis. One EIMS showed invasive growth, mainly composed of epithelioid cells with focal spindle cell morphology, significant cellular atypia, active mitotic figures, and a small amount of lymphocyte and plasma cell infiltration between the epithelioid cells. Fluorescence in situ hybridization (FISH) testing detected ALK rearrangement in all eight cases. RNA next generation sequencing (NGS) indicated that all tumors were driven by ALK rearrangement. Among these tumors, EIMS harbored a novel fusion gene, KANK2::ALK. DNA NGS demonstrated that UIMT with aggressive behavior and EIMS harbored more pathogenic gene alterations, including mutations in TP53 and ATM, as well as amplification of the CCNE1 gene. Except for EIMS, immunohistochemical analysis revealed positive expression of ALK protein in 7 cases of UIMT. Immunohistochemistry also showed abnormal expression of p16 or p53 protein in EIMS and one case of UIMT with aggressive behavior. All patients underwent surgical treatment. The follow-up period ranged from 4 to 84 months. One patient with aggressive behavior of UIMT developed liver and lung metastases 4 months after the surgery. The patient was treated with the oral targeted drug crizotinib and died of multiple organ failure 18 months after surgery. Conclusions: UIMT is a morphologically heterogeneous neoplasm, and its biological behavior can vary from benign to highly aggressive. This type of tumor is mainly driven by ALK gene rearrangement. UIMT and EIMS that exhibit aggressive behavior typically possess a greater number of genetic alterations. The abnormal expression of p53 or p16 protein, when combined with clinicopathological parameters, can serve as indicators for predicting the adverse biological behavior of tumors.