374 Uterine Tumor Resembling Ovarian Sex Cord Tumor Mimicking High-Grade Endometrial Neoplasm: A Case Report

Abstract Introduction/Objective Uterine tumors resembling ovarian sex cord tumors (UTROSCTs) are rare neoplasms with varied histological patterns, often posing diagnostic challenges due to their resemblance to other uterine malignancies, particularly high-grade endometrial carcinomas. Methods/Case Report A 60-year-old female presented with abnormal uterine bleeding (AUB). Imaging revealed a large soft glistening tan polypoid lesion that attaches in the posterior fundus (4.5 cm) within the endometrial cavity. Results An endometrial biopsy showed predominantly short fascicles, moderately atypical spindle cells, and frequent mitoses. Immunohistochemistry demonstrated Desmin patchy positive, ER, vimentin and CK8/18 positive, CD10, EMA, CK7, Claudin-4 negative, P53 wildtype, P16 patch positive. The differentials include high grade endometrial stromal sarcoma, leiomyosarcoma, undifferentiated/dedifferentiated carcinoma, carcinosarcoma among others. Following hysterectomy specimen reveal sparse primitive tubules and vague cords architecture, which was particularly predominantly at the tumor-myometrial interface. Additional immunohistochemistry shows strong positivity for sex cord markers including calretinin, inhibin, and foxl2, with focal expression of epithelial markers. Therefore, the final diagnosis of uterine tumor resembling ovarian sex cord tumor (UTROSCT) was rendered based on morphology and immunophenotypic profile. Conclusion UTROSCTs are thought to arise from a pluripotent mesenchymal, endometrial stromal, or displaced ovarian sex cord cell. They typically behave in a benign fashion; however, they should ultimately be considered a tumor of low malignant potential because they may recur. However, no definitive prognostic morphological features have been identified.