Unexpected Uterine Leiomyosarcoma After Hysterectomy for Presumed Leiomyoma: A Case Report

Background: Uterine leiomyosarcoma is a rare malignant smooth muscle tumor that may remain unsuspected until definitive histopathological examination. Objectives: To describe diagnostic discordance between benign preoperative and gross impressions and malignant microscopic findings in uterine leiomyosarcoma. Methods: This case report retrospectively describes clinical presentation, computed tomography findings, surgical management, histopathological examination, and immunohistochemical results. Results: A 47 year old multiparous woman presented with six months of progressive abnormal uterine bleeding and abdominal enlargement. Non contrast computed tomography revealed a well circumscribed intramural uterine mass measuring 7.0 × 6.8 × 7.0 cm without detectable extrauterine disease. Total abdominal hysterectomy was performed for presumed leiomyoma. Gross examination revealed a firm whorled mass without evident hemorrhage or geographic necrosis. Microscopy demonstrated moderate to severe cytologic atypia, coagulative tumor cell necrosis, and more than 10 mitoses per 10 high power fields. Strong desmin and h caldesmon positivity supported smooth muscle differentiation. The patient was referred for multidisciplinary oncologic assessment. Conclusions: Benign appearing imaging and gross morphology cannot exclude uterine leiomyosarcoma. Accurate diagnosis requires adequate histological sampling and integrated clinicopathological assessment.