Uterine Smooth Muscle Tumor of Uncertain Malignant Potential (STUMP): A Case Report

Uterine smooth muscle tumors of uncertain malignant potential (STUMP) are rare mesenchymal neoplasms that occupy a diagnostic gray zone between benign leiomyomas and malignant leiomyosarcomas. Owing to their low incidence and overlapping clinical, radiological, and histopathological features, STUMPs pose significant diagnostic and therapeutic challenges and are frequently identified only after surgical intervention for presumed benign disease. We report the case of a 39-year-old Mexican woman with a two-year history of abnormal uterine bleeding (AUB) and severe dysmenorrhea. Preoperative imaging findings were consistent with an intramural uterine mass and diffuse adenomyosis. The patient underwent a total abdominal hysterectomy with bilateral salpingectomy. Histopathological examination revealed a smooth muscle tumor characterized by focal nuclear atypia, a low mitotic index of up to 2 mitoses per 10 high-power fields, and absence of coagulative tumor cell necrosis (CTCN), findings consistent with a diagnosis of STUMP. The postoperative course was uneventful, and the patient was referred for long-term clinical surveillance. This report constitutes the first indexed case of STUMP in a Mexican patient and underscores the importance of thorough histopathological evaluation for accurate diagnosis, as well as the relevance of structured long-term follow-up given the potential for delayed recurrence.