Smooth Muscle Tumor of Uncertain Malignant Potential Masquerading as Sarcoma

Smooth muscle tumor of uncertain malignant potential (STUMP) is a rare uterine neoplasm with histopathological features intermediate between benign leiomyoma and leiomyosarcoma, posing significant diagnostic and management challenges.

A 41-year-old woman presented with abdominal pain and distension. Examination revealed a large abdominal mass occupying all quadrants. MRI demonstrated a 20 × 18 × 16 cm exophytic sub-serosal fundal mass extending to the epigastrium, with extensive cystic degeneration suggestive of sarcomatous change. She underwent exploratory laparotomy with total abdominal hysterectomy and bilateral salpingo-oophorectomy. Intraoperatively, a large uterine fundal mass with extensive neovascularization was identified. Final histopathological examination and immunohistochemistry confirmed the diagnosis of STUMP.

This case highlights the difficulty in preoperative differentiation between benign leiomyomas and premalignant or malignant uterine smooth muscle tumors. Definitive diagnosis relies on histopathological and immune-histochemical assessment, underscoring the importance of appropriate surgical management and long-term surveillance in patients diagnosed with STUMP.