Incidental Extraluminal Leiomyosarcoma of the Urinary Bladder: A Rare Diagnostic and Therapeutic Challenge

Abstract

Introduction: Non-urothelial malignancies in the bladder are rare. Leiomyosarcoma has been recognized as the most common mesenchymal tumor, accounting for less than 0.1% of primary bladder tumors. The diagnosis of leiomyosarcoma mostly relies on histopathological analysis and specific immunohistochemical markers, as clinical and imaging findings are typically inadequate. Case Report: We here describe the case of a 56-year-old female who presented with diffuse pain in the lower abdomen during micturition for one week. Whole body 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) imaging findings identified a faintly FDG-avid lesion in the anterior pelvic region raising the suspicion of a mesenteric mass. She underwent exploratory laparotomy, which revealed a 4x3 cm mass originating from the fundus of the bladder (extraluminal) with adhesions to the sigmoid colon. Histopathological examination of the resected mass confirmed it as a high-grade sarcoma of the urinary bladder with necrotic areas and high mitotic activity. The surrounding cuff of bladder tissue revealed no evidence of malignancy. The immunohistochemistry report results were positive for smooth muscle actin, desmin, and caldesmon supporting the diagnosis of leiomyosarcoma urinary bladder. Conclusion: This case underscores the rarity and diagnostic challenges associated with extraluminal leiomyosarcoma of the bladder. There is a need to consider leiomyosarcoma as differential diagnosis of atypical bladder masses highlighting the importance of a tailored, multidisciplinary approach, addressing the potential for recurrence, and improving patient outcomes. Continued reporting of cases and collaborative research efforts are essential to advance our understanding of this rare malignancy.