DOI: https://doi.org/10.36347/sjmcr.2026.v14i07.027

Pages: 1727-1731

Leiomyosarcoma (LMS) is a rare malignant mesenchymal neoplasm arising from smooth muscle cells and accounts for approximately 10–20% of all soft tissue sarcomas (WHO Classification of Tumours Editorial Board, 2020). Retroperitoneal leiomyosarcoma is an uncommon subtype that frequently presents at an advanced stage because of its deep anatomical location and nonspecific clinical manifestations. We report the case of a 57-year-old man who presented with progressive unintentional weight loss, excessive sweating, and a palpable left-sided abdominal mass. Contrast-enhanced computed tomography demonstrated a 12.0 × 15.0 × 16.0 cm well-defined, lobulated, heterogeneously enhancing retroperitoneal soft tissue mass with areas of central necrosis causing mild left hydronephrosis due to mass effect. Staging investigations identified multiple bilateral pulmonary nodules suspicious for metastatic disease. The patient underwent exploratory laparotomy with complete surgical excision of the tumour. Histopathological examination confirmed FNCLCC Grade 2 retroperitoneal leiomyosarcoma (pT3) with microscopically negative surgical margins (R0). Immunohistochemistry demonstrated positivity for caldesmon, desmin, smooth muscle actin (SMA), and CD117, while DOG1, CD34, S100, STAT6, MDM2, CAM5.2, and ERG were negative, supporting the diagnosis of leiomyosarcoma. Following multidisciplinary sarcoma team discussion, the patient commenced systemic chemotherapy for metastatic disease. This case highlights the diagnostic challenges associated with retroperitoneal leiomyosarcoma and underscores the importance of early diagnosis, complete surgical resection, accurate histopathological evaluation, and multidisciplinary management in optimising patient outcomes.