A case of leiomyosarcoma originating from the azygos vein.

Leiomyosarcoma is a soft-tissue sarcoma that accounts for less than 1% of all malignant tumors. Furthermore, leiomyosarcoma accounts for 6% of all soft tissue sarcomas, and leiomyosarcoma of azygos vein origin is extremely rare. In this report, we describe a case of leiomyosarcoma derived from an azygos vein that was completely resected. A 78-year-old male patient was incidentally found to have a mediastinal mass during a computed tomography (CT) scan performed for the evaluation of prostate cancer. Bronchoscopic needle biopsy revealed the mass to be a leiomyosarcoma. Preoperative contrast-enhanced CT demonstrated a filling defect in the azygos vein, suggesting the tumor's origin from this structure. Video-assisted thoracoscopic surgery (VATS) was performed to resect the mediastinal tumor. The tumor was found to have minimal adhesions to surrounding tissues and no evidence of local invasion, although findings suggested it originated from the azygos vein. Consequently, en bloc resection of the azygos vein was performed. Postoperative histopathological examination confirmed the diagnosis of leiomyosarcoma originating from the azygos vein, and complete resection was performed.