Primary leiomyosarcoma of the thoracic outlet: case report and surgical approach

Background: Leiomyosarcoma represents a small portion of soft tissue sarcomas, most commonly affecting adults between 40 and 60 years of age. While these tumors typically arise in the retroperitoneum and uterus, involvement of the thoracic outlet is exceedingly rare. Management of thoracic outlet tumors poses unique surgical challenges due to the proximity of critical neurovascular structures, and no standardized approach has been established. Case Description: A 68-year-old woman presented with a slowly enlarging, painless left neck mass that was complicated by intermittent swelling and left upper extremity deep venous thrombosis. Imaging revealed a 9-cm soft tissue tumor partially occluding the left subclavian vein without evidence of distant metastases. Immunohistochemistry of the core needle biopsy confirmed leiomyosarcoma. After multidisciplinary tumor board review, surgical resection was pursued for local control. The patient underwent en bloc resection through a partial sternal split and transclavicular approach, enabling safe exposure of the thoracic outlet. The mass was resected with the involved segment of the left subclavian vein, followed by reconstruction with an interposition polytetrafluoroethylene (PTFE) graft to restore central venous inflow. Intraoperative frozen section confirmed negative margins. Postoperative recovery was notable for a transient chyle leak, which resolved with conservative dietary management. The patient was discharged in stable condition on postoperative day 5. At 3-month follow-up, the patient reported good overall recovery, and surveillance imaging showed no evidence of recurrence or metastatic disease. Conclusions: This case represents an extremely rare instance of thoracic outlet leiomyosarcoma involving the subclavian vein that was successfully resected using the partial sternal split and partial claviculectomy approach. Our experience highlights the value of advanced multidisciplinary planning and tailored surgical techniques to achieve complete resection in anatomically complex regions. Broader documentation and study of such cases will be critical to establishing best practices for rare and challenging tumors of the thoracic outlet.