Salvage resection after immunotherapy for giant undifferentiated pleomorphic sarcoma of the chest wall.

We present a rare case of primary undifferentiated pleomorphic sarcoma (UPS) of the chest wall in a 45-year-old male, initially diagnosed as sarcomatoid pleural mesothelioma via computed tomography (CT)-guided biopsy. CT revealed a large tumor measuring 13 × 12 cm occupying the left thoracic cavity, with extensive invasion into the left first through fifth ribs and the adjacent lung parenchyma. The patient was referred to our hospital and treated with a combination of nivolumab and ipilimumab, resulting in marked tumor regression. Upon reevaluation, the diagnosis was revised to sarcoma, and the patient subsequently underwent salvage surgery, including resection of the left upper lung lobe and first through fifth ribs. Histopathology confirmed tumor mutational burden-high UPS. The patient has remained disease-free for two and a half years postoperatively. This case demonstrates the potential efficacy of immune checkpoint inhibitors in multimodal treatment for select cases of chest wall UPS.