Primary proximal epithelioid sarcoma of the lung: A case report and review of the literature.

Epithelioid sarcoma (ES) is a rare mesenchymal tumor that can be divided into proximal/axial type and classical/distal type. Primary proximal epithelioid sarcoma of the lung is extremely rare. So far, no more than five cases have been reported. We reported a case of primary pulmonary ES and reviewed the literature to summarize its clinicopathological features. A 51-year-old man presented with hemoptysis and cough. Chest computed tomography (CT) showed a nodule located in the apical and posterior segments of the left upper lobe of the lung. The patient underwent a lobectomy, and a pathologic diagnosis of epithelioid sarcoma was made. Histologically, most tumors are composed of epithelioid cells with evidence of bidirectional expression of epithelium and mesenchyma. The SMARCB1 stain of tumor cells was negative, and a pathogenic mutation of SMARCB1 p.E115* (exon 3) were identified by the next-generation sequencing. Two months after surgery, positron emission tomography/computed tomography (PET/CT) indicated tumor recurrence, and the patient received a round of adjuvant chemotherapy combined with immunotherapy. After 11 months of follow-up, the patient died. We reported in detail the primary proximal epithelioid sarcoma of the lung treated with immunotherapy for the first time, providing ideas for diagnosis and treatment.