Pulmonary sarcomatoid carcinoma with METex14 mutation and high PD-L1: A case report

RATIONALE: Pulmonary sarcomatoid carcinoma (PSC) is a rare and aggressive subtype of lung cancer, posing diagnostic and therapeutic challenges. Cases of PSC harboring both MET exon 14 skipping (METex14) mutation and high PD-L1 expression are rarely documented, and reports detailing multimodal treatment involving surgery, chemotherapy, targeted therapy, and immunotherapy in such patients are even scarcer. PATIENT CONCERNS: A 54-year-old man presented with a persistent cough for over half a month. He was previously healthy. Physical examination revealed diminished breath sounds in the right upper lung. DIAGNOSES: Initial bronchoscopic biopsy suggested inflammation, and computed tomography (CT)-guided lung biopsy showed atypical giant cells but was inconclusive. Following multidisciplinary team discussion, the patient underwent surgical resection. Postoperative pathology confirmed pleomorphic carcinoma (sarcomatoid carcinoma). Subsequent genetic testing identified a METex14 mutation with high PD-L1 expression (Tumor Proportion Score ≥ 50%). The final diagnosis was stage IIIB (T4N2M0) right PSC, MET-positive, PD-L1-positive. INTERVENTIONS: The initial treatment plan included 1 cycle of toripalimab (an anti-PD-1 antibody) combined with docetaxel and lobaplatin chemotherapy. This was subsequently adjusted to boretinib (a MET inhibitor) targeted therapy combined with docetaxel and lobaplatin chemotherapy. OUTCOMES: The patient achieved and maintained a partial response (PR) for over 6 months of follow-up. Symptoms including cough resolved, and his general condition remained good with satisfactory appetite and sleep. LESSONS: This case underscores the diagnostic difficulty of PSC, which is prone to misdiagnosis and exhibits rapid growth. Surgery may not be appropriate for unresectable stage IIIB PSC. Gene sequencing and PD-L1 testing are crucial as they expand therapeutic options for PSC patients. The optimal first-line therapy (targeted vs immunotherapy) for PSC with concurrent MET mutation and high PD-L1 expression remains undefined, warranting further exploration of combination strategies.