Pulmonary pleomorphic carcinoma in an elderly patient treated with pembrolizumab shows a marked response.

Pulmonary pleomorphic carcinoma, a relatively rare histopathological subtype of non-small cell lung cancer, is a malignant neoplasm with a poor prognosis. Despite the reports of a good response to immune-checkpoint inhibitor, only a few reports of pembrolizumab as the first-line treatment exist. We report the case of a 78-year-old male with right lung mass, mediastinal, right neck, and supraclavicular lymphadenopathies. He was diagnosed with pulmonary pleomorphic carcinoma, cT4N3M1c, Stage IVB. The tumor cells showed high programmed death-ligand 1 (PD-L1) expression but no microsatellite instability. After three cycles of pembrolizumab as the first-line therapy, chest computed tomography revealed marked reduction in tumor diameter. No remarkable adverse events occurred. The patient is alive with no complaints and no disease progression and has continued pembrolizumab for 8 months. Thus, first-line pembrolizumab therapy appears beneficial against pulmonary pleomorphic carcinoma, at least when PD-L1 expression is high. It is also effective in elderly patients.