Pulmonary large cell carcinoma, highly positive for PD-L1, shows marked response to pembrolizumab: A case report.

Pulmonary large cell carcinoma (LCC) is classified as a poorly defined entity among non-small cell lung cancers (NSCLCs). At present, there are no effective anticancer drugs, such as molecular targeted drugs, for LCC, and it has been reported that patient prognosis is poor. Recently, the development of immune checkpoint inhibitors (ICIs) has changed the therapeutic strategies for patients with NSCLC. Here, we present a case of LCC successfully treated with pembrolizumab. A 58-year-old man who was a former smoker was diagnosed with LCC. The postoperative stage was T3N2M0. During postoperative adjuvant chemotherapy, swelling of the supraclavicular lymph node was observed and the patient was diagnosed with recurrence. The patient was treated with two regimens of conventional cytotoxic chemotherapy; however, he experienced some hoarseness. Imaging confirmed swelling of the hilar and mediastinal lymph nodes and the patient was subsequently diagnosed with disease progression. Previous surgical specimens when immunostained showed that a high proportion of the tumor cells were positive for expression of programmed death-ligand 1 (PD-L1), and it was decided to commence treatment with pembrolizumab. This treatment resulted in rapid regression of the hilar and mediastinal lymph nodes, and a progression-free period maintained for at least 24 treatment cycles. The patient's hoarseness improved, and the lymph nodes decreased in size. Immunotherapy targeting PD-1/PD-L1 may be an option for patients with PD-L1 positive LCC. This case report suggests that treatment with ICIs may be important in the selection of treatment for not only LCC but also relatively rare NSCLC with high PD-L1 expression.