Successful treatment with nivolumab for lung cancer with low expression of PD‐L1 and prominent tumor‐infiltrating B cells and immunoglobulin G

: Little is known about the anti-tumor activity of humoral immunity in lung cancer patients treated with nivolumab, an immune checkpoint inhibitor. Herein, we report a case of lung cancer with 5% expression of PD-L1, in which a partial response to nivolumab was sustained for > 7 months. Immunohistochemical analysis of the metastatic lymph node biopsy specimen showed prominent accumulation of plasma cells and immunoglobulin G. These findings suggest that pre-existing humoral immunity may be worth considering as a candidate therapeutic biomarker of nivolumab in some lung cancer patients.