Pulmonary pleomorphic carcinoma with pseudoprogression during nivolumab therapy and the usefulness of tumor markers: A case report.

Pseudoprogression was reported as one of the unconventional responses during immune checkpoint inhibitor therapy. A 70-year-old man with pulmonary pleomorphic carcinoma received nivolumab therapy. Pleural effusion and pulmonary metastasis increased, however then shrank and serum cytokeratin 19 fragment levels decreased. Serum tumor marker might help to distinguish pseudoprogression.