[A Case of Specific Pneumonia Diagnosed as Peritumoral Infiltration during Nivolumab Treatment for Esophageal Cancer].

The patient is a 54-year-old man who was diagnosed with advanced unresectable esophageal cancer. He underwent three courses of FP therapy and was followed up for observation after chemoradiotherapy and PR. Metastasis appeared in the upper lobe of the left lung and new lung metastasis was found in the lower lobe of the right lung despite FP therapy 2 years and 1 month after the start of treatment. Nedaplatin and docetaxel were administered as a second-line chemotherapy; however, the lung metastasis worsened. Consequently, nivolumab was introduced as a third-line chemotherapy. The metastases in the lower lobe of the right lung disappeared with pneumonia after 6 courses of nivolumab, which was diagnosed as a peritumoral infiltration(PTI). PTI is difficult to distinguish from drug-induced lung injury and should be diagnosed carefully because it is an imaging finding that reflects the desired antitumor effect.