[A Case of Primary Amelanotic Malignant Melanoma of the Esophagus, Wherein Pseudoprogression Was Suspected during Immune Checkpoint Inhibitor Treatment].

A 78-year-old man was admitted to our hospital with a diagnosis of esophageal cancer and gastric cancer. Gastroscopy showed a type 2 tumor located in the cardia from the lower esophagus, and a pathological examination showed malignant melanoma. Based on the physical examination and other imaging tests, the patient was diagnosed with primary amelanotic malignant melanoma of the esophagus, but the tumor was unresectable due to extensive lymph node metastasis. According to the guideline, immune checkpoint inhibitor(nivolumab)was used for treatment, but because the tumor progressed after 2 courses and the performance status of the patient worsened, aggressive treatment was ended. Six weeks after finishing treatment, computed tomography showed that the tumor had shrunk to some extent. The patient ultimately died from aspiration pneumonia 4 months after the first consultation. The patient was thought to have had an immune-related adverse event, with the tumor showing pseudoprogression.