Immune Checkpoint Inhibitor-induced Mass-forming Pancreatitis and Lipodystrophy: A Case Report and Review of the Literature.

Mass-forming pancreatitis and lipodystrophy are rare immune-related adverse events (irAEs). A 71-year-old woman received 12 cycles of pembrolizumab for recurrent uterine endometrial cancer. The patient presented with mass-forming pancreatitis and lipodystrophy. A needle biopsy of the pancreatic tissue revealed lymphocytic infiltration and fibrosis. Simultaneously, the patient exhibited lipodystrophy. The recurrent tumors disappeared, so the patient discontinued immune checkpoint inhibitor treatment and was administered oral prednisolone. In addition, the pancreatic mass disappeared; however, the fat loss did not improve. Considering pancreatitis and lipodystrophy to be irAEs, prompt management is important.