Abstract
A 70-year-old man underwent nephrectomy for renal cell carcinoma followed by 3 cycles of pembrolizumab as adjuvant chemotherapy. Three months later, he complained of appetite loss. He was diagnosed with secondary adrenal insufficiency and pancreatic tumor. Amylase and immunoglobulin G (IgG) 4 levels were normal. The differential diagnosis poses challenges in distinguishing pancreatic cancer, renal cell carcinoma metastasis, and autoimmune pancreatitis, necessitating tumor resection surgery. A histological examination revealed IgG4-related sclerosing pancreatitis. Postoperatively, there was no recurrence of pancreatitis. It is essential to consider the potential development of IgG4-related diseases after the administration of immune checkpoint inhibitors.