Endoscopic Ultrasound With Fine Needle Biopsy Confirming a Diagnosis of Immune Checkpoint Inhibitor‐Related Type 3 Autoimmune Pancreatitis

On biopsy, there was no evidence of malignancy or features of type 1 or type 2 AIP. Histologic findings included moderate infiltration and damage to the pancreatic parenchyma, ductal, and vascular structures by CD4 and CD8 lymphocytes, pointing to immune-mediated pancreatic injury, and supportive of ICI-mediated injury to the pancreas of this patient. The clinical presentation of type 3 AIP ranges from asymptomatic lipase elevation to asymptomatic pancreatitis to acute symptomatic pancreatitis. There may be no clear temporal relationship to treatment initiation. Type 3 AIP typically presents along with other immune-related adverse events. Endoscopic ultrasound with FNB contributed to diagnostic certainty in this case and changed our patient's management, allowing for appropriate treatment of his immune-related adverse event.