Pembrolizumab-induced Focal Pancreatitis Diagnosed by Endoscopic Ultrasound-guided Fine-needle Aspiration

Abstract

A 69-year-old man with advanced non-small-cell lung cancer was treated with pembrolizumab for 4 months. Three months after pembrolizumab was discontinued, computed tomography showed enlargement of the pancreatic head, with hypoattenuating areas in the pancreatic head to body. On endoscopic ultrasonography, the entire pancreatic parenchyma was hypoechoic. Endoscopic retrograde cholangiopancreatography showed narrowing of the main pancreatic duct at the pancreatic head. Endoscopic ultrasound-guided fineneedle aspiration showed inflammatory cell infiltration in the stroma but no neoplastic lesions. CD8-positve T cells were dominant over CD4-positive T cells in the infiltrating lymphocytes, and the patient was diagnosed with pembrolizumab-induced pancreatitis.

Immune Checkpoint Inhibitor-induced Pancreatitis with Pancreatic Enlargement Mimicking Autoimmune Pancreatitis: A Case Report and Review of the Literature

“…Previous reports showed that the lymphocytes were predominantly CD8-positive lymphocytes; however, no such predominance was observed in the present case. irAEs are caused by an immune response triggered by T-cell lympho- (32,33). However, in the present patient, CD4 cells may have played an important role in the pathogenesis, as there were multinucleated giant cells and reaction-forming granulomas with dense fibrosis, which may explain why a predominant infiltration of CD8+ T cells was not observed.…”

“…Similarly, ICI-induced pancreatitis may not require strong activation of helper T cells or immunoglobulin production. Ikemoto et al and Hirota et al reported that irAE-induced pancreatitis showed significant infiltration with CD8 lymphocytes ( 32 , 33 ). However, in the present patient, CD4 cells may have played an important role in the pathogenesis, as there were multinucleated giant cells and reaction-forming granulomas with dense fibrosis, which may explain why a predominant infiltration of CD8+ T cells was not observed.…”

“…In the present patient, there was no abdominal pain or elevated serum lipase level; however, a gradual worsening of pancreatic enlargement and intrapancreatic bile duct stenosis was observed. Asymptomatic ICI-induced pancreatitis was diagnosed because of an incidental detection of pancreatic enlargement and intrapancreatic bile duct stenosis ( 15 , 32 , 34 ). Therefore, patients using ICIs should be regularly checked for the occurrence of irAEs using several imaging modalities, even in the absence of symptoms.…”