Pembrolizumab-induced gastritis with PDL1 histological expression

Immune-mediated gastritis is a rare adverse effect in patients treated with immune checkpoint inhibitors. We present a patient with a diagnosis of cervical carcinoma under treatment with pembrolizumab who was admitted with nausea, vomiting and weight loss; an endoscopy revealed a ulcerated lesion covered by mucus in the antrum and gastric body. The biopsy revealed extensive denudation of the gastric mucosa with fibrin leukocyte reaction. Into the lamina propria, an increased lymphocytic and polymorphonuclear inflammatory infiltrate was observed. Immunohistochemistry confirmed positivity for PDL1 (clone SP2630) and combined positive score of 35%, with a relative contribution of epithelial cells of 25% and inflammatory cells of 10%. After three weeks with 30 mg meprednisone, a new endoscopy revealed a stomach with clear mucus content; fundus and body without lesions, and an antrum with congestive mucosa and multiple superficial ulcers covered by fibrin. Diagnostic and therapeutic aspects of immune-mediated gastritis are described.