[Clinicopathological characteristics of anti-PD-1 associated gastroenteritis].

Objective: To investigate the clinicopathological features of anti-PD-1 related gastroenteritis, understand and recognize the disease, and avoid misdiagnoses. Methods: Three cases of anti-PD-1 related gastroenteritis diagnosed and treated at the Zhongshan Hospital Affiliated to Fudan University, Shanghai, China from 2020 to 2021 were collected. The clinical and pathological features were analyzed and the patients were followed up by telephone. Results: The three patients were all male and aged 63, 39 and 73 years, respectively. They had previously developed gastrointestinal symptoms as a result of immunotherapy for a malignant tumor. Endoscopically, 2 patients presented with pancolitis, and 1 patient presented with a large antral ulcer involving the pyloric canal in the stomach. Histologically, there were marked atrophy and thinning of the epithelium, diffuse infiltration of numerous neutrophils in the lamina propria, formation of micro-abscesses in the crypt/glandular lumen, structural changes (branching and distortion) of the glands, and significant glandular dilatation. In addition, chronic inflammatory features (e.g., lymphoplasmacytosis) were focally seen in 2 cases. Cytomegalovirus immunohistochemical stains were negative in all 3 cases. Based on the history and morphology, all 3 cases were diagnosed as anti-PD-1 related gastroenteritis. According to the above diagnosis, the treatment for all 3 patients was to stop anti-PD-1 therapy and use corticosteroids. Clinical follow-up was conducted. The gastrointestinal symptoms of all 3 patients improved significantly and diarrhea symptoms were relieved after stopping immunotherapy. Conclusions: Anti-PD-1 related gastroenteritis is not rare, but pathologists may lack sufficient understanding of it. Combined with clinical history and pathologic characteristics of the lesion, pathologists should consider this disease to avoid the misdiagnoses and missed diagnoses.目的： 探讨抗程序性细胞死亡受体1（PD-1）相关性胃肠炎的临床病理学特征，加深对该疾病的认知，避免误诊、漏诊。 方法： 收集2020—2021年复旦大学附属中山医院诊治的抗PD-1相关性胃肠炎3例。分析其临床特点、病理形态学特征，电话随访患者。 结果： 3例患者均为男性，年龄分别为63、39和73岁，此前均因恶性肿瘤免疫治疗而出现胃肠道症状。内镜检查2例表现为全结肠炎，1例表现为胃窦巨大溃疡并累及幽门管。显微镜下观察3例均主要表现为上皮明显萎缩、变薄，黏膜固有层大量中性粒细胞弥漫浸润，隐窝/腺腔内微脓肿形成，腺体减少及结构改变（分支、扭曲），部分腺体可有明显扩张。此外，2例局部区域还可见慢性炎症特征（如淋巴细胞、浆细胞增多）。3例行巨细胞病毒免疫组织化学染色，结果均为阴性。结合病史及形态学，3例均诊断为抗PD-1相关性胃肠炎。针对上述诊断，对3例患者的治疗方案均为停止抗PD-1治疗和使用皮质类固醇，并进行了临床随访。3例患者的胃肠道症状均明显改善，腹泻症状得到了缓解。 结论： 抗PD-1相关性胃肠炎临床上并不罕见，然而，病理医师对它缺乏足够关注及认识，结合临床病史及病理形态学特征，应当想到该疾病，避免误诊、漏诊。.