Anti-PD-1 induced collagenous colitis in metastatic melanoma: a rare severe adverse event

Histopathologic Manifestations of Immune Checkpoint Inhibitor Therapy-Associated Gastrointestinal Tract Injury: A Practical Review

Immune checkpoint inhibitors have revolutionized the management of many advanced cancers by producing robust remissions. They mostly target two immune regulatory pathways: cytotoxic T lymphocyte antigen-4 and programmed death-1 or its ligand. However, a flip side is the immune-related adverse events (irAEs) commonly affecting the gastrointestinal (GI) tract that can cause treatment interruptions or discontinuation. This practical review discusses the clinical and histopathologic findings of irAEs encountered in the luminal GI tract, along with histopathologic differentials that can mimic varied inflammatory, infectious, or other medication-associated etiologies and the importance of clinico-pathologic correlation for an accurate diagnosis.

Gastrointestinal and Hepatobiliary Immune-related Adverse Events: A Histopathologic Review

Immune checkpoint inhibitors have been increasingly used to treat various malignant neoplasms. Despite their superior efficacy in treating certain ones, their global immune-activation effect leads to systemic side effects, referred to as immune-related adverse events. Immune-related adverse events affect a variety of organs, including the skin, gastrointestinal, hepatobiliary, and endocrine organs. Gastrointestinal tract immune-related adverse events present with a wide range of symptoms with variable severity, which may lead to treatment interruption and administration of immunosuppression therapy in many cases. Histopathologic changes are diverse, overlapping with many other conditions. Therefore, recognizing these changes is crucial in diagnosing immune-related adverse events. This review discusses the pathologic manifestations of gastrointestinal immune-related adverse events and discusses the primary differential diagnoses.

Drug-induced digestive tract injury: decoding some invisible offenders

There is an ever-growing list of pharmacological agents, several of which are attributed to cause clinically significant gastrointestinal (GI) injury. Many patients present with significant but nonspecific symptoms, that in conjunction with the absence of relevant drug history on the requisition slip can make the histopathologic diagnosis challenging. To complicate this, although some drugs have relatively characteristic histopathologic features (such as doxycycline), there exist many other drugs that exhibit wide and varying spectra of histopathologic findings (such as immune checkpoint inhibitors or olmesartan) and have histomorphologic overlap with many other commonly encountered disease entities. This review discusses the histopathologic features of some relatively recently described drugs causing GI tract injury, namely doxycycline, tacrolimus, mycophenolate, immune checkpoint inhibitors, and olmesartan. We also discuss the common mimics in histopathologic differential and some pearls that can help distinguish GI tract injury induced by the aforementioned drugs from its mimics. Awareness of the wide spectra of histopathologic changes associated with these drugs is crucial for practicing pathologists, to avoid misdiagnosis and guiding the clinician for an optimal patient management, which usually involves modifying or discontinuing the offending drug. Needless to say, once a diagnosis of drug-induced injury is suspected, clinicopathologic correlation including corroboration with the drug history is of utmost importance as is the exclusion of dual pathology in these patients.

Gastrointestinal and Hepatobiliary Immune-related Adverse Events: A Histopathologic Review

Immune checkpoint inhibitors have been increasingly used to treat various malignant neoplasms. Despite their superior efficacy in treating certain ones, their global immune-activation effect leads to systemic side effects, referred to as immune-related adverse events. Immune-related adverse events affect a variety of organs, including the skin, gastrointestinal, hepatobiliary, and endocrine organs. Gastrointestinal tract immune-related adverse events present with a wide range of symptoms with variable severity, which may lead to treatment interruption and administration of immunosuppression therapy in many cases. Histopathologic changes are diverse, overlapping with many other conditions. Therefore, recognizing these changes is crucial in diagnosing immune-related adverse events. This review discusses the pathologic manifestations of gastrointestinal immune-related adverse events and discusses the primary differential diagnoses.

Endoscopic and histopathologic features of Anti‐PD‐1‐related collagenous colitis

Objectives

Cancer patients treated with immune checkpoint inhibitors occasionally show persistent diarrhea accompanied by endoscopic features of ulcerative colitis. The endoscopic mucosal inflammation may appear mild in some patients compared to the clinical severity, which can make choosing a treatment challenging. In this study, we evaluated the factors that support the continuation of chemotherapy by assessing the endoscopic and histopathological characteristics of patients who experienced diarrhea after immune checkpoint inhibitor administration.

Methods

This study included eight patients who were diagnosed with collagenous colitis based on pathological assessments. We retrospectively investigated these patients’ backgrounds, laboratory data, and computed tomography images that were extracted from their medical records. We also summarized their endoscopic and pathologic findings.

Results

All eight patients were being treated with anti‐programmed cell death‐1/programmed cell death‐ligand 1 therapeutic agents and had a recent history of oral proton pump inhibitor therapy. The anti‐programmed cell death‐1‐related collagenous colitis in these cases was characterized by endoscopically mild mucosal inflammation, high fecal calprotectin levels, and a lower frequency of intestinal wall thickening on computed tomography. Histological assessments showed CD8⁺ lymphocytes predominantly infiltrating the lamina propria and crypts of the colonic mucosa. Suspending the proton pump inhibitor therapy relieved the patients’ symptoms and allowed the continuation of the anti‐programmed cell death‐1/programmed cell death‐ligand 1 therapy.

Conclusions

Anti‐programmed cell death‐1‐related collagenous colitis is reversible; appropriate diagnosis of adverse events is crucial for the continuation of immune checkpoint inhibitor therapy.