Real-world genetic testing outcomes of pan-cancer testing for mismatch repair deficiency.

BACKGROUND: In 2017, the Food and Drug Administration approved pembrolizumab for treatment of any mismatch repair-deficient (dMMR) tumor making MMR immunohistochemistry (IHC) testing beneficial for all tumor types. For the first time, MMR IHC was not performed exclusively to screen for Lynch syndrome (LS). METHODS: In this study, all MMR IHC reports issued between 2017 and 2021 at an academic hospital were reviewed and completion of genetic testing was determined through chart review. Colorectal cancers (CRCs), endometrial cancers (ECs), and noncancerous lesions were excluded. RESULTS: Between 2017 and 2021, MMR IHC was completed in 1939 patients with a malignancy other than CRC or EC. Absent or weak staining for at least one MMR protein was detected in 115 (5.9%) patients and 59 (51%) of those completed germline genetic testing. Overall, the identification rate of LS in this cohort was 0.72%, which is similar to the rate in our previously reported CRC and EC universal screening cohort. A diagnosis of LS was most commonly made in patients with dMMR brain (18.75%) and small intestinal cancers (10.20%). Five additional patients were found to carry a pathogenic variant in a non-LS gene. CONCLUSIONS: Pan-cancer MMR testing for pembrolizumab consideration can identify LS cases at a rate similar to universal CRC and EC screening programs. A persistent challenge is subsequent uptake of genetic testing. MMR testing should be prioritized in brain and small intestinal tumors, and multigene panel testing is recommended in patients with dMMR, as unexpected pathogenic variants in non-LS genes were found as frequently as LS gene variants.

Defining an abnormal p53 immunohistochemical stain in Barrett's oesophagus-related dysplasia: a single-positive crypt is a sensitive and specific marker of dysplasia.

AIMS: p53 is an independent risk stratification marker in Barrett's oesophagus (BE), but no universally accepted definition exists for abnormal p53 staining. Herein, we assess p53 stains in two cohorts to: (1) define abnormal p53 staining in BE-related dysplasia (BERD) and (2) assess the specificity and sensitivity of this cut-point for the diagnosis of dysplasia. METHODS: Cohort 1 (n = 313) included (1) dysplastic BE biopsies, (2) prior non-dysplastic BE (NDBE) biopsies from the same patients and (3) NDBE biopsies from patients who never progressed to dysplasia. Cohort 2 (n = 191) consisted of BE biopsies in which p53 staining aided in diagnosing dysplasia. Automated p53 staining quantification was performed on cohort 1. A semiquantitative p53 analysis, performed on both cohorts, included: (1) number of strongly positive glands, (2) strong glandular surface staining, (3) percentage of strongly positive glands and (4) null phenotype. RESULTS: NDBE biopsies from cohort 1 patients who progressed to dysplasia were more likely to show p53 positivity than non-progressors (16.9 versus 0.6%) (P = 0.0001). The optimal quantitative cut-point for distinguishing dysplastic from never-dysplasia biopsies was 10 strongly positive cells. By semiquantitative analysis, a single strongly p53-positive gland distinguished dysplastic from never-dysplasia BE (sensitivity 98.6%, specificity 99.4%). The semiquantitative and quantitative analyses correlated (P = 0.0001). In cohort 2, the sensitivity and specificity for BERD of ≥ 1 strongly positive p53 gland were 86.0 and 88.6%. CONCLUSIONS: A single strongly positive p53 gland is sensitive and specific for BERD. Automated p53 analysis may reduce subjectivity associated with the diagnosis of BERD.

Clinicopathological findings in patients with COVID-19-associated ischaemic enterocolitis.

AIMS: Coronavirus disease 2019 (COVID-19) has been recognised as a predominantly respiratory tract infection, but some patients manifest severe systemic symptoms/coagulation abnormalities. The aim of this study was to evaluate the impact of severe COVID-19 infection on the gastrointestinal tract. METHODS AND RESULTS: We examined clinicopathological findings in 28 resected ischaemic bowels from 22 patients with severe COVID-19. Most patients required intubation preoperatively and presented with acute decompensation shortly before surgery. D-dimer levels were markedly elevated in all measured cases (mean, 5394 ng/ml). Histologically, 25 cases (19 patients) showed evidence of acute ischaemia with necrosis. In this group, the most characteristic finding was the presence of small vessel fibrin thrombi (24 of 25 cases, 96%), which were numerous in 64% of cases. Patients with COVID-19 were significantly more likely than a control cohort of 35 non-COVID-19-associated acute ischaemic bowels to show isolated small intestine involvement (32% versus 6%, P < 0.001), small vessel fibrin thrombi (100% versus 43%, P < 0.001), submucosal vessels with fibrinous degeneration and perivascular neutrophils (90% versus 54%, P < 0.001), fibrin strands within submucosal vessels (58% versus 20%, P = 0.007), and histological evidence of pneumatosis (74% versus 34%, P = 0.010). Three cases in this cohort had histopathological findings normally seen in the setting of chronic ischaemia, notably prominent fibroblastic proliferation affecting the outer layer of the muscularis propria. CONCLUSIONS: Herein, we describe the histopathological findings in COVID-19-associated ischaemic bowels and postulate a relationship with the hypercoagulable state seen in patients with severe COVID-19 infection. Additional experience with these cases may further elucidate specific features or mechanisms of COVID-19-associated ischaemic enterocolitis.

Actinomyces in Crohn's-like appendicitis.

AIMS: Appendicitis with a Crohn's-like histological appearance generally raises concern for Crohn's disease, Yersinia infection, and interval appendectomy. Actinomyces infection is a recognised cause of chronic appendicitis that can histologically mimic Crohn's disease. METHODS AND RESULTS: We report on 20 cases of appendicitis with Crohn's-like histological features that were due to Actinomyces. Most patients presented with acute or chronic abdominal pain. Imaging studies suggested a mass in five cases. Two patients had interval appendectomy. Histological features showed Crohn's-like appendicitis in 16 cases, with moderate to marked fibrosis and granulomas in seven cases. The other four cases had less consistent histological findings. None of the patients developed Crohn's disease during the follow-up interval (median, 37 months). CONCLUSIONS: Actinomyces can be associated with Crohn's-like appendicitis with marked fibrosis, transmural inflammation, lymphoid hyperplasia, and granulomas.

Universal screening of both endometrial and colon cancers increases the detection of Lynch syndrome.

BACKGROUND: Lynch syndrome (LS) is the most common hereditary cause of colorectal cancer (CRC) and endometrial cancer (EC). Screening of all CRCs for LS is currently recommended, but screening of ECs is inconsistent. The objective of this study was to determine the added value of screening both CRC and EC tumors in the same population. METHODS: A prospective, immunohistochemistry (IHC)-based screening program for all patients with newly diagnosed CRCs and ECs was initiated in 2011 and 2013, respectively, at 2 centers (primary and tertiary). Genetic testing was recommended for those who had tumors with absent mutS homolog 2 (MSH2), MSH6, or postmeiotoic segregation increased 2 (PMS2) expression and for those who had tumors with absent mutL homolog 1 (MLH1) expression and no v-Raf murine sarcoma viral oncogene homolog B (BRAF) mutation or MLH1 promoter methylation. Amsterdam II criteria, revised Bethesda criteria, and scores from prediction models for gene mutations (the PREMM1,2,6 and PREMM5 prediction models) were ascertained in patients with LS. RESULTS: In total, 1290 patients with CRC and 484 with EC were screened for LS, and genetic testing was recommended for 137 patients (10.6%) and 32 patients (6.6%), respectively (P = .01). LS was identified in 16 patients (1.2%) with CRC and in 8 patients (1.7%) with EC. Among patients for whom genetic testing was recommended, the LS diagnosis rate was higher among those with EC (25.0% vs 11.7%, P = .052). The Amsterdam II criteria, revised Bethesda criteria, and both PREMM calculators would have missed 62.5%, 50.0%, and 12.5% of the identified patients with LS, respectively. CONCLUSIONS: Expanding a universal screening program for LS to include patients who had EC identified 50% more patients with LS, and many of these patients would have been missed by risk assessment tools (including PREMM5 ). Universal screening programs for LS should include both CRC and EC. Cancer 2018. © 2018 American Cancer Society.

A tailored approach to BRAF and MLH1 methylation testing in a universal screening program for Lynch syndrome.

To determine the correlation between BRAF genotype and MLH1 promoter methylation in a screening program for Lynch syndrome (LS), a universal screening program for LS was established in two medical centers. Tumors with abnormal MLH1 staining were evaluated for both BRAF V600E genotype and MLH1 promoter methylation. Tumors positive for both were considered sporadic, and genetic testing was recommended for all others. A total 1011 colorectal cancer cases were screened for Lynch syndrome, and 148 (14.6%) exhibited absent MLH1 immunostaining. Both BRAF and MLH1 methylation testing were completed in 126 cases. Concordant results (both positive or both negative) were obtained in 86 (68.3%) and 16 (12.7%) cases, respectively, with 81% concordance overall. The positive and negative predictive values for a BRAF mutation in predicting MLH1 promoter methylation were 98.9% and 41%, respectively, and the negative predictive value fell to 15% in patients ≥70 years old. Using BRAF genotyping as a sole test to evaluate cases with absent MLH1 staining would have increased referral rates for genetic testing by 2.3-fold compared with MLH1 methylation testing alone (31% vs 13.5%, respectively, P<0.01). However, a hybrid approach that reserves MLH1 methylation testing for BRAF wild-type cases only would significantly decrease the number of methylation assays performed and reduce the referral rate for genetic testing to 12.7%. A BRAF mutation has an excellent positive predictive value but poor negative predictive value in predicting MLH1 promoter methylation. A hybrid use of these tests may reduce the number of low-risk patients referred to genetic counseling and facilitate wider implementation of Lynch syndrome screening programs.

Cytologic, histologic, and molecular features of pancreatic sarcomatoid undifferentiated carcinoma with heterologous osteosarcomatous transformation.

Fine-needle aspiration (FNA) is a minimally invasive and effective modality to diagnose pancreatic ductal adenocarcinoma. However, some histologic subtypes of ductal adenocarcinoma are rarely encountered and challenging to diagnose on FNA/small biopsies. To date, cytohistologic features of pancreatic sarcomatoid undifferentiated carcinoma with heterologous elements have not been thoroughly described. An 83-year-old man with lower back pain was found to have an incidental pancreatic neck mass. FNA biopsy of the mass showed rare markedly atypical, large, pleomorphic cells in a background of abundant calcifications/bone formation without areas of conventional adenocarcinoma. A diagnosis of "Malignant neoplasm with osteosarcomatous differentiation" was rendered on the FNA specimen. Subsequently, a Whipple resection revealed a 4.1 cm lobulated, calcified pancreatic mass. Microscopic examination showed a heavily calcified/ossified mass with adjacent areas of a highly cellular malignant spindle cell proliferation and admixed large, pleomorphic tumor cells; no background conventional adenocarcinoma was identified. Cytokeratin immunostains MNF116 and CK19 were positive in a large subset of the malignant spindle cells, and AE1.3/CAM5.2 showed patchy weak staining. Molecular testing revealed mutations in KRAS, TP53, BRCA2, NTRK3, EPHA2, MYD88, and CBL. No reportable fusions were detected. The final diagnosis was "Sarcomatoid undifferentiated carcinoma with heterologous elements (osteosarcomatous differentiation)." Definitive diagnosis of extremely rare subtypes of ductal adenocarcinoma is challenging on FNA biopsies. In this case, cytologic evaluation was helpful in making an early diagnosis of a malignant neoplasm with highly unusual features, prompting appropriate triage and early surgical resection of a sarcomatoid undifferentiated carcinoma with prominent osteosarcomatous differentiation.

Agrin Loss in Barrett's Esophagus-Related Neoplasia and Its Utility as a Diagnostic and Predictive Biomarker.

PURPOSE: There is an unmet need for identifying novel biomarkers in Barrett's esophagus that could stratify patients with regards to neoplastic progression. We investigate the expression patterns of extracellular matrix (ECM) molecules in Barrett's esophagus and Barrett's esophagus-related neoplasia, and assess their value as biomarkers for the diagnosis of Barrett's esophagus-related neoplasia and to predict neoplastic progression. EXPERIMENTAL DESIGN: Gene-expression analyses of ECM matrisome gene sets were performed using publicly available data on human Barrett's esophagus, Barrett's esophagus-related dysplasia, esophageal adenocarcinoma (ADCA) and normal esophagus. Immunohistochemical expression of basement membrane (BM) marker agrin (AGRN) and p53 was analyzed in biopsies of Barrett's esophagus-related neoplasia from 321 patients in three independent cohorts. RESULTS: Differential gene-expression analysis revealed significant enrichment of ECM matrisome gene sets in dysplastic Barrett's esophagus and ADCA compared with controls. Loss of BM AGRN expression was observed in both Barrett's esophagus-related dysplasia and ADCA. The mean AGRN loss in Barrett's esophagus glands was significantly higher in Barrett's esophagus-related dysplasia and ADCA compared with non-dysplastic Barrett's esophagus (NDBE; P < 0.001; specificity = 82.2% and sensitivity = 96.4%). Loss of AGRN was significantly higher in NDBE samples from progressors compared with non-progressors (P < 0.001) and identified patients who progressed to advanced neoplasia with a specificity of 80.2% and sensitivity of 54.8%. Moreover, the combination of AGRN loss and abnormal p53 staining identified progression to Barrett's esophagus-related advanced neoplasia with a specificity and sensitivity of 86.5% and 58.7%. CONCLUSIONS: We highlight ECM changes during Barrett's esophagus progression to neoplasia. BM AGRN loss is a novel diagnostic biomarker that can identify patients with NDBE at increased risk of developing advanced neoplasia.

Cholangiolar pattern and albumin in situ hybridisation enable a diagnosis of intrahepatic cholangiocarcinoma.

AIMS: The histological distinction of intrahepatic cholangiocarcinoma (ICC) from metastatic adenocarcinoma remains a challenge. The primary goal was to evaluate the diagnostic value of morphology and albumin expression in the diagnosis of ICC. METHODS: We evaluated morphological patterns in 120 ICCs and 677 non-hepatic adenocarcinomas and performed in situ hybridisation (ISH) stain for albumin in the former cohort (retrospective cohort). We also identified 119 samples from primary and metastatic lesions, the validation cohort, in which albumin ISH was performed as part of the diagnostic workup. Targeted sequencing was performed on selected cases. We also mined existing expression profiling data including cases from The Cancer Genome Atlas (TCGA) (41 760 unique samples). RESULTS: In the retrospective cohort, 45% of ICCs and <1% of non-hepatic adenocarcinomas showed a cholangiolar pattern; albumin ISH was positive in 93% of ICCs with significant intratumorous heterogeneity. In the validation cohort, 29% of ICCs showed a cholangiolar pattern and 88% expressed albumin, while all metastatic non-hepatic neoplasms were negative (n=37) (sensitivity 88% and specificity 100%). Targetable genetic alterations (IDH mutations and FGFR2 fusions) were identified in 31% of ICCs (10 of 32). An analysis of the TCGA data validated the specificity of the albumin assay. CONCLUSIONS: The cholangiolar pattern and albumin RNA ISH distinguishes ICC from metastatic adenocarcinoma with high specificity. Given the high prevalence of targetable mutations in ICC, albumin RNA ISH is an essential component in the workup of tumours of uncertain origin. A specific diagnosis of ICC could trigger molecular testing and uncover targetable genetic alterations.

Agrin in the Muscularis Mucosa Serves as a Biomarker Distinguishing Hyperplastic Polyps from Sessile Serrated Lesions.

PURPOSE: Sessile serrated lesions (SSL) are precursors to colon carcinoma, and their distinction from other polyps, in particular hyperplastic polyps (HP), presents significant diagnostic challenges. We evaluated expression patterns in colonic polyps of previously identified colon carcinoma-associated extracellular matrix (ECM) proteins to identify markers distinguishing SSLs from other polyps. EXPERIMENTAL DESIGN: Gene-expression analyses of ECM proteins were performed using publicly available data on preneoplastic colonic polyps. In parallel, we evaluated by IHC the expression of agrin (AGRN) in over 400 colonic polyps, including HP, SSL with and without dysplasia, traditional serrated adenomas (TSA), and tubular adenomas (TA), and compared the consistency of standard histologic diagnosis of SSLs by experienced gastrointestinal pathologists with that of AGRN IHC. RESULTS: Differential gene expression analysis and IHC identified AGRN, serine peptidase inhibitor (SERPINE2), and TIMP metallopeptidase inhibitor 1 (TIMP1) elevated in SSLs and HPs but decreased in TAs and absent in normal colon. AGRN-positive basal laminae were noted in all TA, TSA, HP, and SSL in distinguishable patterns, whereas other polyps and normal mucosa were negative. SSL with or without dysplasia consistently showed IHC staining for AGRN in the muscularis mucosae, which was absent in HP, TSA, TA, and other polyps. In contrast, histologic evaluation showed only weak interobserver agreement (kappa value = 0.493) in distinguishing SSLs. CONCLUSIONS: Muscularis mucosae-based AGRN immunostaining is a novel biomarker to distinguish SSL from HP, TSA, and TA, with a specificity of 97.1% and sensitivity of 98.9% and can assist in diagnosis of morphologically challenging colonic polyps.

Microscopic colitis associated with omeprazole and esomeprazole exposure.

GOALS: The aim of this study was to determine whether proton pump inhibitors other than lansoprazole might be associated with microscopic colitis. BACKGROUND: Lansoprazole exposure has been associated with diarrhea and microscopic colitis, but this relationship has not been described with other proton pump inhibitors. STUDY: Cases of microscopic colitis from a consultative gastroenterology practice were collected and reviewed for proton pump inhibitor exposure. Standard clinical, endoscopic, and biopsy findings were analyzed. RESULTS: A case series of 4 patients is described in which subjects developed classic symptoms of lymphocytic-collagenous colitis with typical mucosal histopathology during treatment with omeprazole/esomeprazole. Symptoms promptly stopped and mucosal biopsies returned to normal with drug withdrawal. Disease quickly recurred in 2 patients who were reexposed to the drugs, one with biopsy documented recurrent collagenous colitis. CONCLUSIONS: Some cases of microscopic colitis seem to be associated with omeprazole/esomaprazole exposure. These results have epidemiologic, diagnostic, and therapeutic ramifications, which are discussed.

Vascular Injury Characterizes Doxycycline-induced Upper Gastrointestinal Tract Mucosal Injury.

Doxycycline is an oral tetracycline antibiotic that has been associated with upper gastrointestinal (GI) mucosal injury. Recently, characteristic vascular degeneration has been reported in the stomach and duodenum in patients with doxycycline-induced injury. Fourteen patients who underwent upper GI endoscopy for nonspecific symptoms and were found to have doxycycline-induced gastric and esophageal injury are described. Most patients showed characteristic vascular injury. A control group of gastric erosions and esophageal ulcers showed no cases with the characteristic vascular changes. Clinical, endoscopic, and pathologic features of doxycycline-induced upper GI tract injury are reviewed, with an emphasis on vascular injury.

Hepatic capillariasis in Maine presenting as a hepatic mass.

We report the first case of hepatic capillariasis in Maine. The patient was a 54-year-old male carpenter who presented with a subacute history of severe abdominal pain, fevers, and weight loss. Initial diagnostic studies suggested a hepatic mass associated with para-aortic lymphadenopathy. The patient underwent open laparotomy for resection of the mass. He was found to have an eosinophilic granuloma in the liver; further evaluation revealed degenerating Capillaria hepatica. The exact route of infection in this case is unknown but is most likely due to accidental ingestion of soil contaminated with mature capillaria eggs. This patient had a low parasite burden and did not exhibit significant peripheral eosinophilia. After treatment with thiabendazole, he recovered uneventfully.

Appropriate use of special stains for identifying Helicobacter pylori: Recommendations from the Rodger C. Haggitt Gastrointestinal Pathology Society.

Helicobacter pylori is a major cause of gastroduodenal injury, gastric cancer, and lymphoma, and, thus, there is great interest in its detection and eradication. Several detection methods are available, including histochemical and immunohistochemical stains. Application of these stains in clinical practice is heterogenous, to say the least. Although they were developed to enhance H. pylori detection, changing practice models, financial considerations, and a perceived need for rapid case turnaround have led to their widespread use in routine staining studies ordered reflexively on all gastric biopsies. Emerging data suggest that most of these stains are not needed to establish a diagnosis of H. pylori infection, and their added value when biopsies show minimal, or no, inflammation is not clear. In this manuscript, the Rodger C. Haggitt Gastrointestinal Pathology Society puts forth recommendations regarding ancillary stain usage for H. pylori detection based upon critical literature review and collective experience. Pathologists rarely, if ever, detect H. pylori in "normal" biopsies, but readily observe them in optimally stained hematoxylin and eosin sections from infected patients. Therefore, we suggest that use of ancillary stains is appropriate when biopsies show chronic, or chronic active, gastritis without detectable H. pylori in hematoxylin and eosin-stained sections, but performing them "up front" on all gastric biopsies is generally unnecessary. Application of these stains to nongastric biopsies and polyps is appropriate in an extremely limited set of circumstances. It is our hope that recommendations provided herein will provide helpful information to gastroenterologists, pathologists, and others involved in the evaluation of patients for possible H. pylori infection.

Celiac sprue, hyperhomocysteinemia, and MTHFR gene variants.

GOALS: To describe the association of untreated celiac disease with hyperhomocysteinemia and variants of the methylenetetrahydrofolicacid reductase (MTHFR) gene found in clinical practice. STUDY: Case studies with description of associated clinical, biochemical, and genetic findings and review of literature. RESULTS: Five new cases and 7 additional cases found from literature search of hyperhomocysteinemia with celiac sprue are reported. Treatment with gluten-free diet and folic acid led to the variable improvement in homocysteine levels. MTHFR gene variants were present in the each of the new patients described. CONCLUSIONS: Untreated celiac disease may be associated with hyperhomocysteinemia caused by a combination of vitamin deficiencies and variants in the MTHFR gene. Abnormalities do not consistently improve with gluten-free diet. The abnormal findings could result from vitamin deficiencies or variant MTHFR status. Possible clinical implications for patients with celiac disease and hyperhomocysteinemia are reviewed.

Success and complications of endoscopic removal of giant duodenal and ampullary polyps: a comparative series.

BACKGROUND: Increasing reports suggest that endoscopic removal of benign ampullary and duodenal polyps is safe and frequently definitive; however, most reported polyps have been small in size (<3 cm). We have developed experience with endoscopic removal of increasingly large and complex polyps. PATIENTS: Fifty-one cases of endoscopic removal were attempted and grouped according to size: group A (n = 22) polyps 1 to 3 cm and group B (n = 29) polyps 3 cm or larger, including 7 cases larger than 5 cm. When the ampulla was involved, biductal sphincterotomy and prophylactic pancreatic duct stent placement was performed first, followed by saline solution-assisted piecemeal polypectomy, argon plasma coagulation, selective endoclip placement, and recovery of all polyp fragments. INTERVENTIONS: Endoscopic removal of duodenal and ampullary adenomas. RESULTS: The outcomes of small and large adenoma removal include mean number of endoscopic retrograde cholangiopancreatographies required for complete removal (2.09 vs 2.56, P = .392), number of complications (4.5% vs 13.9%, P = .375), discovery of unsuspected cancer (0% vs 10.3%, P = .242), and final definitive resolution (100% vs 86.2%, P = .124). Complete removal was achieved in 92.2% of all patients. LIMITATIONS: This was a single center retrospective study. CONCLUSIONS: Large (>/=3 cm) ampullary and duodenal polyps comprised 56.9% of our endoscopically treated cases and present special challenges to definitive endoscopic removal. Successful removal of even very large sessile lesions is possible with minimal increase in risk.

Rofecoxib and inflammatory bowel disease: clinical and pathologic observations.

OBJECTIVES: To describe clinical and pathologic findings in patients noted to develop lower gastrointestinal symptoms when exposed to rofecoxib. METHODS: Case reports and associated biopsy findings. RESULTS: Three patients who developed symptoms of inflammatory bowel disease (IBD) during rofecoxib exposure are described along with pathology findings. Two episodes were incident cases (no prior IBD); one episode was recurrent colitis or a nonincident case (flare of prior IBD). All symptoms resolved with drug withdrawal. CONCLUSIONS: Symptoms and pathologic changes of colitis are associated with exposure to rofecoxib. Abnormalities resolve with drug withdrawal.

Collagenous colitis associated with lansoprazole.

BACKGROUND: Collagenous colitis is a diarrheal illness of unknown cause. The purpose of this report is to describe a case of collagenous colitis related to lansoprazole exposure. STUDY: Case report. RESULTS: A patient is described who developed clinical and pathologic findings of collagenous colitis during treatment with lansoprazole and omeprazole. Symptoms of diarrhea and histopathologic abnormalities resolved after drug withdrawal and recurred with re-exposure to lansoprazole. CONCLUSIONS: The observations are compatible with collagenous colitis or lymphocytic colitis associated with exposure to lansoprazole.