Lymphocytic colitis pattern of injury presenting as endoscopic polyps: a case series

Clinical Implications of Microscopic Colitis Isolated to Polyps

Microscopic colitis is generally identified on random colon biopsies performed for chronic diarrhea, but rarely incidental polyps have histologic features of microscopic colitis. We compared patients with polypoid microscopic colitis to control patients with conventional polyps to determine the implications of polypoid microscopic colitis.

Medical records were searched for patients without prior or concurrent microscopic colitis who were found to have polypoid microscopic colitis. For each patient with polypoid microscopic colitis, one patient with conventional polyps was selected as a control. We reviewed the histologic features of each polypoid microscopic colitis specimen, and evaluated endoscopic and clinical findings for polypoid microscopic colitis patients and controls.

Twenty-six patients with polypoid microscopic colitis were identified with histologic features of collagenous colitis in 8 patients (31%) and lymphocytic colitis in 18 patients (69%). Polypoid microscopic colitis was unifocal in 14 patients (54%) and multifocal in 12 patients (46%). Patients with polypoid microscopic colitis were older than control patients (median age = 60 years vs 66 years, P = .04). On follow-up 7 patients with polypoid microscopic colitis (33%) developed chronic diarrhea compared to 3 (12%) controls (P = .16). Of patients with follow-up biopsies, 1 patient with polypoid microscopic colitis (13%) and no control patients developed microscopic colitis (P = 1).

Polypoid microscopic colitis may be identified in asymptomatic patients and most patients do not develop chronic diarrhea, but some patients with polypoid microscopic colitis develop diarrhea (33% vs 12% in controls) or conventional microscopic colitis on follow-up. Thus pathologists should distinguish polypoid microscopic colitis from conventional microscopic colitis but may inform clinicians of the uncertain association with chronic diarrhea to guide decisions regarding follow-up.

Histologic Findings and Tissue B-Cell Depletion in Endoscopic Mucosal Biopsy Specimens of the Gastrointestinal Tract After Treatment With Rituximab

OBJECTIVES

Rituximab (RTX) is associated with variable adverse gastrointestinal (GI) events. However, the histologic correlate in affected patients is not well defined.

METHODS

Patients (n = 93) who had received RTX and undergone endoscopic biopsies were identified. CD20 and PAX5 immunostains were performed on biopsy specimens showing inflammatory pathology (group A, 36 patients) and 35 of 57 noninflammatory biopsies (group B) that were taken within 1 year from the last RTX infusion. Histologic findings were correlated with tissue B-cell depletion (CD20/PAX5-/-).

RESULTS

B cells were depleted in 12 (33%) of 36 group A biopsy specimens. After excluding biopsies taken more than 1 year from the last RTX infusion, the frequencies of tissue B-cell depletion were similar between group A (12/26; 46.2%) and group B (17/35; 48.6%) (P > .05). Also, the frequencies of inflammatory pathology were not statistically different whether B cells were depleted or not (P > .05). In group A with tissue B-cell depletion (n = 12), causality was indicated in two (17%) cases showing lymphocytic colitis pattern of injury (LCPI).

CONCLUSIONS

In RTX-treated patients, tissue B-cell depletion does not appear to be the main cause of inflammatory pathology in the GI tract. A minor subset, however, develops histologic evidence of potential RTX-induced effect, notably in the form of LCPI.