Carpet-Like Polypoid Lesion in Collagenous Colitis with Mucosal Giant Cells

Departments of Medicine (Gastroenterology) and Pathology, University of British Columbia, Vancouver, British Columbia Correspondence: Dr Hugh James Freeman, University of British Columbia Hospital, 2211 Wesbrook Mall, Vancouver, British Columbia V6T 1W5. Telephone 604-822-7216, fax 604-822-7236, e-mail hugfree@shaw.ca Received for publication April 4, 2010. Accepted April 14, 2010 Case presentation and images A 78-year-old woman experienced intermittent watery diarrhea for more than one year. There was no previous antibiotic use, travel or other medical history. The physical examination was normal. Laboratory studies, including bloodwork and fecal cultures, were negative. Colonoscopy revealed sigmoid diverticulosis and a broad-based sessile, ‘carpet-like’ polypoid lesion at the hepatic flexure appearing to occupy approximately 40% to 50% of the colonic circumference; consequently, the lesion was biopsied only (Figure 1) and ink-tattooed (for later laparoscopic removal). Biopsy sections (Figures 2 and 3) showed collagenous colitis with thickening of the basal collagen plate, an irregular lower border, entrapped nuclei, loss of overlying surface epithelium and increased inflammatory cells in the lamina propria. Subepithelial multinucleated giant cells were present (arrows). A trichrome stain highlighted the thickened basal collagen plate with entrapped nuclei (Figure 4). Over the next few weeks, her diarrhea completely resolved on a high-fibre diet regimen alone.