The diagnosis of microscopic colitis MC is made by histologic evaluation of colonic biopsies; the classic finding is intraepithelial lymphocytosis (>20 intraepithelial lymphocytes per 100 epithelial cells). In collagenous colitis, the increase in intraepithelial lymphocytes may be less pronounced than in lymphocytic colitis, and the main histologic feature is thickening of the subepithelial collagen band (usually >10 µm)