The surface epithelium is infiltrated by numerous lymphocytes. Furthermore, the subepithelial collagen layer is enlarged, but does not meet the criteria for a collagen colitis yet.Clinical features:chronic, watery diarrhea: Collagen colitis? Lymphocytic colitis?Comment:Overall the features of a lymphocytic colitis predominate in the available biopsies with an increase in intraepithelial lymphocytes to as much as 90 lymphocytes per 100 epithelial cells (normally 20 per 100 epithelial cells). In left-sided biopsies of the colon a focal thickening of the subepithelial collagen layer to as much as 10 micrometer can be found.Staining: Van GiesonSource: © PathoPic