Morules in epithelial tumors of the colon and rectum.

Eighteen colorectal adenomas and an invasive carcinoma containing epithelial aggregates similar to the morules which have been described in endometrium are presented and their histopathologic features and significance considered. These structures protruded into the lumina of the neoplastic tubules and were composed of cytologically bland cells in a syncytial-like arrangement with a solid or fenestrated pattern. As in endometrium, they appear to represent a peculiar metaplasia and should not influence the assessment for carcinoma; it should be based on the glandular component of the tumor.