SIGNET-RING CELL AGGREGATES SIMULATING CARCINOMA IN COLON AND GALLBLADDER MUCOSA

We describe three cases of benign signer-ring cell aggregates in the c olon associated with pseudomembranous colitis, adenomatous polyp of th e colon and ulcerated mucosa of the gallbladder excised for gallstones . In all cases, we found loose, benign signet-ring cell aggregates ove rlying the ulcerated mucosa surface, simulating signet ring-cell carci noma. The most important sign of the benign signet-ring cell aggregate s is that they are always confined to the surface of the mucosa of the intestine or gallbladder mucosa or crypts of the intestinal epitheliu m. In no case did we see an invasion of these cells into the lamina pr opria of the mucosa. In all cases, the benign signet-ring cell aggrega tes were immunohistochemically positive with antibodies to cytokeratin s. The occurrence of benign signet-ring cell aggregates is a rare and very misleading diagnostic pitfall which must be differentiated from s igner-ring cell carcinoma of the colon and gallbladder.