Extruded Highly Proliferative Benign Mucous Neck Cells

Abstract

Histologic mimics of poorly cohesive gastric carcinoma are uncommon but are important for pathologists to recognize. Here we report 2 cases of a novel histologic pattern mimicking poorly cohesive gastric carcinoma. In both cases, light microscopy revealed sheets of discohesive epithelial cells with prominent mitoses that have high proliferative activity, with a Ki67 proliferation index greater than 70%. One case was diagnosed as poorly cohesive carcinoma at an outside hospital and the other was referred in consultation as atypia of undetermined significance. Reexamination of the hematoxylin–eosin slides revealed morphologic clues that these sheets of discohesive cells represent artifactual extrusion of the highly proliferative neck zone from the surrounding benign mucosa. In contrast to poorly cohesive cancer, this artifact lacks all of the following diagnostic features: nuclear atypia, signet ring cell morphology, and intercellular stroma with infiltrating single cells between glands. Eight and 14 months later, both patients remain cancer free.