A 60-year-old woman underwent laparoscopic pyloric gastrectomy for advanced gastric cancer. Colonoscopy was performed for post-surgical surveillance thirty months later.
Colonoscopy showed a 10-mm flat lesion in the transverse colon.
Endocytoscopy of the lesion revealed glandular ductal openings that were clearly smaller than those in the surrounding normal mucosa. There was a cluster of mildly enlarged nuclei, stained darkly with methylene blue, around the gland duct orifices. The colorectal lesion was resected.
Immunohistological examination of the resected lesion revealed positivity for MUC5AC in shallow layers, and positivity for MUC6 in deep layers. This is similar to the distribution in gastric mucosa.
The mucus traits mimicked those of the epithelium of the gastric fossa, and other immunostains were consistent with gastric cancer. The final pathological diagnosis was poorly differentiated adenocarcinoma in the colonic mucosa compatible with metastatic gastric cancer.
