Endometrial Gastrointestinal Mucinous Metaplasia With Goblet Cells and KRAS Mutation-Report of Two Patients and Review of Literature.

Mucinous metaplasia in benign and malignant endometrial entities is well recognized. The mucinous epithelium may resemble the endocervix, coined as "usual mucinous metaplasia," or may be gastric type epithelium consisting of bland epithelium with abundant pale cytoplasm, with or without goblet cells, so-called "gastrointestinal metaplasia." Mostly described in premalignant and malignant endometrial entities (endometrial intraepithelial neoplasia/atypical hyperplasia and carcinoma), rare examples of gastrointestinal metaplasia arising in benign endometrial polyps have been reported. In this paper, we report two additional postmenopausal patients with endometrial polyps showing gastrointestinal metaplasia with goblet cells. We performed molecular analysis, which revealed KRAS mutation in codons 12/13 in the first patient and codon 61 in the second patient. These associations raise the possibility that KRAS mutations could be an early event in the endometrial carcinogenesis pathway, and that simple mucinous metaplasia of gastrointestinal type may represent an early precursor lesion.