Clinicopathological characteristics and KRAS mutation status of endometrial mucinous metaplasia and carcinoma

Background/Aim: Mucinous metaplasia of the endometrium occurs as a spectrum of epithelial alterations ranging from the formation of simple, tubular glands to architecturally complex glandular proliferation with intraglandular papillary projection and cellular tufts. Endometrial mucinous metaplasia often presents a diagnostic challenge in endometrial curettage. Materials and Methods: We analyzed the clinicopathological characteristics and the mutation status for V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) of 11 cases of endometrial mucinous metaplasia. Electronic medical record review and histopathological examination were performed. KRAS mutation status was analyzed using a pyrosequencing technique. Results: Cases were classified histopathologically into simple (5/11) or papillary (6/11) mucinous metaplasias. All (6/6) papillary mucinous metaplasias were associated with atypical hyperplasia/endometrioid intraepithelial neoplasia (AH/EIN; 1/6) or carcinoma (5/6), whereas in a single patient with simple mucinous metaplasia, grade 1 endometrioid carcinoma was incidentally detected. The difference in frequency of association of the metaplasia with AH/EIN or carcinoma was significant (p=0.015). KRAS mutations were identified in five out of six cases of papillary mucinous metaplasias, comprising three cases with G12D and two with G12V mutations; the frequency of KRAS mutation was significantly higher (p=0.015) than in cases of simple mucinous metaplasia (0/5). Conclusion: Papillary mucinous metaplasia is frequently associated with endometrial neoplastic lesions. The high incidence of KRAS mutations in papillary mucinous metaplasia suggests that papillary mucinous metaplasia may be a precancerous lesion of a certain subset of mucinous carcinomas of the endometrium.