Endometrial Carcinomas with Intestinal-Type Metaplasia/Differentiation: Does Mismatch Repair System Defects Matter? Case Report and Systematic Review of the Literature

Background: Intestinal metaplasia/differentiation in primary endometrial carcinomas is an uncommon phenomenon, with only few cases described. Material and Methods: We performed a systematic review of endometrial carcinomas with intestinal metaplasia/differentiation interrogating the electronic databases Pubmed, Web of Science, and Scopus, and we reported an additional case arising in a 49-year-old woman. Results: We identified only eight patients diagnosed with endometrial carcinomas exhibiting intestinal metaplasia/differentiation, and additionally our case. Endometrial carcinomas with intestinal-type features can present in pure or mixed forms in association with usual-type endometrioid carcinomas; in mixed forms, the two neoplastic components may derive from a common neoplastic progenitor, as evidenced by the concomitant loss of MSH2 and MSH6 protein expression in our case. Disease recurrences occur in a significant fraction of the cases, including patients diagnosed in low-stage disease. Conclusions: Endometrial carcinomas with intestinal metaplasia/differentiation are rare and they may represent a more aggressive tumor variant, thus requiring a proper treatment despite the low-tumor stage. The ProMise classification should be performed also in these unusual tumors, since they can be associated with mismatch repair system defects.