Endometrioid Carcinoma of the Uterine Corpus With a Micropapillary Component: A Novel Prognostic Factor For Metastasis.

Background/aimMicropapillary pattern is a morphologically distinctive form of carcinoma composed of small, hollow, or morula-like clusters of cancer cells surrounded by clear stromal spaces. The neoplastic cells characteristically display a reverse polarity, also known as an ''inside-out'' growth pattern, that is linked to higher frequencies of lymphovascular invasion and lymph nodal metastasis. To the best of our knowledge, it has not been previously recognized in uterine corpus.Case reportWe report 2 cases of endometrioid carcinoma of the uterine corpus with a micropapillary component. In these cases, histological examination identified an endometrioid carcinoma that had invaded the myometrial layer. The carcinoma cells that constructed the micropapillary components were immunohistochemically positive for EMA. They lined the stromal facing surface of the cell membrane, confirming the inside-out growth pattern, and D2-40 immunohistochemistry confirmed lymphovascular invasion of carcinoma cells.ConclusionWe believe that the micropapillary pattern linked to higher frequencies of lymphovascular invasion and lymph nodal metastasis may be one of the most important invasive patterns in endometrioid carcinomas of the uterine corpus for predicting aggressive malignant potential, prognosis, and recurrence, although further, larger studies are required to evaluate its clinical significance.