Immune checkpoint inhibitor (anti PD-1/PD-L1 antibody activity in dedifferentiated endometrial carcinoma.

e17565Background: Dedifferentiated endometrial carcinoma is defined as the undifferentiated carcinoma admixed with well-differentiated endometrioid carcinoma (Grade 1 or 2). Dedifferentiated endometrial carcinoma has a poor prognosis as compared with endometrioid adenocarcinoma of Grade 3, but it is often associated with loss of mismatch repair (MMR) proteins, which seen in microsatellite instability (MSI) type endometrial cancer with good prognosis. In recent study, effectiveness of immune checkpoint inhibitor therapy is related to loss of MMR proteins, so we examined the loss of MMR proteins proteins and the expression of PD-1 / PD-L1 in dedifferentiated endometrial carcinoma. Methods: Expression of MMR proteins (MLH1, PMS2, MSH2, and MSH6), CD8, PD-L1, and PD-1 were evaluated by immunohistochemistry in 17 cases of dedifferentiated endometrial carcinoma. Results: Since the undifferentiated region and the well-differentiated region showed different staining results, we evaluated them separately. In the u...