In this chapter, we review high-grade endometrial carcinoma subtypes including FIGO grade 3 endometrioid carcinoma, serous carcinoma, clear cell carcinoma, undifferentiated/dedifferentiated carcinoma, neuroendocrine carcinoma, carcinosarcoma, mesonephric-like carcinoma, and carcinoma with somatically derived yolk sac tumor. We discuss the clinical and histomorphologic features of these entities as well as the ancillary tests that can contribute to their diagnosis.