Whereas type 1 tumors are typically preceded by endometrial hyperplasia and are associated with a loss of PTEN expression as well as abnormalities in β-catenin, Kras, and DNA mismatch repair genes, type 2 tumors represent a heterogeneous group of tumors including high-grade (undifferentiated) endometrioid carcinomas, uterine papillary serous carcinomas, clear cell carcinomas, and carcinosarcomas. The gene discussed is PTEN; the disease is endometrial serous adenocarcinoma.