The presence of an endometrioid component does not alter the clinicopathologic profile or survival of patients with uterine serous cancer: A gynecologic oncology group (GOG/NRG) study of 934 women

Objective: While most cases of endometrial cancer can readily be classified as pure endometrioid, pure serous, or another type, others show an apparent mixture of serous and endometrioid components, or indeterminate serous versus endometrioid features. Since serous histology carries a worse prognosis than endometrioid, Gynecologic Oncology Group protocol GOG-8032 was established to examine whether the presence of a non-serous component is a favorable feature in an otherwise serous cancer. Methods: 934 women with serous cancer were prospectively identified among a larger group enrolled in GOG-0210. Six expert gynecologic pathologists classified each case as pure serous (SER, n=663), mixed serous and endometrioid (SER-EM-M, n=138), or indeterminate serous v. endometrioid (SER-EM-I, n=133) by H&E morphology. Follow-up data from GOG-0210 were analyzed. Results: The subgroups did not differ on BMI, race, ethnicity, lymphovascular invasion, cervical invasion, ovary involvement, peritoneal involvement, omental involvement, FIGO stage, or planned adjuvant treatment. SER-EM-M patients were younger (p=0.0001) and less likely to have nodal involvement (p=0.0287). SER patients were less likely to have myoinvasion (p=0.0002), and more likely to have adnexal involvement (p=0.0108). On univariate analysis, age, serous subtype, race, and components of FIGO staging predicted both progression-free and overall survival. On multiple regression, however, serous subtype (SER, SER-EM-M, or SER-EM-I) did not significantly predict survival. Conclusions: There were few clinicopathologic differences between cases classified as SER, SER-EM-M, and SER-EM-I. Cases with a mixture of serous and endometrioid morphology, as well as cases with morphology indeterminate for serous v. endometrioid type, had the same survival as pure serous cases.