Pure compared with mixed serous endometrial carcinoma: two different entities?

ABSTRACT

OBJECTIVE: To analyze whether mixed compared with pure uterine papillary serous carcinoma histology affects clinical outcome, and to assess uterine papillary serous carcinoma for its association with the precursor lesion endometrial intraepithelial carcinoma. METHODS: A multi-institution observational study of stage I-IV uterine papillary serous carcinoma patients was performed. Histopathologic slides were reviewed by four expert pathologists, with determination of the percentage serous histology within each tumor. The pre-existent endometrium was evaluated for the presence of endometrial intraepithelial carcinoma. RESULTS: We included 108 uterine papillary serous carcinoma patients. Fifty-eight patients had mixed and 50 patients had pure uterine papillary serous carcinoma histology. On multivariable analysis, advanced International Federation of Gynecology and Obstetrics (FIGO) stage (hazard ratio [HR] 3.15, 95% confidence interval [CI] 1.57-6.32), mixed uterine papillary serous carcinoma histology (HR 0.35, 95% CI 0.19-0.66), and lymphovascular space invasion (HR 2.10, 95% CI 1.07-4.16) were significantly associated with recurrence. International Federation of Gynecology and Obstetrics stage (HR 4.67, 95% CI 2.25-9.70) and mixed uterine papillary serous carcinoma histology (HR 0.39, 95% CI 0.20-0.76) were significantly and independently associated with survival. Endometrial intraepithelial carcinoma was identified in 83.9% of all cases, with no significant difference between mixed and pure uterine papillary serous carcinoma patients. Atrophic or weakly proliferative endometrium was found in 90.7% of pure uterine papillary serous carcinoma cases, whereas hyperplastic endometrium with atypia was more commonly found in 34.7% of mixed carcinoma patients with uterine papillary serous carcinoma (P=.004). CONCLUSION: Pure uterine papillary serous carcinoma histology and FIGO stage are the most important risk factors for recurrence and survival in patients with uterine papillary serous carcinoma. Adjusted for covariates, patients with pure uterine papillary serous carcinoma had a 2.9-times greater risk for recurrence and a 2.6-times higher risk of death compared with patients with mixed uterine papillary serous carcinoma. Furthermore, endometrial intraepithelial carcinoma was equally found among pure and mixed uterine papillary serous carcinoma cases, whereas the nonneoplastic endometrium was atrophic or weakly proliferative in pure uterine papillary serous carcinoma cases compared with more hyperplastic endometrium with atypia in mixed uterine papillary serous carcinoma cases.