A binary histologic grading system for ovarian serous carcinoma is an independent prognostic factor: a population-based study of 4317 women diagnosed in Denmark 1978-2006.

OBJECTIVE

To evaluate the prognostic significance of histologic grade on survival of ovarian serous cancer in Denmark during nearly 30 years.

METHODS

Using the nationwide Danish Pathology Data Bank, we evaluated 4317 women with ovarian serous carcinoma in 1978-2006. All pathology reports were scrutinized and tumors classified as either low-grade serous carcinomas (LGSC) or high-grade serous carcinomas (HGSC). Tumors in which the original pathology reports were described as well-differentiated were classified as LGSC, and those that were described as moderately or poorly differentiated were classified as HGSC. We obtained histologic slides from the pathology departments for women with a diagnosis of well-differentiated serous carcinoma during 1997-2006, which were then reviewed by expert gynecologic pathologists. Data were analyzed using Kaplan-Meier methods and Cox proportional hazards regression analysis with follow-up through June 2009.

RESULTS

Women with HGSC had a significantly increased risk of dying (HR=1.9; 95% CI: 1.6-2.3) compared with women with LGSC while adjusting for age and stage. Expert review of 171 women originally classified as well-differentiated in 1997-2006 were interpreted as LGSC in 30% of cases, whereas 12% were interpreted as HGSC and 50% as serous borderline ovarian tumors (SBT). Compared with women with confirmed LGSC, women with SBT at review had a significantly lower risk of dying (HR=0.5; 95% CI: 0.22-0.99), and women with HGSC at review had a non-significantly increased risk of dying (HR=1.6; 95% CI: 0.7-3.4).

CONCLUSIONS

A binary grading system is a significant predictor of survival for ovarian serous carcinoma.