LAUSR

OBJECTIVE Mucinous borderline ovarian tumor (mucinous-BOT) and invasive well-differentiated mucinous ovarian cancer (mucinous-OC) are often histopathologically misclassified. The objective of this study was to examine differences in clinico-pathological characteristics and outcomes of these two entities. METHODS This is a retrospective population-based study examining the Surveillance, Epidemiology, and End Results Program from 1988 to 2000. Stage I mucinous-BOTs and stage I well-differentiated mucinous-OC were compared for patient demographics, tumor characteristics, and outcomes. Propensity score matching and multivariable analysis were used to assess cause-specific survival (CSS). RESULTS A total of 2130 mucinous-BOT and 581 mucinous-OC cases were examined for analysis. On multivariable analysis, women with mucinous-OC were more likely to be older, Eastern U.S. residents, and have undergone hysterectomy or lymphadenectomy compared to those with mucinous-BOT, and the number of women diagnosed with mucinous-OC decreased over time (all, P < 0.05). Mucinous-OCs were more likely to be stage T1c and have a smaller tumor size as compared to mucinous-BOT (both, adjusted-P < 0.05). After propensity score matching, women with mucinous-OC had significantly poorer CSS compared to those with mucinous-BOT on multivariable analysis (10-year rates: 92.7% versus 97.5%, adjusted-hazard ratio [HR] 2.03, P = 0.007). Similar results were observed among subgroups for reproductive age, stage T1a disease, large tumor, and unstaged cases (all, P < 0.05). CONCLUSION Stage I mucinous-BOT and stage I invasive well-differentiated mucinous-OC have distinct differences in clinical characteristics and patient survival. The inability to conduct centralized pathology review in our study limits our conclusions given the recognized issue of misclassification of mucinous-BOT and mucinous-OC, but further highlights the importance of making the proper histopathological diagnosis for invasive cancer when the ovarian tumor is of mucinous histology.