Differences in tumor type in low-stage versus high-stage ovarian carcinomas.

Although there are recognized differences in the type of ovarian carcinomas between those tumors diagnosed at low versus high stage, there is a lack of data on stage distribution of ovarian carcinomas diagnosed according to the current histopathologic criteria from large population-based cohorts. We reviewed full slide sets of 1009 cases of 2555 patients diagnosed with ovarian carcinoma that were referred to the British Columbia Cancer Agency over a 16-year period (1984 to 2000). On the basis of the reviewed cases we extrapolated the distribution of tumor type in low-stage (I/II) and high-stage (III/IV) tumors. We then compared the frequencies with those seen in a large hospital practice. The overall frequency of tumor types was as follows: high-grade serous-68.1%, clear-cell-12.2%, endometrioid-11.3%, mucinous-3.4%, low-grade serous-3.4%, rare types-1.6%. High-grade serous carcinomas accounted for 35.5% of stage I/II tumors and 87.7% of stage III/IV tumors. In contrast, clear-cell (26.2% vs. 4.5%), endometrioid (26.6% vs. 2.5%), and mucinous (7.5% vs. 1.2%) carcinomas were relatively more common among the low-stage versus high-stage tumors. This distribution was found to be very similar in 410 consecutive cases from the Washington Hospital Center. The distribution of ovarian carcinoma types differs significantly in patients with low-stage versus high-stage ovarian carcinoma when contemporary diagnostic criteria are used, with consistent results seen in 2 independent case series. These findings reflect important biological differences in the behavior of the major tumor types, with important clinical implications.