Background: A mortality benefit from screening for OVCA has not been demonstrated, but screening efficacy could differ for histologic subtypes. We re-analyzed PLCO evaluating whether OVCA detection and outcomes were affected by the heterogeneous biologic behavior of this disease. Methods: Type 2 tumors (moderately/poorly differentiated serous and adenocarcinoma) were compared to all other tumor (OT) types (low grade serous and endometrioid, clear cell, other, low malignancy potential) (LMP). We examined differences in the distribution of tumor types and stage by study arm and method of diagnosis [screen detected (SD) and interval detected (ID) (i.e. assigned to screening but diagnosed between screening tests)]. Stage distribution and survival were analyzed. Results: Among the entire PLCO population, 531 women were diagnosed with OVCA during the study; 282 (53%) in the screening arm and 249 (47%) in the usual care arm. Of the tumors able to be characterized (n=408; 77%), 74% (n=300) were Type 2 and 26% OT (n=108). In the screening arm, 70% of tumors diagnosed were Type 2 compared to 78% in usual care (p=0.07). Overall, survival was significantly better for OT tumors compared to Type 2 tumors (p<0.01) but there was no difference in survival by study arm for either tumor type separately (Type 2: p=0.50; OT: p=0.23). Within the screening arm, 30% of Type 2 tumors were SD compared to 54% of OT tumors (p=0.02) (see Table). Only 15% of Type 2 SD tumors were Stage I/II, compared to 82% of SD OT tumors (p<0.01). Stage at diagnosis was similar among Type 2 patients whether they were SD or ID (p=0.56) and there was no difference in survival (p=0.56). Conclusions: A significant difference in tumor types by study arm was not observed. However, within the screening arm, Type 2 tumors were less likely to be SD or Stage I/II compared to OT tumors. Survival for Type 2 tumors was similar regardless of method of diagnosis.