Co-immunofluorescence (IF) was performed in a previously described cohort of 200 HGSC on tissue microarray (TMA)9 (link) and in a previously described cohort of 1000 HGSC (from the Canadian Ovarian Experimental Unified Resource)25 (link) on TMA (online supplemental table S1). Only cases that did not receive neoadjuvant chemotherapy were included for analyses. Slides were deparaffinized, rehydrated, demasked using a citrate buffer and incubated for 30 min with a protein blocking solution. Primary antibodies were co-incubated on the slides overnight at 4°C and secondary antibodies were incubated for 2 hours at room temperature (online supplemental table S2). Slides were then mounted with 4′,6-diamidino-2-phenylindole (DAPI). Sections were imaged at 20X magnification on VS-110 scanner (Olympus) and super images were imported into Visiomorph DP (Visiopharm). CK8-18 positivity was used to identify the epithelial area and where indicated α smooth muscle actin (SMA) positivity was used to identify the activated stromal area. Cores with epithelial or stromal areas representing less than 5% of the total tissue area were eliminated from survival analyses. Recommendations for Tumor Marker Prognostic Studies criteria were followed.26 (link)