Shafrir AL, Babic A, Kuliszewski MG, et al. - In view of the differential associations between ovarian cancer risk factors and estrogen receptor-α (ERα) ovarian tumor expression, researchers performed exploratory analyses investigating the correlation of several factors with ovarian cancer risk by ERβ tumor status. A nested case–control study was performed within the prospective Nurses’ Health Study cohorts (NHS/NHSII), with exposures obtained through biennial questionnaires. For cases diagnosed from 1976 to 2006 (NHS) and 1989 to 2005 (NHSII), paraffin-embedded tumor blocks were requested and staining of tissue microarrays was done for nuclear ERβ (ERβ-nuc) and cytoplasmic ERβ (ERβ-cyto), with any staining considered positive (+). Inclusion of 245 cases [43% ERβ-cyto (+) and 71% ERβ-nuc (+)] and 1,050 matched controls was performed. Parity had an inverse association with the risk of ERβ-nuc (+), but not ERβ-nuc (–) tumors. Conversely, an inverse association of parity with ERβ-cyto (–) tumors was observed, but it showed no association with ERβ-cyto (+) tumors. Per these findings, through alterations in ERβ localization within tumor cells, parity, in part, may influence ovarian cancer risk.