BRCA1 and ovarian carcinoma: This observation cannot be solely explained by an earlier occurrence of a "second hit" as modeled by Knudson's two-hit hypothesis [7] because the age of presentation of ovarian cancer in BRCA2 tumors is no different than that observed in patients with sporadic epithelial ovarian cancers [2,6], thus indicating a BRCA1-specific effect on the age of presentation.