Have been diagnosed with ovarian cancer, what are the chances that this was hereditary?

Low chance: Without a family history of breast or ovarian cancer, a single case of ovarian cancer has a low risk to be caused by a single gene mutation (e.g., the brca1 or brca2 mutations). However, testing for brca can be considered with an isolated case of ovarian cancer, particularly if it is in a women under 45 or the woman has children who would be at 50% risk of inheriting a brca mutation.

About 8.5%: Less then 10% of ovarian cancers are currently known to arise from inherited mutations.