BRCA1 and myeloproliferative neoplasm: Considering that BRCA1 mutations in patients with familial MPN extend beyond the bone marrow, data from triple-negative breast and ovarian cancer patients harboring heterozygous germline BRCA1 mutations who have undergone olaparib treatment might aid in estimating treatment-associated side effects on BRCA1-haploinsufficient non-cancerous cells.