Hereditary Breast Cancer in South Sweden. Early findings from studies on the role of BRCA1

Abstract: The thesis presents the results from investigations into the role of BRCA1 in hereditary cancer in South Sweden. Loss of heterozygosity (LOH) studies found loss of the wildtype allele of BRCA1 to be common in BRCA1 associated breast cancer, but due to the high degree of LOH on chr. 17q in sporadic breast cancer not to be indicative of the presence of a BRCA1 mutation. Seventeen different germline BRCA1 mutations have been found in 34 separate breast and breast-ovarian cancer families. Five founder mutations were identified. If silent and suspected polymorphism mutations are excluded, frameshift, nonsense and splice mutations account for 93% in our material. mRNA in situ hybridization of BRCA1 was found to be able to identify BRCA1 and sporadic tumors with 95% specificity and sensitivity. The histology and tumor biological features of BRCA1 associated breast cancers was found to be predominantly of the ductal type, histological grade III, non-diploid with a high S-phase, predominantly TP53 positive and E