Background: Approximately 30 % of all breast cancer is at least partly attributed to hereditary factors. Familial\nbreast cancer is often inherited in the context of cancer syndromes. The most commonly mutated genes are BRCA1\nand BRCA2 in hereditary breast and ovarian cancer syndrome. The genetic background in families with hereditary\nbreast cancer without predisposing germ line mutations in BRCA1 and BRCA2 (non-BRCA families) is still to a large\nextent unclear even though progress has been made. The aim of this study was to compare cancer proportions in\nfamilial non-BRCA hereditary breast cancer compared to the general population in search of putative new breast\ncancer syndromes.\nMethods: Pedigrees from 334 non-BRCA hereditary breast cancer families in the county of Stockholm, Sweden,\nwere investigated and the distribution of cancer diagnoses other than breast cancer was compared with the\ndistribution of cancer diagnoses in the general Swedish population in two reference years, 1970 and 2010.\nA cancer diagnosis was regarded as overrepresented in the non-BRCA families if the confidence interval was\nabove both population reference values.\nResults: We found that endometrial cancer was overrepresented in the non-BRCA families with a 6.36 % proportion\n(CI 4.67ââ?¬â??8.2) compared to the proportion in the general population in the reference years 1970 (3.07 %) and 2010\n(2.64 %). Moreover tumours of the ovary, liver, pancreas and prostate were overrepresented.\nConclusion: In conclusion, we found an overrepresentation of endometrial cancer in our cohort of hereditary\nnon-BRCA families. Our result supports previous inconsistent reports of a putative breast and endometrial cancer\nsyndrome. An association has been suggested in studies of families with several cases of breast cancer in close\nrelatives or bilateral breast cancer. To clarify this issue we suggest further studies on a breast and endometrial\ncancer syndrome in cohorts with a strong pattern of hereditary breast cancer. Identifying new breast cancer\nsyndromes is of importance to improve genetic counselling for women at risk and a first step towards detection\nof new susceptibility genes.
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