Abstract
Among Swedish families with an inherited predisposition for breast cancer, less than one third segregate mutations in genes known to be associated with an increased risk of breast cancer in combination with other types of tumours. In a search for new putative familial breast cancer syndromes we studied Swedish families undergoing genetic counselling during 1992-2000.Four thousand families from counselling clinics in Sweden were eligible for study. Families with breast cancer only were excluded, as were families with mutations in genes already known to be associated with malignant diseases. We identified 803 families with two or more cases of breast cancer and at least one other type of cancer. The observed proportion of different types of non-breast cancer was compared with the percentage distribution of non-breast cancer tumours in Sweden in 1958 and 1999.We found tumours in the colon, ovary, endometrium, pancreas and liver, as well as leukaemia in a significantly larger proportion of the study population than in the general population in both years. These tumours were also seen among families where several members had one additional tumour, suggesting that malignancies at these sites, in combination with breast tumours, could constitute genetic syndromes. Endometrial carcinoma has not previously been described in the context of breast cancer syndromes and the excess of malignancies at this site could not be explained by secondary tumours. Thus, we suggest that endometrial carcinoma and breast cancer constitute a new breast cancer syndrome. Further investigation is warranted to categorize phenotypes of both breast and endometrial tumours in this subgroup.
Highlights
Breast cancer is by far the most frequently diagnosed malignant tumour in females: one Swedish woman in ten will be affected during her lifetime [1]
We explored the occurrence of families with one or several types of additional malignancies including multiple cases of each type and together with two or more breast cancer cases
In the study families tumours in the colon, ovary, endometrium, pancreas and liver, as well as leukaemia, were statistically over-represented compared to the calculated proportion from the official statistics of the years 1958 and 1999 (Table 1)
Summary
Breast cancer is by far the most frequently diagnosed malignant tumour in females: one Swedish woman in ten will be affected during her lifetime [1]. A Scandinavian twin study has revealed that hereditary factors are important in 27% of all breast cancers [2], and 5-10% of the cases appear. Familial aggregations of breast cancer have been observed all over the world; in general, early onset and bilateral disease are two important features in these families [4]. Studies have revealed that autosomal dominant inherited mutations in certain genes are associated with an increased risk of breast cancer. Breast cancer in association with other tumours constitutes different syndromes in these families. A substantial risk of breast cancer as well as ovarian cancer is seen in women harbouring a mutation in BRCA1 or BRCA2 [5]
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