The BRCA1 syndrome and other inherited breast or breast-ovarian cancers ina Norwegian prospective series

Inherited breast cancer is a heterogenous group of diseases. We examined th is heterogeneity in a prospective series of inherited breast and ovarian ca ncers. previously demonstrated to include 84% of inherited cancers. Ninety- two tumours (65 breast and 97 ovarian) in 82 patients from 70 kindreds were prospectively diagnosed. Fifteen of the breast cancers were in situ, 50 we re infiltrating. 40 (49%) of the 82 women carried a BRCA1 mutation. whereas no mutation in BRCA2 was found. Approximately, two-thirds of the BRCA1 mut ation carriers had one of the four most frequent Norwegian founder mutation s. Ninety-five per cent of the epithelial ovarian cancers occurred in BRCA1 mutation carrying women versus 38% of infiltrating breast cancers and 7% o f carcinoma in situ of the breast. The BRCA1 syndrome was phenotypically di stinct with invasive. high grade, oestrogen receptor-negative breast cancer s and epithelial ovarian cancers. Non-BRCA1/2 inherited breast cancers incl uded carcinoma in situ and lobular carcinoma and were frequently bilateral. Non-BRCA1/2 inherited breast cancer is not associated with epithelial ovar ian cancer and in breast cancers has distinct biological characteristics, i ndicating that the different subgroups of inherited breast cancer may need different healthcare services, (C) 2001 Elsevier Science Ltd. All rights re served.