Introduction: Histopathological features of BRCA1 and BRCA2 tumours have previously been characterised and compared with unselected breast tumours; however, familial non-BRCA1/2 tumours are less well known. The aim of this study was to characterise familial non-BRCA1/2 tumours and to evaluate routine immunohistochemical and pathological markers that could help us to further distinguish families carrying BRCA1/2 mutations from other breast cancer families.
Methods: Breast cancer tissue specimens (n = 262) from 25 BRCA1, 20 BRCA2 and 74 non-BRCA1/2 families were studied on a tumour tissue microarray. Immunohistochemical staining of oestrogen receptor (ER), progesterone receptor (PgR) and p53 as well as the histology and grade of these three groups were compared with each other and with the respective information on 862 unselected control patients from the archives of the Pathology Department of Helsinki University Central Hospital. Immunohistochemical staining of erbB2 was also performed among familial cases.
Results: BRCA1-associated cancers were diagnosed younger and were more ER-negative and PgR-negative, p53-positive and of higher grade than the other tumours. However, in multivariate analysis the independent factors compared with non-BRCA1/2 tumours were age, grade and PgR negativity. BRCA2 cases did not have such distinctive features compared with non-BRCA1/2 tumours or with unselected control tumours. Familial cases without BRCA1/2 mutations had tumours of lower grade than the other groups.
Conclusions: BRCA1 families differed from mutation-negative families by age, grade and PgR status, whereas ER status was not an independent marker.