Volume 4, Issue 3, December 2009
KHOO, Ui Soon
Clinical Associate Professor, Department of Pathology, The University of Hong Kong, Queen Mary Hospital
Background
Breast cancer is the leading female cancer in Hong Kong. Now at 52.1 per 100,000 (Hong Kong Cancer Registry, 2008) its incidence has been steadily rising over the last few decades, and is the highest reported in Asian regions. There are two major breast and ovarian susceptibility genes, BRCA1 and BRCA2. About 30-70% of patients with hereditary breast/ovarian cancer and about 5-10% of all breast and/or ovarian cancer cases harbor a germline mutation in these genes 1. The defective gene is inherited in autosomal dominance pattern. Individuals carrying a mutation in the BRCA1 or BRCA2 genes have a 85% lifetime risk of breast cancer, and a lifetime risk for ovarian, fallopian tube or primary peritoneal cancer that ranges from 35-60% for BRCA1 and 10-27% for BRCA2 2.
BRCA mutation carriers tend to develop breast cancer at a young age, may have bilateral breast cancer or have a personal history of both breast and ovarian cancer. There is also an increased risk for prostate and pancreatic cancer as well as male breast cancer in BRCA2 mutation carriers. Other features of increased likelihood of hereditary susceptibility include the presence of two or more individuals in the family with breast cancer, the presence of both breast and ovarian cancer in the family, breast cancer in one or more male family members, and one of more members with two primary cancers. To estimate the probability of heritable genetic mutation in a family, one has to take into account the age of onset of breast cancer, the number of affected relatives, biological relationships of affected relatives, the ratio of affected to unaffected relatives as well as the presence/absence of associated malignancies and ethnic background.