A family with hereditary breast and ovarian cancer syndrome showing a high incidence of colorectal cancer and breast cancer

Abstract

The patient has been diagnosed with quadruple cancer, including metachronous multiple colon cancer and metachronous bilateral breast cancer. She underwent surgery for right breast cancer at age 65, left breast cancer and ascending colon cancer at age 76, and transverse colon cancer at age 81. Cancer related family history included that her father passed at age60 from gastric cancer, her mother dying at age 72 from colon cancer, eldest daughter diagnosed with colon cancer at age 58, younger sister dying at age 37 from gastric cancer, niece (daughter of the deceased sister) diagnosed with breast cancer at age 37, and second younger sister diagnosed with colon cancer at age 56 and breast cancer at age 61. Lynch syndrome was initially suspected due to the strong family history of colon cancer. However, BRAF mutation (-), MSI testing (-), and immunohistochemical staining (IHC) for mismatch repair proteins in the transverse colon cancer tissue all showed no loss of expression, ruling out Lynch syndrome. Subsequently, we focused on the frequent occurrence of breast cancer and conducted BRCA genetic testing. A pathogenic mutation, c.188T>A (p.Leu63*), was detected in BRCA1, resulting in a diagnosis of hereditary breast and ovarian cancer syndrome (HBOC). IHC for BRCA1 protein was conducted on the two colon cancers and two breast cancers, confirming their association with BRCA1 mutations. This report describes a case of overlapping HBOC involving metachronous bilateral breast cancer and metachronous multiple colon cancer with a strong family history of colon cancer.