Most women have one or more risk factors for developing breast cancer but don’t get it, and some women have no so-called risk factors but end up with breast cancer. Even for breast cancer patients, it is difficult to know which risk factors are the main causes of breast cancer. Some risk factors are unavoidable, such as age, gender, etc., while others are related to the environment or personal habits, such as smoking, alcohol and diet.
Risk factors that cannot be avoided or changed
Gender: Women are the main risk factor for breast cancer, but men can also get male breast cancer, but the incidence rate is 1/100th of that of women, probably because men have very little estrogen and progesterone in their bodies, which are the main causes of breast cancer.
Age: The risk of developing cancer, including breast cancer, increases with age, with most invasive breast cancers occurring in women over the age of 55.
Genes: About 5-10% of breast cancers are genetically caused, which means that these patients inherit defective genes (gene mutations) from their parents:.
1,BRCA1 and BRCA2, the most common causes of hereditary breast cancer are mutations in the BRCA1 and BRCA2 genes. Mutations in these two genes are involved in repairing damaged DNA, and mutations lead to abnormal protein function that causes cancer. mutations in BRCA1 result in an average lifetime risk of breast cancer of 55%-65%, and for some people the risk is as high as 80%. mutations in BRCA2 result in a 45% risk of developing breast. Mutations in these two genes are also associated with ovarian cancer.
2,ATM, ATM is involved in damaged DNA, human chromosomal DNA is diploid, i.e. there are 2 copies, when both copies have ATM mutation, it causes ataxia capillaris, when 1 copy has ATM mutation, the risk of breast cancer is increased.
3,TP53, TP53 is the predominant oncogene. p53 mutations cause Li Fraumeni syndrome. People with this syndrome will have an increased risk of breast cancer and other cancers such as leukemia, brain tumors, and sarcomas.
4,CHEK2, mutations in the CHEK2 gene also cause Li Fraumeni syndrome, and even non-Li Fraumeni syndrome patients have a 2-fold increased risk of breast cancer.
5,PTEN, mutations in the PTEN gene cause Cowden syndrome, a syndrome in which people have an increased risk of breast cancer or benign breast disease, as well as an increased risk of tumors in other parts of the body such as the digestive tract, thyroid, uterus, and ovaries.
6,CDH1, mutations in the CDH1 gene cause hereditary diffuse gastric cancer, and women with this gene mutation are at increased risk of invasive lobular breast cancer.
7,STK11, the STK11 gene causes Peutz-Jeghers syndrome, which is characterized by pigmented spots on the lips and mouth and polyps in the gastrointestinal tract and urinary organs.
8,PALB2, the PALB2 gene encodes a protein that interacts with BRCA2, mutations in this gene will increase the risk of breast cancer, whether it increases the risk of ovarian cancer and male breast cancer remains unclear.
Family history: In fact 4/5 of women with breast cancer have no family history, but those with a family history will have an increased risk of developing breast cancer. The risk of breast cancer doubles if a first-degree relative (mother, sister, or daughter) has breast cancer and can triple if two first-degree relatives have breast cancer. If a first-degree relative (father, brother) has breast cancer, the risk of developing breast cancer increases as well.
Personal history of breast cancer: Patients who have had breast cancer are more likely to develop cancer in the other breast or in other parts of the same breast (non-recurrence), especially if the age of onset is young.
High density breast tissue: Women with high density breast tissue have a 1.2 to 2 times higher risk of developing breast cancer compared to women with normal breast tissue density, which can also make mammogram results inaccurate. Many factors can affect breast tissue density, such as age, menopause, certain medications (including menopausal hormone therapy), pregnancy and genetic factors.
Certain benign breast diseases: Patients with certain benign (non-cancerous) breast diseases are at greater risk of developing breast cancer. They can be classified into 3 categories based on risk.
1,Non-proliferative lesions, which have little to no increased risk of breast cancer, include.
(1) fibrosis and/or simple cysts (sometimes called fibrocystic changes or disease)
(2) Mild hyperplasia
(3) Breast adenopathy (non-sclerotic)
(4) Lobular tumor (benign)
(5) Single papillary tumor
(6) Fat necrosis
(7) Dilatation of the milk ducts
(8) Periductal fibrosis
(9) Deformation of squamous and sweat gland tissue
(10) Calcification of the dermis
(11) Other benign tumors (lipoma, malignant tumor, hemangioma, neurofibroma, adenomyoma)
2,Non-heterogeneous proliferative lesions (cellular abnormalities), which slightly increase a woman’s risk of breast cancer, include
(1) Common ductal hyperplasia (heterotypic)
(3) Sclerosing adenopathy
(4) Papilloma (papillomatous hyperplasia)
(5) Radial scarring
3,Atypical proliferative lesions, which increase a woman’s risk of breast cancer, include:
(1) Atypical ductal hyperplasia (ADH)
(2) Atypical lobular hyperplasia (ALH)
Starting menstruation before age 12: Women who start their menstrual cycle before age 12 will have more menstrual cycles than the average woman, which can lead to a slightly higher risk of developing breast cancer. The increased risk may be due to the fact that they are under the hormonal influence of estrogen and progesterone for a longer period of time during their lifetime.
Experiencing menopause after age 55: Women who go through menopause after age 55 have more menstrual cycles, which can lead to a slightly higher risk of breast cancer. The reason for this may be that they are under the influence of estrogen and progesterone hormones for a longer period of time in their lives.
Chest radiation: Young women who receive radiation to the chest for cancer (Hodgkin’s disease or non-Hodgkin’s lymphoma) have a significantly higher risk of breast cancer, depending on their age. The risk of breast cancer is also highest if chest radiation is received during adolescence, and radiation therapy after age 40 does not appear to increase the risk of breast cancer.
Exposure to hexestrol (DES): Women exposed to these drugs have a slightly higher risk of developing breast cancer. DES taken by the mother during pregnancy also leads to an increased risk of breast cancer in the child in adulthood.