What causes breast cancer?
I. Several major factors known to induce breast cancer.
1. Age: In women, the incidence rate rises with age, rare before the first menstruation and rare before the age of 20, but the incidence rate rises rapidly after the age of 20, higher at the age of 45-50, but in a relative flat, and the incidence rate continues to rise after menopause, reaching a peak around the age of 70. The mortality rate also rises with age, with a gradual increase in mortality after the age of 25, and always maintains an upward trend until old age.
2.Hereditary factors: Women in the family who have a history of breast cancer in first degree direct relatives’ family have 2-3 times more risk of breast cancer than the normal population.
3.Other breast diseases.
Age of menarche: The risk of menarche is 2.2 times higher than that of women older than 17 years old.
5.Age of menopause: The risk of menopause is increased for those who are older than 55 years old than those who are younger than 45 years old.
6. Age of first pregnancy: the risk increases gradually with the postponement of the age of first birth, and the risk is higher for those who have their first birth after 35 years old than for those who have no history of childbirth.
7. Post-menopausal estrogen supplementation: Long-term use of estrogen during menopause may increase the risk of breast cancer.
8.Oral contraceptive pills.
9.Food: Especially fatty diet can increase the risk of breast cancer.
10.Drinking alcohol.
11. Weight gain may be an important risk factor for breast cancer in postmenopausal women.
12.Viral infection.
13.Radiological effects: It is easy to increase the risk of breast cancer.
14.Mental factors: anxiety and tension can suppress the immunity against cancer.
Pathogenesis
1. Genetic factors: Some patients in female breast are caused by the transmission of genes, i.e. the younger the age of onset, the greater the genetic tendency. With the in-depth study of the pathogenesis of hereditary breast cancer, it may be elaborated in the future.
The characteristics of hereditary breast cancer are.
(1) Young age of onset.
(2) Susceptibility to bilateral onset.
(3) The relatives of patients with premenopausal breast cancer are also prone to develop the disease before menopause.
Gene mutation: Oncogenes can have two synergistic stages, i.e., initiation stage and promotion stage. The relationship between oncogenes and their products with the occurrence and development of breast cancer has been concluded as follows: there are several kinds of oncogenes involved in the formation of breast cancer; the first introduction of oncogenes in normal cells does not necessarily lead to tumor, but may involve several times before cancer occurs; oncogenes are not only involved in the initiation stage, but also play a role after the formation of breast cancer; during the process of normal breast epithelial cells – proliferation – cancer, oncogenes are involved in the development of breast cancer. In the process of normal breast epithelium – proliferation – cancer, there may be different genes involved.
(1) Radiation exposure can cause gene damage and chromosome mutation, leading to breast cancer development.
(2) Endocrine hormones stimulate the proliferation of breast epithelial cells, and animal experiments show that estrogen mainly acts in the promotion stage of cancer formation, while normal female endocrine hormones are in a dynamic balance, so the occurrence of breast cancer is directly related to endocrine disorders.
Estrogen, progesterone, prolactin, androgen and thyroid hormones are all related to the development of breast cancer. The level of estrogen in the breast is several times higher than the level of estrogen in the blood. Cholesterol and its oxidation products, i.e. cholesterol epoxide, in the mammary gland can induce mammary epithelial cell proliferation, and cholesterol epoxide itself is a mutagenic, carcinogenic and cytotoxic compound.
(3) Exogenous hormones, such as oral contraceptives, therapeutic estrogens and androgens, can cause imbalance of the above endocrine hormone balance in the body and produce corresponding effects.
(4) The relationship between dietary components and certain metabolites such as fat and breast cancer: the incidence of mammary tumors in mice with hyperlipidemia caused by animal and vegetable oils is increased. In the initiation stage of carcinogenic effect of carcinogenic agents on mice, increasing the amount of fat does not work, but in the promotion stage, fat feeding increases and tumor growth is rapidly accelerated.
3.Decreased immune function of the body: Decreased immunity of the body and its inability to remove carcinogenic substances and mutated cells induced by carcinogens in time is one of the important factors in the host aspect of breast cancer. As age increases, the immune function of the body, especially the cellular immune function, decreases, which is one of the reasons why most tumors, including breast cancer, tend to occur in middle and old age.
4. Neurological function status: Many breast cancer patients had mental trauma before the onset of the disease, indicating that the higher nervous system is overstressed, which may provide favorable conditions for carcinogenic agents to induce mutations.