Abstract

PIP: This review of breast carcinoma etiological factors considers the following: heritage; menses, marital state, and parity; breastfeeding; contraceptives; benign epithelial diseases of the breast; hormonal factors; cancer; iatrogenic factors; immunological factors; viral aspects of human breast cancer; dietary factors; and psychosomatic factors. Breast carcinoma is the most prevalent type of cancer in American women. 8% of American women can expect to be stricken with this disease. The rate in men is 1% that in women. The causes or reasons for a woman being afflicted with this disease remain equivocal. An abundance of evidence exists that the incidence of breast carcinoma varies greatly from 1 population to another throughout the world and that in most populations it is increasing. Due to earlier detection, improved medical care, and possible other factors, the death rate is not increasing as rapidly as the incidence rate. In general, the incidence is greatest in populations with the highest standards of living, such as those of Northwestern Europe and North America. Thus, a woman's heritage is usually a large factor in determining her low risk of developing mammary carcinoma. Heritage includes family, race, country of origin, religion, and any component of lifestyle that is firmly passed on from 1 generation to the next. These factors seem to have a great influence on the incidence of breast cancer, but there is little agreement on which components of heritage are most important and how they operate. Many publications report insignificant or no effect of menarchal age on breast cancer risk. Many reports mention breastfeeding along with other data in breast cancer etiological studies, but its influence on the disease seems to be insignificant. Possibly there is some synergistic influence, but available data is not strong enough to establish the direction. Many reports seem to suggest that oral contraceptives (OCs) increase risk in nulliparous women and may promote the growth of malignant neoplasia, but in parious women, if there is no incipient cancer present, OCs do not appear to increase risk and may even decrease risk. Benign epithelial lesions can be harbingers of breast carcinoma, but from the literature it is not easy to conclude the nature of the most risky lesions nor their relative risks. A familial or personal history of cancer in any location or tissue may increase the risk of breast cancer. Ionizing radiation, oophorectomy, hysterectomy, and hormone therapy are the principal iatrogenic factors that influence the incidence of breast cancer. Radiation is known to be a most powerful carcinogen and is probably responsible for more cancer than any other iatrogenic factor. None of the factors so far studied is of great importance singly, but in a situation where several act together, any one may appear to be significant.