Age – As the age increases, risk of developing malignancy increases with peak age at 75 to 80 years
Age at menarchy – Attaining menarche at age younger than 11 years increases risk by 20% when compared to women attaining menarche after 14 years
Age at 1st live birth – Women younger than 20 years at the 1st live birth have half the risk of nulliparous women or women over the age of age 35 years at their first birth. Early pregnancy leads to terminal differentiation of luminal cells thus removing them from the pool of cancer precursor cells.
First degree relatives with breast cancer – increases the risk of developing malignancy
Atypical hyperplasia – in the prior breast biopsy increases the risk of invasive carcinoma
Race/Ethnicity – Non-Hispanic white women have the highest incidence in US. This variation is probably due to frequency of breast cancer genes in particular ethnic group
Estrogen exposure – Post menopausal hormonal replacement therapy increases the risk of breast cancer by 1.2 to 1.7 folds. Adding progesterone increases the risk further.
Breast density –
Higher breast density in associated with increased risk
Higher breast density may be related to less complete involution of lobules at the end of each menstrual cycle which increases the number of potentially susceptible cells for neoplastic transformation.
Radiation exposure – Increases the risk of breast cancer. Risk is more in younger women exposed to radiation (cancer therapy or atomic bomb exposure)
Benign breast disease – Prior breast biopsies with atypical hyperplasia or proliferative changes increases the risk of developing invasive carcinomas
Diet – Moderate to heavy alcohol consumption increases risk
Obesity – Post menopausal obese women are at increased risk due to synthesis of estrogen in fat depots
Breast feeding – Longer the women breast feeds, the greater the reduction in risk . Lactation suppresses ovulation and may trigger terminal differentiation.
Carcinoma of contralateral breast and patients with endometrial carcinomas also have increased risk
References
Vinay kumar, Abul K.Abbas, Nelson Fausto, Jon C. Aster. The Breast. In: Robbins and Cotran Pathologic basis of disease. 8th edition.
