Breast Cancer

Specific criteria must be met to diagnose any kind of cancer. To understand how breast cancer is diagnosed, we will briefly review the structure and function of the normal breast. Any mammal can develop breast cancer. In humans, breast cancer can be found in women and men but is far more common in women.

Structure of the Healthy Breast

The breast is made up of a few specific types of tissue. The majority of the tissue in the breast is classified as stroma, which is both fatty tissue and connective tissue and gives the breast its size and shape.

The stroma surrounds the other types of tissue that are found within the breast. These include lobules, which produce the milk in the breast. Milk production is occurs as a result of hormonal changes during pregnancy just prior to birth and while continuing to nurse. Lobules empty the milk into ducts, which carries the milk within them and ultimately is released from the nipple. There are also blood vessels, nerves and lymphatic channels throughout the breast. Breast cancer can begin in ducts, lobules or within the stroma of the breast. The most common types of breast cancer are ductal followed by lobular.

Women over the age of 55 are more likely to develop cancer than younger women, but when cancer is found in women under the age of 45 it tends to be much more aggressive, have a genetic component and leaves more time for the possibility of recurrence at some point in the woman’s life. 1

What Causes Breast Cancer

Less than 10% of all breast cancer cases are due to genetics and are caused by inherited gene mutations. The other 90% of cancers are develop spontaneously, and are the result of multiple risk factors, including environmental exposures.

The most common genetic mutations associated with breast cancer are BRCA1 and BRCA2 mutation, but other genes play a role as well. 2 When non-mutated, these genes produce cancer-preventing proteins that stop the division of abnormal cells. If they are mutated, they cannot perform this function, allowing cancer cells to continue dividing.

Studying the Pathways

Ongoing studies are taking place, trying to understand the specific pathways or sequence of events that lead to the development of breast cancer. There are many genes that have been shown to participate in the development of breast cancer. These include CHEK2, ATM, BRIP1, PALB2, NAT1 and NAT2 and several others. 3 Recent technological advances have led to a greater understanding of the correlation between genetic mutations and the development of breast cancer.

Breast cancer research continues to find improved treatment options and have become quite specific to an individual’s cancer.


1 Anders, C. K., Hsu, D. S., Broadwater, G., et al. (2008). Young Age at Diagnosis Correlates With Worse Prognosis and Defines a Subset of Breast Cancers With Shared Patterns of Gene Expression. Journal of Clinical Oncology , 3324-3330.

2 Lacroix, M., Toillon, R.-A., & Leclercq, G. (2006). p53 and breast cancer, an update. Endocrine Related Cancer , 293-325.

3 Dunning, A. M., Healey, C. S., Pharoah, P. D., et al. (1999). A Systematic Review Of Genetic Polymorphisms and Breast Cancer Risk. Cancer Epidemiology, Biomarkers & Prevention, 843-854\

This article was originally published on July 27,2012 and last revision and update of it was 9/2/2015.