¿What is breast cancer?

Cancer is caused by the loss of control of normal tissue growth. In normal tissues, the growth of new cells and the death of old cells are kept in balance; that is, the same number of cells are born and die each day. In the case of cancer, this balance is disturbed. This alteration can occur due to uncontrolled cell growth or due to the loss of the ability of normal cells to undergo “cell suicide” through a process known as “apoptosis”. Apoptosis, or “cell suicide,” is the mechanism by which old or damaged cells self-destruct.

Cancers can spread throughout the body through two mechanisms: invasion and metastasis. Invasion refers to the direct penetration of cancer cells into neighboring tissues. Metastasis refers to the ability of cancer cells to penetrate lymphatic and blood vessels, circulate through the bloodstream, and then invade normal tissues in other parts of the body. Tumors are classified as benign or malignant, depending on whether or not they can be spread by invasion or metastasis. Benign tumors are tumors that cannot spread by invasion or metastasis and therefore, only grow locally. In contrast, malignant tumors can spread by invasion and metastasis. The term “cancer”,by definition, applies only to malignant tumors.