Breast cancer

Breast cancer is the most common cancer in women worldwide. It almost never occurs in women in their teens or early twenties and it is rare in women under 35.

As in all forms of cancer, the abnormal tissue that makes up breast cancer is the patient's own cells that have multiplied uncontrollably. Those cells may also travel to locations in the body where they are not normally needed, which means the cancer is malignant. 

Breast cancer develops in the breast tissue, primarily in the milk ducts (ductal carcinoma) or glands (lobular carcinoma). The cancer is still called and treated as breast cancer even if it is first discovered after traveling to other areas of the body such as the lungs, liver, or bones. In those cases, the cancer is referred to as metastatic or advanced breast cancer.

Breast cancer usually begins with the formation of a small, confined tumor (lump) and then spreads through channels to the lymph nodes or through the blood stream to other organs. The tumor may also grow and invade tissue around the breast, such as the skin or chest wall. Different types of breast cancer grow and spread at different rates - some take years to spread beyond the breast while other move quickly. However about 80% of women with lumps are benign (not cancerous). The only safe way to distinguish between a benign lump and cancer is to have the tissue examined by a doctor.