Breast cancer is a cancer that starts in the tissues of the breast. There are 2 main types of breast cancer:

• Ductal carcinoma: This starts in the tubes (ducts) that carry milk from the breast to the nipple. Most breast cancers are of this type.
• Lobular carcinoma: This starts in the parts of the breast, called lobules, which produce milk.

Treatment

Treatment is based on the

• Type of breast cancer
• Stage of the cancer 
• Whether the cancer is sensitive to certain hormones
• Whether the cancer overproduces (overexpresses) the HER2/neu protein

Cancer treatments include:

• Hormone therapy.
• Chemotherapy, which uses medicines to kill cancer cells.
• Radiation therapy, which is used to destroy cancerous tissue.
• Surgery to remove cancerous tissue:
• Targeted therapy uses medicine to attack the gene changes in cancer cells. Hormone therapy is an example of targeted therapy. It blocks certain hormones that fuel cancer growth.

Prognosis

New, improved treatments are helping people with breast cancer live longer. Factors that determine the risk for recurrence and the likelihood of successful treatment include:

• Location of the tumour and its spread.
• Whether the tumour is hormone receptor-positive or -negative
• Tumour markers
• Gene expression
• Tumour size and shape
• Rate of cell division or how quickly the tumour is growing

Know more About breast cancer