A cancer that starts in the cells of the breasts.

Breast cancer is cancer that starts as a growth of cells in the breast tissue. It's most common in women. Everyone is born with some breast tissue, so anyone can get breast cancer.

Symptoms include a lump in the breast or an area of thickened skin that feels different from the skin around it. Other symptoms include a nipple that turns inward and changes in the size, shape and appearance of the breast.

Breast cancer treatment often involves surgery. Other treatments include radiation therapy, chemotherapy, hormone therapy, targeted therapy and immunotherapy.