Like other cancers, breast cancer is an uncontrolled growth of breast cells. Breast cancer occurs as a result of abnormal changes or mutation in the genes responsible for regulating the healthy growth of breast. The genes are in each cell’s nucleus, which acts as the “controller” of concern cell. 
Mutation in gene disturb/mislead the normal process of the cell, because of that cells starts abnormaly and uncontrolled  growth, producing more cells just like it and forming a tumor like structure.

This abnormal tumour-like growth can be benign (not cancerous) or malignant (cancerous property). Benign tumours are close to normal in appearance, they grow comparatively slowly, and they do not invade or spread to nearby tissue and other parts of the body. As malignant cells have the potential to grow as cancer If they left unchecked or untreated, they eventually can spread to nearby tissue and beyond an original tumour to other parts of the body.

Types of Breast cancer include:

• Angiosarcoma
• Ductal carcinoma in situ (DCIS)
• Inflammatory breast cancer
• Invasive lobular carcinoma
• Male breast cancer
• Paget's disease of the breast
• Recurrent breast cancer

Most common signs and symptoms include:

• A breast lump or thickening that feels different from the surrounding tissue
• Change in the size, shape or appearance of a breast
• Changes to the skin over the breast, such as dimpling
• A newly inverted nipple
• Peeling, scaling, crusting or flaking of the pigmented area of skin surrounding the nipple (areola) or breast skin
• Redness or pitting of the skin over your breast, like the skin of an orange