Breast cancer
Breast cancer is cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 originating from breast
The breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.Both men and women develop breasts from the same embryological tissues...

 tissue, most commonly from the inner lining of milk
Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...

Duct (anatomy)
In anatomy and physiology, a duct is a circumscribed channel leading from an exocrine gland or organ.-Types of ducts:Examples include:-Duct system:...

 or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinoma
Lobular carcinoma
Lobular carcinoma is a form of tumor which primarily affects the lobules of a gland.It is sometimes considered equivalent to "terminal duct carcinoma".If not otherwise specified, it generally refers to breast cancer. Examples include:...

s. Breast cancer is a disease of human
Humans are the only living species in the Homo genus...

s and other mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s; while the overwhelming majority of cases in humans are women, men can also develop breast cancer.
The size, stage, rate of growth, and other characteristics of the tumor determine the kinds of treatment.