Breast cancer is a malignant tumor that starts from the cells of the breast. A malignant tumor is a group of cancer cells that may invade surrounding tissues or spread (metastasize) to distant areas of the body.

The disease occurs almost entirely in women, but men can get it too. Breast cancer, the second leading cause of cancer deaths in American women, is the disease women fear most.

Symptoms
Knowing the signs and symptoms of breast cancer may help save your life. When the disease is discovered early, you have more treatment options and a better chance for a cure. Most breast lumps arent cancerous.

Yet the most common sign of breast cancer for both men and women is a lump or thickening in the breast. Often, the lump is painless.

Other potential signs of breast cancer include:

• A spontaneous clear or bloody discharge from the nipple, often associated with a breast lump.

• Retraction or indentation of the nipple

• A change in the size or contours of the breast.

• Any flattening or indentation of the skin over the breast

• Redness or pitting of the skin over the breast, like the skin of an orange.

Causes:
In most cases, it isn't clear what causes normal breast cells to become cancerous. Doctors do know that only 5 per cent to 10 per cent of breast cancers are inherited. Yet most genetic mutations related to breast cancer aren't inherited.

These acquired mutations may result from radiation exposure-women treated with chest radiation therapy for lymphoma in childhood or during adolescence when breasts are developing, have a significantly higher incidence of breast cancer than do women not exposed to radiation.

The most common type of breast cancer begins in the milk-producing ducts, but cancer may also begin in the lobules or in other breast tissue.

Researchers are now trying to discover whether a relationship exists between a person's genetic make up and environmental factors that may increase the risk of breast cancer. Breast cancer eventually may prove to have a number of causes.