Most breast cancers begin in the breast's ducts or glands (lobules). Some begin in the cells that line the lobules (lobular cancers), while a small number start in other tissues, according to the American Cancer Society. Where it starts is determined by how the cells appear under a microscope.
Here are the most common types, according to mayoclinic.com:
INVASIVE: This type of breast cancer has spread into the tissues surrounding the membrane of the duct or lobule. From there it can spread to other parts of the body. Most common among invasive breast cancers are invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC).
About 70 percent of all breast cancers are the IDC type, the Mayo Clinic reports. The cancer cells form in the lining of the milk duct, then break through and invade surrounding tissue. They may remain in that area or spread into other regions via blood circulation or lymph nodes.
ILC is less common than IDC, but invades in a similar way. It starts in the lobules, breaks through into the surrounding tissue and can spread to other parts of the body. With ILC, you may feel more of a thickness than a lump in the breast.
IN SITU: Here the cancer cells have remained within their place of origin. Most common among these non-invasive cancers is ductal carcinoma in situ (DCIS) which is contained in the milk duct lining. With treatment, this has an excellent prognosis.
Breast cancer occurs primarily in women, but men can get it too. Men make up fewer than 1 percent of the cases because their breast duct cells are less developed than women's and their breast cells aren't hit with the same growth-inducing effects. Most cases are discovered in men ages 60-70, says the National Cancer Institute.Copyright © 2014, Los Angeles Times