Types of Breast Cancer

Question and Answer with Ralph Maeda, M.D.
What are the types of breast cancers?
Dr. Maeda:
Breast cancer is not just one disease, but rather is a general term used to describe a number of different types of cancers that occur in the breast. The majority of breast cancers can be classified into one of the following categories; infiltrating ductal carcinoma, infiltrating lobular carcinoma, ductal carcinoma in situ, lobular carcinoma in situ, inflammatory carcinoma, Paget's disease, and cystosarcoma phyllodes. There are other tumors of the breast, such as angiosarcoma, squamous cell cancer and lymphoma, but they are quite rare. These categories are based on the microscopic appearance of the breast tissue obtained with a biopsy sample.

Infiltrating Ductal Carcinoma

Infiltrating Ductal Carcinoma begins in the cells forming the ducts of the breast. It is the most common form of breast cancer, comprising about 65-85% of all cases. On a mammogram, invasive ductal carcinoma is usually found as an irregular mass, or as a group of small white irregular dots called microcalcifications, or a combination of both. It may also appear as a lump in the breast. On physical examination, this lump usually feels much harder or firmer than other benign causes of lumps in the breast.

Infiltrating Lobular Carcinoma

Infiltrating Lobular Carcinoma comprises 5 to 10 percent of breast cancers. This type of breast cancer can appear similar to infiltrating ductal carcinoma on mammography, but on examination of the breast there is usually not a hard mass, but rather a vague thickening of the breast tissue. Lobular carcinoma can occur in more than one site in the breast (multicentric) or in both breasts simultaneously (bilateral).

Ductal Carcinoma In Situ (DCIS)

Ductal Carcinoma In Situ (DCIS) is a pre-invasive form of breast cancer. It is commonly seen in association with an invasive breast cancer. If it occurs without an invasive cancer there is usually no lump associated with it. On mammography, there may be fine microcalcifications which can signal its presence. DCIS is frequently multifocal, meaning it is located in more than one area of the breast. Approximately one-third of DCIS cases are multifocal. If DCIS is treated with biopsy alone, about 40% of women will ultimately develop an invasive cancer of that breast in the future.

Lobular Carcinoma In Situ (LCIS)

Lobular Carcinoma In Situ (LCIS) is usually encountered as an incidental finding in a breast biopsy. It has no symptoms, and has no characteristic pattern on mammography. It has been found to occur in multiple sites in the same breast in 40 to 90% of cases. In 50% of the cases, it may also occur in the opposite breast. The risk of developing an invasive cancer of the breast with LCIS is approximately 1% per year. The invasive cancer that develops has about an equal chance of being in either breast regardless as to which breast the LCIS was initially found. A large percentage (38%) of women with LCIS may not develop an invasive cancer until more than 20 years after the initial diagnosis.