There are four different types of breast cancer. They are described below.
Breast cancer is either invasive or noninvasive (often referred to as in situ). There are two types of noninvasive breast cancers: ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS). These two types of noninvasive breast cancers do not invade the basement membrane of the breast (see Fig. 1, Anatomy of the Breast). As their names suggest ductal carcinoma in situ cancer cells are found in the lining of the duct whereas lobular carcinoma in situ cancer cells are found in the lobules (see Anatomy section for a detailed description of the ductals and lobules of the breast).
There are the two types of noninvasive breast cancer described above and there are also two types of invasive breast cancer: infiltrating ductal carcinoma and infiltrating lobular carcinoma. As their names suggest, infiltrating ductal carcinoma penetrates the wall of the duct and travels to areas outside of it whereas infiltrating lobular carcinoma spreads through the wall of the lobule and also travels to areas outside of it. Infiltrating ductal carcinoma is the most common type of breast cancer, accounting for between 70%-80% of the cases of breast cancer.
Each of the four types of breast cancer has four stages that relate to the severity of the cancer. The following describes the types and stages of breast cancer.
Stage 0—noninvasive carcinomas (LCIS or DCIS). Cancer cells have not invaded the surrounding breast tissue.
Stage I—the tumor is no more than 2 cm in size and cancer cells have not spread beyond the breast.
Stage II—either the tumor has spread to the lymph nodes under the arms
but the tumor is less than 2 cm
in size, or the tumor has not spread to the lymph nodes under the arms but is greater than 5 cm in size, or the tumor is between 2 and 5 cm and may or may not have spread to the nodes.
Stage III—the tumor is greater than 5 cm in size and has spread to the lymph nodes under the arms.
Stage IV—the cancer has spread to other parts of the body (metastatic cancer).
Figure 1. Cross-Section of the Breast
MD Consult. Breast Cancer: What is Breast Cancer?
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