Tumors of the breast originate from normal cells within breast tissue that transform into cancerous cells. Once these changes occur, cancerous cells undergo rapid, uncontrollable growth and form a solid tumor, which can invade the breast and other tissues. It is important to understand the different types and stages of these breast tumors to direct treatment.
In Situ Breast Tumors
In situ or non-invasive breast tumors are not tumors per se, but rather slight changes of cells within the breast that may indicate the presence of potentially tumorigenic cells. Advances in mammography have allowed for the detection of subtle changes in breast tissue that indicate the onset of breast cancer. According to the American Cancer Society, these changes occur in the cells lining the milk duct of the breast or lobes of the milk duct and are referred to as ductal carcinoma in situ or lobular carcinoma in situ, respectively. In situ tumors are typically too small to be noticed by manual exam or by any symptoms in the breast. Left untreated, there is a high likelihood that these in situ tumors will develop into more aggressive and dangerous tumor types.
Invasive Breast Tumors
As an in situ tumor grows, it further invades the tissue of the breast. According to the National Cancer Institute, the majority of breast tumors are invasive ductal tumors, making up about 80% of breast cancer cases. Lobular tumors can also develop into invasive carcinomas, which make up about 10% of breast cancers.
Metastatic Breast Tumors
As invasive tumors grow and develop, cells from the tumors can find their way to the blood and lymphatic systems and access distant parts of the body through the process of metastasis. According to the Mayo Clinic, metastatic tumors are very dangerous as they can damage vital organs such as the lungs, liver and brain.
Paget's Disease of the Nipple
This rare form of breast cancer (1% of breast cancer cases) originates from cells surrounding the nipple. The American Cancer Society explains that as this cancer develops, it invades the areola and the skin of the nipple. This cancer is almost always found in conjunction with some form of ductal carcinoma.
Phyllodes Tumor
The Mayo Clinic describes this rare type of breast cancer as originating from the connective tissue of the breast, rather than the milk ducts or lobes. Most of the time these tumors are benign, but they can be malignant and are removed by surgery. These tumors make up about 1% of the incidence of breast cancer.
