In the midst of a cancer diagnosis for yourself or someone you love, it can be difficult to keep the medical terminology straight. 
These definitions may help: 
In situ. A Latin term that means in place. This means that the cancer is confined to the area where it began. 
Invasive or infiltrating breast cancer. This is cancer that has broken through the lobules (sections that produce milk) or ducts (tubes that carry milk to the nipple) into the surrounding tissue. 
Ductal carcinoma. This cancer begins in the cells that line the milk ducts.&nbsp;
Ductal carcinoma in situ (DCIS).&nbsp;This condition is also called noninvasive carcinoma and intraductal carcinoma. These abnormal cells in the breast ducts haven't spread to other breast tissue. It's possible that this cancer could become invasive in the future.&nbsp;&nbsp;
Invasive ductal carcinoma. The abnormal cells in the ducts have spread to other parts of the breast tissue. These cells can also spread to other parts of the body.&nbsp;It is the most common type of breast cancer.
Lobular carcinoma. This type of breast cancer starts in the lobules of the breast. 
Lobular carcinoma in situ (LCIS). This is a condition in the lobules that usually does not develop into cancer, but it does increase your risk for developing breast cancer later on. It can occur in both breasts independently. Because it doesn't form a lump and isn't usually visible by mammography, LCIS tends to be detected only when a breast biopsy is done to investigate some other abnormality. 
Invasive lobular carcinoma. The cancer cells have spread from the lobules to nearby breast tissue. They can also spread to other parts of the body. 
Metastatic breast cancer. The breast cancer appears in another organ. It is still considered breast cancer because it started in the breast. 
Inflammatory breast cancer. This rare form of breast cancer makes the breast skin feel warm or appear red, ridged or pitted. It tends to spread quickly to other parts of the body. 
Reviewed 10/11/2023

Breast cancer terms

Definitions of some commonly used medical terminology.