Milk ducts. Ductal carcinoma is the most common type of breast cancer. This type of cancer forms in the lining of a milk duct within your breast. The ducts carry breast milk . In situ breast cancer (ductal carcinoma in situ or DCIS) is a cancer that starts in a milk duct and has not grown into the rest of the breast tissue. The term invasive (or infiltrating) breast cancer is used to describe any type of breast cancer that has spread (invaded) into the surrounding breast tissue. Ductal carcinoma in situ (DCIS).
Sep 29, · Even though the majority of breast lumps are caused by less severe conditions, new, painless lumps are still the most common symptom of breast cancer. Early Author: Brian Krans.