Preinvasive Cancer (DCIS)
When the malignant process is limited to the lining of the milk ducts, it is referred to as ductal carcinoma in situ (DCIS) or preinvasive cancer. At this stage, the cancer cells do not have access to the blood or lymphatic vessels and, therefore, cannot spread to the other parts of the breast or beyond.
DCIS is almost always an asymptomatic disease diagnosed by screening mammography.
The prognosis of patients diagnosed at this stage is excellent. Treatment usually consists of lumpectomy followed by radiation therapy or mastectomy without subsequent radiation. Chemotherapy is not used to treat DCIS. If untreated, substantial number of DCIS cases will progress to invasive cancer.
LCIS (lobular carcinoma in situ) is not considered a malignant process. It is a condition found incidentally when breast biopsy is performed. However presence of LCIS indicates increased risk of developing breast cancer.