Lobular Carcinoma in situ (LCIS): When the normal lining cells of the lobules begin to grow out of control, the cells will heap up, and under the microscope are seen one or more lobules filled with these abnormal cells:
Lobular carcinoma in situ is the least serious breast tissue abnormality, but its presence does place the patient at a higher than normal risk of later developing true breast cancer. The LCIS growth shoyold be removed surgically, and the patient should be followed carefully with mammography and physical breast exams for the rest of her life.
Ductal Carcinoma in situ (DCIS): This in situ tumor develops when the lining cells of the breast ducts begin to grow out of control with cells that are pre-malignant. These in situ cancer cells, however, stay inside the basement membrane sleeve of the duct; the tumor does not invade through the basement membrane. Another name for DCIS is intraductal carcinoma of the breast because the carcinoma stays "within" the ducts.
The individual cancer cells that are growing in DCIS are believed to be true cancer cells. If untreated, or if treated inappropriately, these cancer cells may eventually develop ability to invade through the basement membrane and become an invasive (or infiltrating) carcinoma with the ultimate ability to spread through the body.