DCIS is a high risk non-invasive lesion that is “in place” and cannot spread. Approximately 20% of DCIS will transform into breast cancer if left untreated. The challenge for your oncologist is that it is difficult to know which cases of DCIS will transform into a cancerous tumour and thus everyone is treated for this lesion in a similar manner to prevent a cancer from establishing itself.

DCIS generally has no signs or symptoms. A small number of people may have a lump in the breast or some discharge coming out of the nipple. According to the National Cancer Institute, about 80% of DCIS cases are found by screening mammography.

Another in situ form of localized non-invasive disease is called LCIS. There are two main forms of LCIS, classical and pleomorphic. Classical is much more common than pleomorphic. These are non-invasive lesions that remain within the breast lobule and do not grow beyond it. It is not a cancer. “In situ” means that a lesion does not pass the basement membrane which is why this lesion cannot spread to the lymph nodes or other organs. LCIS is thus, non life-threatening. The classical type is merely an indicator of risk and extensive surgery is not required. Pleomorphic LCIS, however, acts more like DCIS as a high risk lesion, that in some cases may develop into an invasive cancer by continuing to grow beyond the basement membrane and this is why the recommendation is to remove it, to prevent this from happening.

Standard treatment options for DCIS (and LCIS) include:

• Lumpectomy followed by radiation therapy: This is the most common treatment for DCIS. Lumpectomy is sometimes called breast-conserving treatment or surgery (BCT and BCS) because most of the breast is preserved.
• Mastectomy: Mastectomy, or removal of the breast, is recommended in some cases of very extensive DCIS that is throughout the majority of the breast. In this case radiation is not required.

Chemotherapy, a form of treatment that sends anti-cancer medications throughout the body, is generally not needed for DCIS. DCIS is non-invasive and remains within the breast duct, therefore additional treatment to attack cancer cells that might have traveled to other areas of the body is usually unnecessary. One exception to this is DCIS that is ER/PR + may benefit from post-operative hormone therapy to reduce the likelihood of recurrence.