Ductal carcinoma in situ (DCIS), also known as intraductal carcinoma, is the earliest form of breast cancer. It’s a non-invasive cancer in which abnormal cells are contained inside the milk duct of the breast. The condition is intraductal or “in situ,” which means “in place” or “in its original place” because the cells haven’t spread from the milk duct to invade surrounding breast tissue.
DCIS is considered a pre-cancer or pre-invasive cancer that can sometimes become an invasive cancer. About 1 in 5 new breast cancer diagnoses will be DCIS. Less than 30 percent of women with DCIS will develop an invasive breast cancer within 10 years of diagnosis, typically in the same breast and area as the DCIS was discovered.
Patients with DCIS usually don’t show any signs or symptoms although cases have been reported after a patient found a breast lump or bloody nipple discharge, according to the Mayo Clinic. Like other breast cancers, the best way to diagnose DCIS is through a mammogram. The condition shows up on a mammogram as a small group of calcifications, tiny white specks of calcium or shadows of irregular sizes and shapes inside the ducts. A genetic mutation in the DNA of the breast duct cells cause them to appear abnormal. The calcification forms within the broken-down cells as old cancer cells die off and pile up.
DCIS isn’t life-threatening, but treatment is needed to prevent the condition from becoming invasive. Referred to as having stage 0 breast cancer, the majority of patients with DCIS are cured with lumpectomy surgery and radiation. After treatment, some women may take hormone therapy.
It’s not known what causes the abnormal cell growth that leads to DCIS. Contributing factors are the same as for other forms of cancer: inherited genes, environment and lifestyle. These include: increased age, obesity, a history of benign breast disease or family history of breast cancer, having a first pregnancy after age 30 or taking hormone replacement therapy for more than 3 to 5 years after menopause.