Ductal Carcinoma in Situ is diagnosed by examination of the biopsy of breast tumor. The cancer cells are within the milk ducts and have not invaded the underlying tissue. It is classified as Stage 0 breast cancer. The incidence of DCIS has increased with the widespread use of screening mammography and it now accounts for 20-30% of all newly diagnosed breast cancers.
The treatment of DCIS has become controversial. Even the name is a source of controversy. Some believe it should not be called cancer at all, since it doesn’t involve tissue invasion.