Ductal carcinoma in situ (DCIS) is the most common form of non-invasive breast cancer, and refers to abnormal cells that are confined to the milk ducts of the breast. “In situ” refers to the cancer being restricted to its original site; that is, it has not invaded the tissue surrounding the milk duct.
DCIS generally does not present as a palpable lump in the breast, and is most often found instead on mammography. DCIS is associated with areas of “calcification” or “microcalcification”, as calcium accumulates in broken-down cancer cells.
If your mammogram shows areas of suspicion, such as microcalcifications, a core biopsy will be performed, in order to provide a clear diagnosis. These biopsies are minimally invasive, although occasionally a surgical biopsy may be required if earlier results are unclear.
DCIS must be removed surgically, typically through a “lumpectomy” also known as a wide local excision. Radiotherapy to the breast is usually required post operatively. A mastectomy with or without immediate breast reconstruction may be performed if there are large areas of DCIS, as clear margins of healthy tissue must be excised to ensure that the entire tumour is removed. Patients undergoing a mastectomy for DCIS will not require post operative radiotherapy.
Having DCIS increases the risk of an invasive cancer developing. There is always a small risk of recurrence (of either DCIS or invasive cancer) after a lumpectomy. The likelihood of recurrence is reduced when radiation therapy is given following surgery. Typically recurrence occurs within five to ten years following the initial diagnosis although it may occur many years after the initial diagnosis. The risk of recurrence is reduced if a good margin of normal tissue is taken around the DCIS.