DCIS is usually identified and diagnosed through a combination of processes. Although it is rare for DCIS to present with a noticeable lump, for those women that have the symptom, their doctor may be able to feel it during a physical exam. For the women that do not have a noticeable lump, the presence of the cancer can often be detected using mammography, which is the most common way for DCIS to be identified. As old cancer cells die off, they pile up, and tiny specks of calcium form within these broken down cells. These are known as calcifications or microcalcifications. Mammograms identify the cells within the ducts as a cluster of said microcalcifications, which are visible on the mammogram as either a shadow or white specks.

If the mammogram is not suspicious, but the doctor has reason to believe something is suspicious, he or she will probably request that you have a biopsy performed. Needle biopsies can be done in one of two ways, with minimal “surgery” being required, as DCIS rarely requires more invasive biopsies. The first type biopsy available is a fine needle aspiration biopsy, which consists of a very small and hollow needle being inserted into the breast. This needle will extract a sample of cells, which can then be examined under a microscope. Fine needle aspiration biopsies leave no scars; however, some women may develop bruising at the biopsy site. The other form of biopsy is a core needle biopsy. In this procedure, a larger needle is used to extract several samples of tissue from the suspicious looking area. The larger needle allows bigger samples to be taken. The samples are then analyzed under a microscope. Because of the nature of the type of needle used in this procedure, a tiny incision must be made by the surgeon, which can leave a very tiny scar that usually becomes only slightly visible after a few weeks have passed.

On rare occasions, needle biopsies are unable to remove cells or tissue, or the results from these biopsies are inconclusive, or are not definitive. In these cases, a more surgery-like procedure is required. This can be either an incisional biopsy, which removes a solid piece of tissue that can then be examined, or an excisional biopsy, which makes an effort to remove the complete suspicious lump of tissue from the surrounding breast. Biopsies are purely a diagnostic process, and if a DCIS diagnosis is received, more surgery will be required to make sure all cancer cells are removed, including a small margin of healthy tissue that surrounds the cancerous cells, which decreases the likelihood of the cancer recurring.

Following a biopsy, a pathologist will analyze the samples of breast tissue that were taken and will report back on both the grade and type of DCIS and the hormone receptor status. The typing grade of DCIS is determined by the abnormal appearance of cells when they are compared with normal breast cells, as well as the speed of their growth rate. The hormone receptor status indicates whether the cells are responsive to estrogen and/or progesterone. Responsiveness means that the cells within the cancer contain proteins that react to these hormones, which fuels cancer cells’ growth. Cancers that are hormone receptor positive usually require some form of treatment that minimizes or altogether blocks or removes the presence of these hormones.