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Types of Breast Cancers

Cancerous cells most commonly appear in the portions of the breast that produce and transport milk, specifically the lobules and the ducts. When cancerous cells are contained in these structures they are said to be 'in situ' (from Latin meaning "in its own situation"). 'In situ' cancers are the very earliest and most treatable forms of cancer.

Lobular carcinoma in situ (LCIS)
LCIS is considered a marker of increased risk of breast cancer rather than an actual cancer. It is often found incidentally in breast biopsies. Both breasts are subsequently at increased risk of developing breast cancer. Regular surveillance including twice yearly clinical breast examinations and mammography are essential. Women with LCIS may consider the use of tamoxifen for prevention and occasionally some women may opt for a bilateral prophylactic mastectomy (the preventative removal of both breasts).

Ductal carcinoma in situ (DCIS)
This is the earliest stage (stage 0) of breast cancer, when the cancer is confined to the ducts. DCIS makes up about 20 percent of all detected breast abnormalities by the Ontario Breast Screening program and 16 percent at subsequent screenings. Caught at this stage, treatment success is high, nearly 100 percent. If the cells are left to change and spread, the lesion could infiltrate surrounding tissues as a form of invasive breast cancer.

Infiltrating (invasive) lobular carcinoma (ILC)
This cancer starts in the lobules or milk glands and can spread to other parts of the body. ILC makes up about 10 to 15 percent of all breast cancers. ILC is often difficult to feel or see on a mammogram.

Infiltrating (invasive) ductal carcinoma (IDC)
This cancer starts in a duct and invades the fatty tissue of the breast. IDC accounts for nearly 80 percent of all breast cancer.

Inflammatory breast cancer
Inflammatory breast cancer is an uncommon type of breast cancer that can grow and spread quickly even in early stages. It can develop when breast cancer cells block the lymph vessels that remove fluids, bacteria and other waste products from breast tissue. As a result, the breasts can become inflamed. Unlike the most common types of breast cancers, inflammatory breast cancer tends to grow in layers or nests. Symptoms cancer can appear suddenly, and include a change in the size or shape of your breast, breasts that are hot or itchy to the touch, a change in the normal colour of your breasts, or a change in texture. Skin may have a pitted appearance similar to the skin of an orange.


Many breast lumps and changes are not actually cancer, but are benign conditions, tumours or cysts. However, it is important to have any new lumps checked by a doctor as soon as possible.


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  • A publication of:
  • Women's College Hospital