Types of Breast Cancer

From the outside, the female breast appears to be a simple structure intended to fill with milk and release it for a baby when needed. Inside, however, the anatomy of the breast is quite intricate (see Inside the Breast). Several types of breast cancer can affect the structures and tissues of the breast. The aggressiveness of the cancer and the likelihood that the cancerous cells will spread to other parts of the body depend on the type of cancer involved.

Following are the most common types of breast cancer.

Ductal carcinoma in situ (DCIS).
A cancer that is contained within the milk-producing gland and is not yet able to spread beyond the immediate area is said to be in situ (see Cancer in the Breast). Ductal carcinoma in situ has not invaded the surrounding tissues of the breast, although, if neglected, it might eventually do so. For the time being, however, it doesn't have access to the blood vessels or lymphatic channels that exist in the fatty tissue outside the glands, and so it cannot migrate to other organs in the body.

DCIS is a breast cancer at its earliest stage (Stage 0), still confined to the ducts. Nearly 100% of women with cancer at this stage can be cured. In screening centers, about 20% of the new breast cancers diagnosed are DCIS, and about 80% are invasive.

On a mammogram, DCIS usually looks like a cluster of calcifications (tiny white spots or little grains of sand) without a density (larger spot). About 15% of DCIS patients also have a density, and in 10%, a density is found without calcifications. Occasionally, the doctors find the DCIS on a biopsy specimen without any sign of it appearing on the mammogram.

Invasive (infiltrating) ductal carcinoma (IDC). This is the most common form of breast cancer; roughly 80% of invasive breast cancers are IDC. This cancer has broken through the duct wall and invaded the surrounding fatty tissue of the breast. From there it can gain access to the blood vessels or lymph channels and spread to other parts of the body.

Invasive (infiltrating) lobular carcinoma. About 10% of invasive breast cancers are this type. The cancer cells have grown through the wall of the lobule and can spread to other parts of the body by way of the lymphatic channels or bloodstream.

Next >> Less Common Breast Cancers

In This Article:
Understanding Breast Cancer
What Is Cancer?
Types of Breast Cancer
Less Common Breast Cancers

From the Harvard Health Publications Special Health Report, Breast Cancer: Strategies for Living. Copyright 2004 by the President and Fellows of Harvard College. Illustrations by Harriet Greenfield, M.A., and Jesse Tarantino. All rights reserved. Used with permission of StayWell. Harvard Medical School does not endorse products.
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