Breast Cancer (Facts, Stages) (cont.)

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Definitive diagnosis

Even if imaging tests show an abnormality or are suspicious for breast cancer, definitive diagnosis requires a tissue sample, or biopsy. A biopsy may be taken of a small area of the abnormality (an incisional biopsy), or the entire abnormal area may be removed at the time of biopsy (excisional biopsy). Biopsy allows the pathologist (a physician with special training in the diagnosis of diseases based on the morphology of tissue samples) to determine if cancer is present and, if so, what type of cancer. Biopsy also provides a tissue sample for further tests that are done (see below) to determine the best type of treatment.

Specialized breast cancer testing

Certain tests are routinely performed on breast cancer tumor samples to help determine the optimum type of treatment. These include the following:

  • Hormone receptor status: Breast cancer tissue is tested to look for the presence of receptors for the hormones estrogen and progesterone. Tumors are termed estrogen receptor-positive (ER+) or progesterone receptor-positive (PR+) if these receptors are present. This means that tumor growth is responsive to hormonal changes and that hormone-directed therapies may be effective in stopping growth.
  • HER2: Another standard test measures the overexpression of a protein called HER2 on the breast cancer cells. If a tumor is HER2-positive (HER-2+), targeted therapies against this protein may be given.

About 15% of women have breast cancers that do not express any of these tumor markers (ER, PR, or HER2). These tumors are called triple-negative breast cancers.

Newer laboratory tests may be useful for some types of tumors to help determine the prognosis and treatment plan. These include, for example, studies of gene expression in the particular tumor or tests to look for circulating tumor cells.

Medically Reviewed by a Doctor on 9/29/2014

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