In many cases it is not possible to tell from a mammogram alone whether a growth is benign or cancerous. To make this determination it is necessary to obtain a tissue sample for microscopic examination. As an alternative to open surgical biopsy, which removes a larger specimen for microscopic analysis, a hollow needle may be passed through the skin into the suspicious lesion with the help of special breast x-rays. The sample of breast tissue obtained in this way can show whether the lesion is malignant or benign and the procedure is much less invasive than the surgical approach. A special computerized mammography machine uses intersecting coordinates to pinpoint the area of tissue change. This method is called stereotactic biopsy or x-ray-guided biopsy. A pathologist examines the removed specimen and makes a final diagnosis.
This procedure may be performed when:
- A woman has a mammogram showing a suspicious solid mass that cannot be felt on breast examination.
- A woman has a mammogram showing a suspicious cluster of small calcium deposits.
- The structure of the breast tissue is distorted.
- A new mass or area of calcium deposits is present at a previous surgery site.
- The patient or physician strongly prefers a non-surgical method of assessment.
A specially designed table is used for stereotactic breast biopsy. The patient lies face-down with her breast projecting through a hole in the table. The biopsy is done below the table after raising it to gain access to her breast.
The skin is cleansed and a local anesthetic is injected. A small nick is made in the skin and the tip of the biopsy needle is advanced to the previously calculated site of the lesion. At this point stereo images are obtained to confirm that the needle tip is actually within the lesion. Usually six to 12 samples are collected. Then a final set of images is obtained. If they show that the lesion has been mostly or completely removed, a small clip is left at the biopsy site so that it can be easily located if the lesion proves to be cancer. Once the biopsy is complete the skin opening is covered with a dressing; it need not be sutured.
