When a suspicious finding is detected either during a manual examination (self-examination or routine examination by a physician) or through imaging tests (mammography/ultrasound or magnetic resonance imaging), cell or tissue sampling is necessary. The sampling is usually done percutaneously (through the skin) using special needles. Nowadays, it is uncommon for the first step to be surgical tissue sampling, which allows for optimal treatment planning and avoids unnecessary surgeries.
When the suspicious finding is a palpable lump during a manual examination, the sampling can be performed through palpation in the clinic. If the suspicious finding is not palpable, the sampling can be done under the guidance of imaging. In such cases, if the finding can be identified by ultrasound, the sampling will be ultrasound-guided, as it is simpler than sampling under mammography guidance.
If the suspicious finding is detected in mammography and not confirmed by ultrasound, the sampling will be performed under mammography guidance using the method called stereotactic biopsy. The guidance is achieved by creating a coordinate system using two mammography images at a specific angle between them. The sampling needle is then directed toward the finding using computerized calculations.
When a suspicious finding is detected in magnetic resonance imaging (MRI), it is common practice to return to ultrasound, even if a proper ultrasound examination was done before the MRI and was near it. Often, the ultrasound examination can identify the finding under guidance. Typically, small growths are discovered this way. If an ultrasound does not show the finding, a biopsy can be performed under MRI guidance.
Sampling Methods:
1. Fine-needle aspiration (FNA): This sampling is performed using a very thin needle that is inserted into the finding either under palpation or ultrasound guidance. The material obtained may contain cancerous cells. However, microscopic examination cannot always determine the type of growth since only a small part of the growth is sampled, and it may have different components in various areas. The accuracy of this test ranges from 90% to 98%, depending on the sampling method, the number of samples taken, and the expertise of the performing institute. FNA can also be used for sampling suspicious lymph nodes during palpation or ultrasound.
2. Core Needle Biopsy: This involves a thicker needle that takes a cylindrical sample of tissue, providing information about the type and characteristics of the growth (e.g., estrogen and progesterone receptors). The biopsy is performed under local anesthesia. A positive result is unequivocal, but the characteristics of the growth may not necessarily match the full information (obtained after surgery) since only a small part of the growth is sampled, and the growth itself may consist of different components in different areas. This biopsy can be performed under manual, ultrasound, or stereotactic guidance and is mainly used for sampling calcifications.
3. Vacuum-assisted biopsy: In this method, a larger needle is used, and a vacuum sucks part of the suspicious tissue into the needle chamber. The internal blade cuts the tissue sample, allowing multiple samples to be obtained without removing and reinserting the needle. The device can be used under manual or ultrasound guidance, but its primary use is under stereotactic guidance for sampling calcifications.
4. Surgical biopsy: In cases where the suspicion of growth is significant, and percutaneous biopsies (tissue samples) do not diagnose the growth, surgical biopsy may be required. This procedure involves removing the finding and examining it under a microscope. If the results of the surgical biopsy are positive for cancer, it is highly likely to be accurate (95% in skilled centers). However, this biopsy is not performed based solely on a positive result from a percutaneous biopsy. It can also be used for sampling suspicious lymph nodes during palpation or ultrasound.
In cases where the degree of suspicion is significant, and percutaneous biopsies do not diagnose the growth, a surgical biopsy may be required. This procedure involves removing the finding and examining it under a microscope. If the results of the surgical biopsy are positive for cancer, it is highly likely to be accurate (95% in skilled centers). However, this biopsy is not performed based solely on a positive result from a percutaneous biopsy. It can also be used for sampling suspicious lymph nodes during palpation or ultrasound.