Core Biopsies: Size, volume, and other considerations
A biopsy will usually be requested when something suspicious appears on the mammogram, or when a palpable lump has been detected. A biopsy sample is sent to the pathologist for a histological evaluation. One of the first goals of the histological evaluation is to determine if the suspicious element is cancer, or some other unrelated or possibly benign condition.
I just want to let you know that I have created a newer version of this page with more up-to-date information on Core Biopsies. However, even though this page is a little “old” and “out-dated”, it still has very great material and I would still use it.
However, when the mammogram is highly suggestive of either invasive cancer or DCIS, there are then four main objectives for a biopsy. They are; to establish the histological grade, to evaluate the hormonal receptors, to study the sentinel node, and to help the surgeon plan for a ‘one step‘ surgery. In other words, if mammography is highly suggestive of breast cancer, a ‘larger‘ biopsy sample or possibly multiple samples may be requested to learn as much as possible about the tumor, as quickly as possible.
Percutaneous Biopsies: Fine needle and core
A percutaneous biopsy is simply one that is done ‘through the skin‘, with a needle, as opposed to an actual surgical excision. There are different sizes/diameters of needles used. A ‘fine needle aspiration‘ , where just a small tissue sample is collected from a a lesion , is typically done with 21 or 20 gauge needle. A ‘core‘ biopsy is a special needle of a larger ‘gauge‘, that is able to get a “core” of tissue inside the needle.. like a core sample of a glacier. Core biopsies are done with 18 or 16 or 14 gauge needles (the higher numbers are ‘smaller‘ needles).
A relatively new procedure called a ‘vacuum assisted‘ biopsy is also done with an 11 gauge needle, and a ‘vacuum assisted device‘ or VAD such as the ‘Mammotome‘ ® which seems to get a larger tumor sample with less attempts. An 11 gauge probe paired with a vacuum-assisted device typically picks up 94 mg with each core sample. The 14 gauge needle with vacuum assistance typically picks up 37 mg, but only 17 mg when paired with an automated biopsy gun.
Vacuum assisted device, or VAD, useful for intermediate categories
The VAD or vacuum assisted device is a more costly and invasive way to get a tissue sample, but it is a very good technique for indeterminate lesions. It is an excellent method where there are microcalcifications involved, and is most frequently used in a suspected BI-RADS 4 scenario.
Biopsy of microcalcifications using a VAD
Usually a pathologist will want to obtain about 1.5 grams if tissue in total when using a vacuum assisted device. So, about 10-15 specimens are usually taken, and an 11 guage probe is usually used to increase accuracy and diagnostic yield. VAD biopsies are able to retrieve more microcalcifications, which improves the correlation between radiologic (X-ray) and histologic (microscopic evaluation) analysis.
The biopsy sample given in the image below shows a number of microcalcifications and columnar cells. This breast lesion is probably still benign. There are not yet enough cells accumulating in the duct wall to call it malignant, but it may be atypical hyperplasia.
Minimum sample recommendations for core biopsies
If the pathologist wishes to examine microcalcifications, then the minimal sample recommended is 10 specimens with the 14 gauge needle. If a mass is being tested, then the recommended frequency is 5 specimens with stereo tactic guidance, or just 4 with ultrasound guidance. Core samples tend to be about 17-20 mg each with a 14 gauge needle. With a 14 gauge probe and a VAD, the samples are about 37-40 mg each, and with an 11 gauge VAD samples are as large as 94 mg each (but you don’t need as many).
Less invasive methods are preferred when there may be epithelial displacement
If a lesions is BI-RADS category 5, or ‘highly suspicious of malignancy‘ , the use of the VAD is a bit controversial. There is the possibility of unintentional spread of potentially malignant cells via ‘epithelial displacement‘, but in a controlled clinical setting and with proper protocols, there should be no problem.
On the other hand, there is an inherent advantage to using the VAD in that the probe is introduced only once, while core biopsies have to introduce the needle several times. Vacuum Assisted Device biopsies are much less likely to result in histological underestimation of breast carcinoma, when compared to core biopsies.
Why not use a VAD all the time, if is less invasive and more reliable?
The problem with vacuum assisted biopsies, is that the government only pays a certain fee for a percutaneous breast biopsy with a needle. The fee is too small to pay for the vacuum assisted variety of equipment, which is much more expensive than a core needle. Hence, any department would be losing money if they did VA biopsies with government fees. So, most hospitals stick with percutaneous needle biopsies for breast cancer screening and staging, when the tumor is thought to be of an intermediate grade or lower.
For further reading, I suggest you visit this page on the sentinel lymph node biopsy technique, as well as this page for the progression and stages of breast cancer.
- The mammotone is a registered and trademarked product belonging to Ethicon Endo-Surgery, Inc. 2008. For more information , visit their homepage at www.breastbiopsy.com.
- American College of Radiology: A Module for Mammography
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