Core Biopsy of the Breast: Size, volume and other considerations
A doctor will usually request a core biopsy when something suspicious appears on the mammogram, or when a palpable lump is present.
Next, the 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 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I just want to let you know that I have created a newer version of this page with more up-to-date information on all types of biopsies, including core biopsies.
However, when the mammogram results are highly suggestive of either invasive cancer or DCIS, there are then four main objectives for a biopsy. These are to establish the:-
- Histological grade of the tumor
- Hormonal receptor status of the tumor
- Sentinel lymph node status
- Plans for breast surgery
In other words, if mammography is highly suggestive of breast cancer, a ‘larger’ biopsy sample or possibly multiple samples may be necessary. This is to enable doctors to learn as much as possible about the tumor, as soon as possible.
Percutaneous Biopsies: Fine Needle and Core Biopsy
A percutaneous biopsy is simply means that the surgeon takes the sample ‘through the skin’ with a needle, in opposition to an actual surgical excision.
So, the surgeons will use different sizes and diameters of needles. In a fine needle aspiration (FNA) surgeons take just a small tissue sample from the lesion. So, with FNA, the surgeon will typically use a 21 or 20 gauge needle.
A core biopsy is simply 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. Surgeons perform a core biopsy with an 18 16 or 14 gauge needle (the higher the number the ‘smaller‘ the needles).
A relatively new procedure, the ‘vacuum assisted’ biopsy is also uses an 11 gauge needle and a ‘vacuum assisted device’ or VAD. For example, the ‘Mammotome‘ ® which seems to get a larger tumor sample with less attempts.
An 11 gauge probe together 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. However, the sample size drops to only 17 mg when surgeons use an automated biopsy gun.
Vacuum Assisted Device (VAD) is useful for intermediate categories
The Vacuum Assisted Device (VAD) is a more costly and invasive way to get a tissue sample. However, it is a very good technique for indeterminate lesions. So, the VAD is an excellent method where there are microcalcifications present, and is most frequently used if there is suspicion of a BI-RADS 4 scenario.
Biopsy of microcalcifications using a VAD
Usually a pathologist will want to obtain about 1.5 grams of tissue in total when using a Vacuum Assisted Device. So, the surgeon will usually try and take about 10 to 15 specimens using an 11 gauge needle. This method increases accuracy and diagnostic yield.
VAD biopsies are able to retrieve more microcalcifications. This improves the correlation between radiologic (X-ray) and histologic (microscopic evaluation) analysis.
The biopsy sample 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 recommended sample is 10 specimens with the 14 gauge needle.
If a mass is present, then the recommendations are 5 specimens with stereo tactic guidance, or just 4 with ultrasound guidance. Core samples tend to be about 17 to 20 mg each with a 14 gauge needle. With a 14 gauge probe and a VAD, the samples are about 37 to 40 mg each using an 11 gauge. However, VAD samples can be as large as 94 mg each (but you do not actually need this many).
Less Invasive Biopsy methods for Epithelial Displacement
If a lesion is a BI-RADS category 5 or highly suspicious of malignancy , the use of the VAD is a bit controversial. Firstly, there is the possibility of unintentional spread of potentially malignant cells via ‘epithelial displacement’. However, in a professional clinical setting with proper protocols, this should not be a problem.
On the other hand, the advantage of using the VAD is that the surgeon introduces the probe only once. In contrast, 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 in comparison to core biopsies.
Why not use a VAD all the time, if it 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. Indeed, VAD is much more expensive than a core needle biopsy.
Hence, any department would be losing money if they perform VAD biopsies with government fees. So, most hospitals stick with percutaneous needle biopsies for breast cancer screening and staging, when the specialists suspects the tumor 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.
- Becker L, Taves D, McCurdy L, Muscedere G, Karlik S, Ward S. (2001) Stereotactic core biopsy of breast microcalcifications: comparison of film versus digital mammography, both using an add-on unit. AJR Am J Roentgenol. (Dec. 2001) 177(6):1451-7. https://www.ncbi.nlm.nih.gov/pubmed/11717106
- Berner A, Davidson B, Sigstad E. (et al). (2003) Fine-needle aspiration cytology vs. core biopsy in the diagnosis of breast lesions. Diagn Cytopathol (2003). 29, 344–348 https://www.ncbi.nlm.nih.gov/pubmed/14648793