Developed as a way to sample mammographic abnormalities in a potentially
less invasive way, stereotactic technology has generated significant
controversy. Speaking at the 11th International Breast Cancer
Meeting in San Antonio earlier this year, Monica Morrow, MD, of
Northwestern University Medical School said that some overly-enthusiastic
radiologists consider stereotactic biopsy to be the technique
of choice for almost all mammographic abnormalities, whereas some
totally disinterested surgeons believe there is no real role for
this technique. Dr. Morrow believes that the appropriate position
lies somewhere between these two extremes--"stereotactic
biopsy is an appropriate technique for a selected group of mammographic
The purported advantages of stereotactic biopsy include:
It can be performed rapidly
It is relatively painless
It avoids scarring, both externally (preserving the cosmetic appearance
of the breast), and internally (minimizing distortion at biopsy
sites on a mammogram).
Some maintain it is significantly less costly, but this may not
be completely accurate, Dr. Morrow said. In the larger context
of the treatment of breast cancer, some of the apparent cost savings
are lost, especially in cases where the stereotactic biopsy represents
an additional step.
Opponents of stereotactic biopsy say that it is often not useful
for treatment planning due to insufficient specimens, and false-negative/false-positive
The Beginnings: Fine Needle Aspiration
Fine-needle aspiration cytology was the initial stereotactic technique
available. In the literature, typical results of this procedure
yielded a sensitivity of 91%. Unfortunately, for a variety of
reasons, not the least of which is a lack of trained cytopathologists,
the use of aspiration cytology never became widespread. One problem
is the fact that aspiration cytology can identify a mammographic
abnormality as benign, but can't specify the type of lesion. Furthermore,
this procedure does not reliably distinguish invasive from in
situ carcinoma, a major difficulty in planning treatment. Finally,
any atypia on cytology requires biopsy, although only approximately
20% will actually be cancer.
Core Needle Breakthrough
With the development of core needles that fit into the stereotactic
biopsy holder, the technique became much more appealing, Dr. Morrow
said. As opposed to collecting a cytologic specimen, a core of
tissue for histopathologic examination was obtained. The results
of a core biopsy (confirmed by open surgical biopsy) generally
indicate a sensitivity in the upper 90% range.
One of the technical factors affecting the outcome of a core biopsy
is needle size, with larger needles (commonly 14 gauge) providing
better results. The number of specimens taken also influences
the results. Many investigators are obtaining 10 cores as a sampling
procedure. To confirm the presence of calcification when this
is the indication for biopsy, the core specimen should undergo
x-ray. Also, whether or not lobular carcinoma in situ is classified
as a malignancy will influence sensitivity.
Proponents of stereotactic core biopsy claim that it renders a
definitive diagnosis of benign abnormalities, eliminates the false-positive
results seen with cytology due to atypia, distinguishes invasive
from in situ carcinoma, and enables surgeons to perform a definitive
operation armed with a diagnosis of cancer. However, many of these
claims are debatable, Dr. Morrow said.
A review of the literature indicates that a core biopsy correctly
diagnosed ductal carcinoma in situ in only 70% of cases. (All
of the core biopsies were confirmed surgically.) Based on this
limited information, it appears that a core biopsy's ability to
reliably identify ductal carcinoma in situ may be considerably
less than that reported for invasive carcinoma.
Furthermore, the information obtained from a core biopsy does
not necessarily correlate with intraoperative findings. Although
ductal carcinoma in situ was detected using optimal core technique
(a mean number of core samplings of seven per case with a large-gauge
needle) in a study of 82 cases of cancer, 10% of the time invasive
cancer that was not found by the biopsy core was identified on
open biopsy. In another 6% of cases, when simple invasive cancer
was identified on the biopsy core, an extensive intraductal component
was found intraoperatively. In essence, there have been some difficulties
with the pathologic information obtained from the core biopsy
and the ability to sample certain breast lesions.
Although one of the apparent advantages of a core biopsy is the
avoidance of sampling the atypias seen with cytology, many of
the atypical hyperplasias found on core biopsies actually were
found to be cancer on open biopsy.
The claim that being armed with a diagnosis of cancer somehow
helps a surgeon perform a lumpectomy more effectively has not
been substantiated, according to Dr. Morrow. In a series of 239
lumpectomies, 173 were performed as diagnostic procedures, and
66 were performed with a cancer diagnosis obtained via fine-needle
aspiration. The total positive margin rate was 5%. Therefore,
regardless of whether or not there was prior knowledge of cancer,
conservative lumpectomy as a single operation was effective 95%
of the time.
Although many of the alleged benefits of the core biopsy have
not been confirmed, it is a useful procedure in certain
cases. For example, to avoid open biopsy, Dr. Morrow may use core
biopsy for mammographic abnormalities that are suspicious but
deemed unlikely to be cancerous--lesions that, on mammography,
have perhaps a 2 to 20% risk of being malignant.
In summary, Dr. Morrow recommends stereotactic core needle biopsy
be considered for:
Relatively nonsuspicious breast lesions that are not clearly benign.
Women who are candidates for breast-conserving surgery but are
found to have other benign-appearing lesions elsewhere in the
Women who are candidates for mastectomy only.
As an alternative for women with significant co-morbidities such
that open biopsy would be more hazardous than usual.