NEW ORLEANSFor the majority of mammographically detected
invasive carcinomas with a mean size of 11 mm, stereotactic biopsy
obtained with larger gauge needles provides adequate material for
establishing a host of prognostic factors, said Michael D. Lagios,
MD, medical director of the Breast Cancer Consultation Service, St.
Marys Medical Center, San Francisco.
Stereotactic core technology can significantly reduce the morbidity,
anxiety, and costs of the evaluation, and can increase the target
accuracy for a biopsy of an occult lesion, compared with conventional
needle-directed open techniques, he said. However, some have
persistently questioned the equivalence of the diagnostic information
obtained by the newer method, Dr. Lagios said at the American Society
of Breast Disease annual meeting, cosponsored by the Ochsner Medical Foundation.
There are a few requirements for obtaining adequate diagnostic
information with this technique, he said. You need
excellent histopathology, excellent correlation between mammography
and pathology, and, he quipped, eyes attached to the
brain. You should also insist on minimal handling and prompt
fixation, and get six to eight levels of tissue, enough to reserve
some for other studies.
With proper technique, most stereotactic core biopsies using 14- or
11-gauge needles can establish histologic subtyping, grading, mitotic
indices, hormone receptor status, and occasionally lymphatic
invasion. It is usually possible to evaluate for HER2/neu, Ki-67, and
p53 as well as other biomarkers, and to determine ploidy and S-phase
fractionation by image cytometry.
Other significant prognostic featuresperitumoral lymphatic
invasion, extensive intraductal carcinoma, and multicentricity or
multifocalityare more easily documented with open biopsy or
subsequent lumpectomy specimens, he pointed out.
Estimating Tumor Size
Apart from nodal status, tumor size is the most important prognostic
factor for distant recurrence and for local recurrence when T3 is
reached. It would appear that stereotactic needle core technology
would be inherently less accurate when compared to size
determinations made by a pathologist measuring the excised lesion,
but this is not necessarily so, Dr. Lagios maintained.
Tumor size, for all its importance and for what intuitively
would appear to be a simple determination, is often erroneously
recorded, he pointed out. Pathologists often record the biopsy
size as the tumor size, overstate the tumor size by including the
invasive as well as adjacent areas of in situ disease, use
eyeball estimates, and make errors related to sectioning
Dr. Lagios cautioned that stereotactic biopsies obtained with the
Mammotome (a directional vacuum-assisted biopsy technique using a
thin rotating blade) are not designed to permit reliable measurement
of tumor size, although the size of the carcinoma within the core can
be measured by ocular micrometry.
In some cases, this will actually represent tumor size for T1a
and smaller T1b carcinomas, but, in all cases, correlation with
mammographic and/or son-ographic studies is required, he said.
Such estimates of tumor size based on correlation of imaging studies
with histology can markedly improve the accuracy of the tumor size
estimate, whether from a core biopsy or open excision. He pointed out
that size determination made by a pathologist should also be
correlated with preoperative studies, to avoid under- or
overestimating tumor size.
Measurement of tumor size in an open biopsy is certainly
easier, but in practice it is no more accurate than tumor size
estimated from correlated imaging studies and core pathology,
Dr. Lagios said that radial scars are an issue of concern with this
technique. They can be associated with synchronous atypical ductal
hyperplasia, ductal carcinoma in situ (DCIS), and lobular carcinoma
in situ, and can be misdiagnosed as invasive cancer (but can be
distinguished by immunohistochemical staining).
Stereotactic biopsy can clearly establish a diagnosis of a
radial scar, but it remains to be determined to what extent the
technique will sample associated atypical hyperplasia when
present, he said.