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The sentinel lymph node biopsy is an exciting novel
approach to breast cancer treatment. The sentinel or “gate-keeper” lymph
node is the first lymph node in the drainage path of your breast
cancer. Using sophisticated localization techniques, our surgeons who
are trained to identify the sentinel nodes will remove the targeted
lymph node tissue and submit it immediately to the Surgical Pathology
Laboratory. The surgical pathologist will delicately dissect the lymph
node tissue and thinly slice the lymph node tissue with a razor blade.
The surgical pathologist will examine the sliced tissue for any tumor
deposits. If a tumor deposit is not detected, the surgical pathologist
will sample the lymph node tissue by performing a “touch preparation”.
In this procedure, the pathologist touches a clean glass slide to the
tissue resulting in thousands of cells adhering to the slide. The slide
is fixed in alcohol, stained, and then examined under a microscope.
Using this method, a pathologist can detect microscopic tumor deposits
that can not be seen with the naked eye. If a tumor deposit is
identified, the pathologist will perform a frozen section in addition to
the touch preparation. Frozen section is a technique that allows thin
sections of tissue to be examined under a microcope to confirm the
presence of a tumor deposit. In this technique, the pathogist freezes a
thin slice of tissue at minus 20 degrees celcius and rapidly stains the
tissue with metachromatic dyes referred to as hematoxylin and eosin. The
process takes approximately 10 minutes to perform.
Once the immediate evaluation for tumor deposits
has been made and reported to your surgeon, the tissue is fixed in
formalin for several hours, processed through a number of steps that
optimize tissue preservation, and embedded in paraffin (wax). A
histotechnologist who is trained and certified to handle these specimens
will mount the specimen on a tissue cutter referred to as a microtome
and cut multiple micron thin slices at various levels in an effort to
detect any tumor deposits. These thin slices referred to as sections are
examined by the pathologist with a microcope that allows the tissue to
be magnified 400 to 500 times. If the pathologist does not detect tumor
deposits at this point, a special stain called cytokeratin is ordered.
This is a monoclonal antibody stain that targets a protein produced by
breast cancers. This stain is exquisitely sensitive and can detect as
little as one or two tumor cells.
The sentinel lymph node procedure is an extremely
accurate and sensitive method to detect and stage breast cancer. Using
these methods of detection, surgical pathologists can detect or rule out
metastatic disease in 90-100% of patients [ref 1 and 2].
References
1) Morgan A et al. Initial experience in a community hospital
with sentinel lymph node mapping and biopsy for evaluation of axillary
lymph node status in palpable invasive breast cancer. Journal of
Surgical Oncology. 72(1):24-30, 1999 September
2) Van Diest PJ et al. Reliability of intraoperative frozen
section and imprint cytological investigation of sentinel lymph nodes in
breast cancer. Histopathology 35(1): 14-18, 1999 Jul
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