Sentinel Nodes for Vulva Cancer
Kenneth D. Hatch
GENERAL PRINCIPLES
The major morbidity from complete inguinal-femoral node dissection is lower-extremity lymphedema. This may be accompanied by recurrent lymphangitis. This has heightened the interest in developing the concept of sentinel lymph node detection.
Definition
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A sentinel node is the hypothetical first node or group of nodes that receive lymph drainage from a tumor.
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The node or nodes are identified by injecting radioactive technetium-99m (99mTc) or visible blue dyes around the tumor margin and then surgically removing the identified nodes.
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If the sentinel node is negative the patient could then be spared the complications of a larger operation that would remove all of the regional lymph nodes.
Anatomic Considerations
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The ideal candidate is a squamous cell cancer less than 4 cm in size that is 2 cm or more from the midline and unifocal.
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The inguinal lymph nodes should not be clinically suspicious for metastasis.
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If the tumor is in the midline then sentinel nodes must be identified on both sides. In the absence of a sentinel node then an inguinofemoral node dissection should be performed.
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Patients with vulva melanomas are also good candidates for sentinel node removal.
IMAGING AND OTHER DIAGNOSTICS
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Standard imaging has not been successful in identifying metastases in groin lymph nodes. PET/CT, MRI, and CT have not been accurate.
PREOPERATIVE PLANNING
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The radioactive injections are placed in the nuclear medicine department 2 hours before the procedure and a lymphoscintigram or SPECT-CT scan is performed. An image of the sentinel node is obtained for the surgeon. A handheld gamma probe must be available for intraoperative assessment of the gamma count.
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Frozen section for the sentinel node should be available.
SURGICAL MANAGEMENT
Positioning
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Low lithotomy position with leg support stirrups.
PROCEDURES AND TECHNIQUES
Procedures and Techniques
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Two hours before the surgery the patient reports to nuclear medicine where the 99mTc-labeled microsulfur colloid is injected. It is placed at four sites around the edges of the tumor (Tech Fig. 4.1).
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If isosulfan blue dye is to be used also this will be injected after the patient is prepped and draped in the operative room for the surgery (Tech Fig. 4.2).
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The surgeon identifies the hot spots with the gamma probe.
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The incision is made down to the identified node (Tech Fig. 4.3).
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If blue dye has been used it may identify the node as well.
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The hottest node is removed and scanned again off the field.
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The probe is used to find other nodes (Tech Fig. 4.4).
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All nodes with a count five times greater than the background should be removed.
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