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
A sentinel node is the hypothetical first node or group of nodes that receive lymph drainage from a tumor.
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.
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
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.
The inguinal lymph nodes should not be clinically suspicious for metastasis.
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.
Patients with vulva melanomas are also good candidates for sentinel node removal.
IMAGING AND OTHER DIAGNOSTICS
Standard imaging has not been successful in identifying metastases in groin lymph nodes. PET/CT, MRI, and CT have not been accurate.
PREOPERATIVE PLANNING
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.
Frozen section for the sentinel node should be available.
SURGICAL MANAGEMENT
Positioning
Low lithotomy position with leg support stirrups.
PROCEDURES AND TECHNIQUES
Procedures and Techniques
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).
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).
The surgeon identifies the hot spots with the gamma probe.
The incision is made down to the identified node (Tech Fig. 4.3).
If blue dye has been used it may identify the node as well.
The hottest node is removed and scanned again off the field.
The probe is used to find other nodes (Tech Fig. 4.4).
All nodes with a count five times greater than the background should be removed.
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