for further surgical management of the nodal basins. The evolution of the sentinel node concept began in 1955 when the concept of the first echelon node was introduced. Gould coined the term “sentinel node” in 1960 and the first successful sentinel node biopsy was performed in 1977 in a patient with penile cancer. The concept was revived by Morton in 1992 and applied to N0 melanoma. Since then, it has become the standard for treatment of N0 melanoma and breast cancer.
Application of sentinel node biopsy to the head and neck has not been as feasible as its application to the trunk and extremities. O’Brien delineated four drawbacks to its application to the head and neck:
It is difficult to visualize lymphatic channels using lymphoscintigraphy because of proximity to the injection site.
The radiotracer travels fast in the lymphatic vessels.
If more than one node is visible, it can be difficult to distinguish first echelon nodes from second-echelon nodes.
The SLN may be small and not easily accessible (eg, in the parotid gland). Sentinel lymph node biopsy (SLNB) has been successfully performed in patients with
cutaneous malignancies of the head and neck. Since 1996 several investigators have displayed the feasibility of SLNB in squamous cell carcinoma of the pharynx and oral cavity. The first reported use was in the hypopharynx. Since then more investigators have focused on N0 disease for patients with oral cavity SCCA. There are multiple small case series that display the feasibility of SLNB in these patients although no there are no standardized techniques between institutions. All the series compare the efficacy of pre op lymphoscintigraphy, intraoperative localization with the gamma probe with or without blue dye and the results of final pathology for the completed neck dissection specimens.
Pre operative techniques for SLNB include injection with a radiotracer. The tracer has to be able to be taken up by the lymphatics but large enough to remain in them to make detection possible. Technetium is the most commonly used radiotracer. It is injected submucosally in quadrants surrounding the tumor one day prior to surgery. The total dose injected does not affect the ability to locate sentinel nodes on lymphoscintigraphy according to a recent meta-analysis. The use of local anesthetic is debated because some investigators feel it may affect tracer uptake. Spillage of the tracer should be avoided in the oral cavity at time of injection.
About 45 – 60 minutes following tracer injection the patient should undergo dynamic lymphoscintigraphy followed by static lymphoscintigraphy. Typically a sentinel node can be seen within fifteen minutes during the dynamic imaging. AP, lateral and oblique static images help confirm the dynamic imaging and delayed static images reveal sentinel nodes when the dynamic images are non-revealing. Using a cobalt pencil to mark landmarks like the mandible, chin, cricoid and sternal notch also aid in localizing the node.
Not all investigators use blue dye to help locate sentinel nodes. Those that do use it inject the dye about 20 minutes prior to surgery. Intraoperative gamma probes are used in conjunction with the dye to localize the sentinel nodes. A distant site on the patient is scanned to record the background levels. Then the operative bed is inspected with the probe and high signal nodes