Sentinel Lymph Node Biopsy for Melanomaby Dr. Craig L. Slingluff, Jr., MD Rationale The rationale for sentinel lymph node biopsy in melanoma patients is that the lymphatic drainage for the skin site of a primary cutaneous melanoma can be mapped routinely using standard lymphoscintigraphy techniques which have been time tested over the past several decades. The standard approach for this has been intradermal injection of Technetium-99 labeled sulfur colloid. Standard gamma camera imaging after such injection permits identification of the draining nodal basin or basins usually within a matter of minutes. Within the nodal basin or basins identified by lymphoscintigraphy, one or two lymph nodes typically can be identified on the lymphoscintigram as the first sentinel node(s) draining the tumor site. A handheld gamma probe is used in the operating room to identify and to resect the sentinel node(s), using the Technitium label as a guide. Injection of vital blue dye (Isosulfan blue) intradermally may facilitate this node identification when needed. Procedure The procedure that we employ for sentinel lymph node biopsy involves the injection of unfiltered Tc-99 sulfur colloid intradermally at multiple sites around the melanoma itself or around the biopsy scar. It is preferable that this be done before a wide excision is performed, but we have performed it after wide excision, with good results. Before doing the injection, we apply an ointment to the skin which provides some local anesthesia to make the injection less painful. Once the injection is performed, the patient is placed on an imaging table for evaluation with the gamma camera. This is done in the Nuclear Medicine suite under the guidance. At that time, we correlate findings from the gamma camera with those found with the handheld gamma probe. Once we have evaluated the nodal drainage, the patient is taken to the operating room where the location of sentinel node(s) is further confirmed and determined using the handheld probe. A small incision is made over the identified hot spot. The incision usually is limited to about 2-3 cm. We can often perform this under local anesthesia although some patients prefer a general anesthetic. The sentinel node(s) are identified and resected and sent for a standard histologic evaluation. Most of these patients have not had a wide excision prior to this procedure, which is the preferred situation. Thus, a wide excision is performed on the same day as the sentinel node biopsy. This is an outpatient procedure, and the morbidity is quite small, as would be expected. Results of Sentinel Lymph Node Biopsy for Melanoma The reported experience with sentinel node biopsy approaches for melanoma has been that the sentinel node can be identified successfully in well over 90% of cases. Our experience has been that the sentinel node(s) can be identified successfully in virtually all cases. If melanoma cells are found in the sentinel node, we routinely recommend surgical clearance of all the nodes in that lymph node basin (complete node dissection). Our experience matches that reported by others, that about 15% of patients have additional nodes with melanoma in them , in these situations, though there may be some patients who have microscopic melanoma cell deposits that are so small that they are not detectable with routine evaluation of those nodes. When the sentinel node is negative, it has about 98-99% negative predictive value that the entire nodal basis is negative. Patients who have been followed for several years after a negative sentinel node biopsy do have risk of recurrence in that nodal basin that is in the range of 3-4%. These numbers are actually quite similar to the likelihood of recurrence in a node basin after a standard elective lymph node dissection with negative nodes, as we reported in 1994 (Ann. Surg. 219: 120-130). Indications The indication for a sentinel lymph node biopsy for melanoma is a primary melanoma 1.0 mm thick or greater, in the absence of clinical evidence of metastatic disease in lymph nodes or other areas. Also, for patients with melanomas less than 1 mm thick, we recommend sentinel node biopsy if the melanoma is Clark level IV or greater, is ulcerated, or has a positive deep margin on biopsy. The reason for performing the node biopsy is to provide accurate staging. The benefits from this include the opportunity for patients to consider adjuvant therapy if nodes are positive. This is relevant in the setting of alfa-interferon being approved for clinical use. There also are some experimental immune therapy protocols that require that the patient either have a thick melanoma or positive nodes. For patients who are not candidates for adjuvant therapy, the indications for sentinel node biopsy are less clear, but there is some suggestion that regional control of spread to nodes may be achieved in some patients with sentinel node biopsy alone. These decision about use of sentinel node biopsy is affected by individual issues for each patient. We are happy to evaluate any patient for consideration of sentinel lymph node biopsy, and we perform it routinely. Any questions related to this procedure should be referred either to me or Karen Krosby, RN, through my secretary Denise Lindquist at 434-924-1730. I will also be happy to entertain or to respond to questions by e-mail cls8h@virginia.edu
Craig L. Slingluff, Jr., MD
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