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Sentinel Lymph Node Biopsy For Melanoma - Is There A Correlation Between Preoperative Lymphatic Mapping With Surgical Lymph Nodes Harvested?
Kristen A. Hudak, MD, Kevin E. Hudak, MS, MD, William W. Dzwierzynski, MD.
Medical College of Wisconsin, Milwaukee, WI, USA.

PURPOSE:
Nodal status is the most significant prognostic factor in melanoma, making adequate staging important. NCCN guidelines recommend sentinel lymph node biopsy for patients with thickness greater than 0.75mm or those with high-risk features such as ulceration, mitotic figures, lymphovascular invasive, or Clark’s level 4 or 5. Lymphoscintigraphy identifies lymphatic drainage patterns directing the physicians to the proper basin for removal of sentinel lymph nodes; however, it is often difficult for surgeons to understand how to utilize this data. No study has examined the relationship between lymphoscintigraphy and harvested nodes nor gamma probe counts and lymph node status.
METHODS:
262 patients were identified who underwent a sentinel lymph node biopsy for melanoma between 2001-2010. Clinico-pathologic and treatment information was collected. The number of lymph nodes and basins demonstrated on lymphoscintigraphy was compared to those found at surgery. Gamma probe counts were analyzed and compared.
RESULTS:
The median age was 54.5 (range 18-90) with 52.3% male Average Breslow depth was 2.0 mm (+-1.9 mm), 42% being shave biopsies with tumor present at the base. 99.6% of lymphoscintigraphy studies identified at least one basin, 80% showed only one (range 0-4). Lymphoscintigraphy identified an average of 1.5 (+-0.9) sentinel nodes and 31% with secondary node. Surgery excised on average 2.6 (+-1.4) nodes involving 1.2 (+-0.5) basins. 17.6% had a positive sentinel lymph node. There was no difference in the sum or average of gamma counts between positive and negative sentinel lymph node groups (p=0.2, p=0.5). When comparing lymphoscintigraphy and surgical excision, the correlation of lymphatic basins was r=0.67 and of lymph node numbers was r=0.33. Further analysis demonstrated that 32 patients had a positive sentinel lymph node among multiple removed nodes and removing only the hottest node from this group of patients would have missed the positive sentinel lymph node in three patients.
CONCLUSION:
Lymphoscintigraphy should be used to direct the surgeon to the proper lymphatic basins for a sentinel node procedure, however, the removal of lymph nodes must continue until the background count is less than 10%. The correlation of lymph node number identified on lymphoscintigraphy to surgical excision is weak. Gamma probe counts cannot be used to differentiate positive from negative lymph nodes and the positive lymph node is not always the hottest node from those removed.


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