NEW YORK Although melanoma is known for metastasizing to various sites, the most common site of metastasis is the locoregional lymph nodes, according to Dr. Richard Shapiro. They can be large and bulky or microscopic.
In a review of the literature on sentinel lymph node biopsy (SNLB), he noted that lymph node metastasis has been greatly associated with a decline in patient survival. However, "patients with nonpalpable, microscopic melanoma metastases tend to do much better than the patients who present with palpable metastases," he said at the American Academy of Dermatology's Academy 2007 meeting.
The thickness of a melanoma is key to its likelihood of having metastasized, he said. Thin melanomasless than 0.76 mm in Breslow thicknesshave a very small chance of having regional or distant metastases. However, patients with thick melanomas4 mm or greater often have distant metastatic disease at presentation, said Dr. Shapiro of New York University, New York.
"It's the patients with so-called intermediate thickness lesionsthat are approximately 0.76 mm to 4 mm thickthat have a much higher likelihood of having microscopic metastatic disease when they present than they do with having distant metastases. And so it would make sense in that intermediate thickness melanoma group to remove the lymph nodes in those patients and to see if we can decrease recurrence and increase survival."
Approximately 100 retrospective trials in the last 50 years have assessed associations between melanoma thickness and survival, with the only survival advantage seen in the patients with intermediate-thickness melanomas. However, prospective trials have found no survival advantage to elective lymph node dissection in patients with no clinical evidence of metastatic melanoma in the regional lymph nodes at presentation, Dr. Shapiro noted.
"Right now I would say the ideal candidate to undergo sentinel lymph node mapping and biopsy is the patient with a primary cutaneous melanoma 1 mm thick or greater, with no clinical evidence of regional lymph node metastases and in a patient where successful scintigraphy preoperatively can be performed and demonstrate regional lymph node draining," he said.