The tumor biology of melanoma nodal metastases

Approximately 20 per cent of melanomas greater than 0.76 mm in thickness will metastasize to the regional lymph nodes if treated with wide local excision alone (WLE). Elective lymph node dissection (ELND) is associated with significant morbidity, which includes lymphedema, wound complications, and paresthesias of the extremity. An alternative operative approach uses selective lymphadenectomy with the identification of the sentinel node, defined as the first node in the lymphatic basin that drains the primary cutaneous site. This study consisted of 132 patients with melanomas greater than 0.76 mm. One hundred nine patients (83%) had histologic negative sentinel nodes, and 23 patients (17%) had one or more sentinel nodes positive for disease. In patients with metastatic disease, 30/35 (86%) sentinel nodes were positive, and 25/357 (7%) nonsentinel nodes were positive (P < 0.001). In 18 patients (78%) of the 23 patients with metastatic disease, the sentinel node was the only node positive, strongly suggesting that there is an orderly progression of metastases. Two patients developed metastatic nodal disease after removal of a negative sentinel node (false negative rate = 1.5). The mean follow-up was 1 year. Sentinel node histology reflects the histology of the remainder of the nodes in the lymphatic basin and "skip" metastases, defined as a negative sentinel node but positive nodes higher in the regional chain positive for metastases or an axillary recurrence after a negative sentinel node biopsy, are rare for malignant melanoma. Harvesting the sentinel node in patients with intermediate or greater thickness melanoma will, therefore, identify a subset of patients with metastatic disease who have the most to benefit from a complete node dissection. This surgical approach allows for complete pathological staging and therapeutic management of patients while significantly reducing expense and overall morbidity.