Update on lymphatic mapping and sentinel node biopsy in the management of patients with melanocytic tumours

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Abstract
To communicate best practices for sentinel lymph node evaluation and assessment of prognosis for patients with melanoma. Description and justification of approaches derive from experience with management of more than 2000 melanoma patients evaluated by lymphatic mapping and sentinel node biopsy (LMSNB). Pathologists, by detecting blue dye or carbon particles or alterations in nodal cell populations should attempt to confirm that a node submitted as sentinel is truly sentinel. Pathologists must adequately sample the node by examining multiple tissue sections and determine the presence or absence of metastatic melanoma using sections stained by H&E and immunocytochemistry. Approximately 20% of patients have melanoma in the sentinel node (SN) and accurate evaluation of SN tumour status is the most precise technique for staging clinically localised cutaneous melanoma. The remaining non-sentinel nodes (NSN) in the basin are tumour-free in 67% of patients with melanoma in the SN. Breslow thickness of the primary, the area of tumour in the SN (relative to total nodal area) and density of dendritic leukocytes in the SN paracortex (factors that are combinable in prognostic algorithms) predict metastases in the NSN and the likelihood of recurrence and melanoma-specific death. Careful pathological analysis is essential to determine the presence or absence of metastatic melanoma in sentinel nodes, findings that indicate whether completion lymphadenectomy is required. Quantitative analysis of the primary melanoma and the amount of tumour in the sentinel node, with evaluation of the dendritic cells in that node, provide invaluable information that predicts non-sentinel node tumour status with increased accuracy and the likelihood of future recurrence and death from melanoma. While these activities require considerable effort from pathologists, their clinical impact justifies the increased workload.