Technical Details of Intraoperative Lymphatic Mapping for Early Stage Melanoma

TLDR

Melanoma metastasizes first through lymphatics to regional nodes, yet routine lymphadenectomy in clinical stage I patients is controversial because most lack nodal disease, derive little benefit, and risk postoperative limb edema. The authors developed a vital‑dye technique that intraoperatively identifies the sentinel lymph node—the nearest node along the primary tumor’s drainage pathway—for immediate pathological examination of occult melanoma cells. In 194 of 237 lymphatic basins, sentinel nodes were located and metastases were found in 40 specimens (21 % overall, 12 % by routine H&E and 9 % by IHC), with 47 of 259 sentinel nodes (18 %) harboring disease and a false‑negative rate below 1 %, demonstrating high‑accuracy detection of nodal metastases in early‑stage melanoma.

Abstract

The initial route of metastases in most patients with melanoma is via the lymphatics to the regional nodes. However, routine lymphadenectomy for patients with clinical stage I melanoma remains controversial because most of these patients do not have nodal metastases, are unlikely to benefit from the operation, and may suffer troublesome postoperative edema of the limbs. A new procedure was developed using vital dyes that permits intraoperative identification of the sentinel lymph node, the lymph node nearest the site of the primary melanoma, on the direct drainage pathway. The most likely site of early metastases, the sentinel node can be removed for immediate intraoperative study to identify clinically occult melanoma cells. We successfully identified the sentinel node(s) in 194 of 237 lymphatic basins and detected metastases in 40 specimens (21%) on examination of routine hematoxylin-eosin-stained slides (12%) or exclusively in immunohistochemically stained preparations (9%). Metastases were present in 47 (18%) of 259 sentinel nodes, while nonsentinel nodes were the sole site of metastasis in only two of 3079 nodes from 194 lymphadenectomy specimens that had an identifiable sentinel node, a false-negative rate of less than 1%. Thus, this technique identifies, with a high degree of accuracy, patients with early stage melanoma who have nodal metastases and are likely to benefit from radical lymphadenectomy.