Lymphatic mapping for melanomas of the upper extremity

Radioguided sentinel lymph node biopsy in patients with malignant cutaneous melanoma: the nuclear medicine contribution

As for other solid tumors, malignant cutaneous melanoma drains in a logical way through the lymphatic system, from the first to subsequent levels. Therefore, the first lymph node encountered (the sentinel node) will most likely be the first to be affected by metastasis, and a negative sentinel node makes it highly unlikely that other nodes in the same lymphatic basin are affected. Sentinel lymph node biopsy distinguishes patients without nodal metastases, who can avoid nodal basin dissection with its associated risk of lymphedema, and those with metastatic involvement who might benefit from additional therapy. This procedure represents a significant advantage as a minimally invasive procedure, considering that only an average 20% of melanoma patients with Breslow thickness between 1.5 and 4 mm harbour metastasis in their sentinel node(s) and are therefore candidates to elective lymph node dissection procedures. The cells that originate cutaneous melanomas are located between dermis and epidermis, a zone that drains to the inner lymphatic network in the reticular dermis, in turn to larger collecting lymphatics in subcutis. Therefore, the optimal modality of interstitial administration of radiocolloids for lymphoscintigraphy and subsequent radioguided sentinel lymph node biopsy is through intradermal/subdermal injection. (99m)Tc-labeled colloids in various size ranges are equally adequate for radioguided sentinel lymph node biopsy in patients with cutaneous melanoma, depending on local experience and availability. For melanomas located in the midline area of the head, neck, and trunk, particular consideration should be given to ambiguous lymphatic drainage, which frequently requires interstitial administration virtually all around the tumor or surgical scar from prior excision of the melanoma. Lymphoscintigraphy is an essential part of radioguided sentinel lymph node biopsy because images are used to direct the surgeon to the sites of the node(s). The sentinel lymph node should have a significantly higher count than that of background (at least 10:1 intraoperatively). After removal of the sentinel node, the surgical bed must be reexamined to ensure that all radioactive sites are identified and removed for analysis. The success rate of radioguidance in localizing the sentinel lymph node in melanoma patients is about 98% in institutions where a high number of procedures are performed, approaching 99% when combined with the vital blue dye technique. The procedure is becoming the standard of care for patients with cutaneous melanoma because of its high prognostic value that has led to include the procedure in the most recent version of the TNM staging system.

[Marking the route of lymphatic spread of melanoma and sentinel lymph node biopsy]

<zakljucak> Biopsija limfnih zlezda strazara je postupak koji, uz relativno nizak morbiditet, daje precizne podatke o stanju regionalnog limfonodalnog basena bolesnika sa melanomom koze. Stanje regionalnih limfnih zlezda je kljucni prognosticki parametar, veoma bitan za planiranje daljeg lecenja. Za uspesnu identifikaciju i histopatolosku obradu SLN neophodna je saradnja hirurga, nuklearnog radiologa i histopatologa. Dijagnostikovanjem okultnih metastaza u regionalnim limfnim zlezdama identifikuju se bolesnici kojima treba uciniti kompletnu limfonododisekciju, kao i oni koji mogu imati koristi od primene adjuvantne antitumorske terapije. Uvodjenjem ovog postupka dilema izvodjenja ili ne ELND vise ne postoji. Tehnicki i kadrovski zahtevi medjutim, jos uvek je ne svrstavaju u rutinske standardne postupke u lecenju melanoma. Pronalazenje mikrometastaza u regionalnim limfnim zlezdama menja stadijum bolesti u kome je bolesnik do tada bio (migracija stadijuma, Will Rogers fenomen). Novim klasifikacionim sistemom definise se klinicki i patoloski stadijum bolesti (14, 114). Ukoliko su regionalni limfonodusi ispitivani klinickim i/ili radioloskim postupcima, moze se govoriti o klinickom stadijumu bolesti. Za odredjivanje patoloskog stadijuma neophodna je histoloska evaluacija limfnih zlezda dobijenih bilo selektivnom bilo elektivnom limfadenektomijom. SLNB se smatra jednim od najvecih napredaka u terapiji melanoma u zadnjoj deceniji XX veka (4, 111). Ocekuje se da ce postati standard u lecenju bolesnika sa klinicki negativnim limfnim zlezdama (99, 111, 112), posebno sa usvajanjem novog sistema za odredjivanje stadijuma koze (14, 114, 115).

Pathologic analysis of the sentinel lymph node

The development of the sentinel lymph node concept has had a revolutionary effect on the way radical cancer surgery is viewed. The selective excision of the sentinel node alone has been proposed as an alternative to complete regional lymphadenectomy. This article addresses the sentinel lymph node hypothesis and the role of pathologic analysis, radiation safety, intraoperative and postoperative assessment, pathologic analysis in prognosis, and polymerase chain reaction-based studies.