Abstract

Although less common than other types of skin cancers, melanoma is accountable for the majority of skin cancer-related deaths. The standard management for patients with clinically negative nodes includes a sentinel lymph node (SLN) biopsy, which is commonly performed using a combination of radioactive tracer (Tc-99) and a blue dye (isosulfan or patent blue). There are numerous drawbacks associated with Tc-99 and blue dyes such as elevated costs, logistical challenges, and anaphylactic reactions among others. In recent years, near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) has emerged as a safe, effective, less costly, and more convenient alternative for the identification of SLNs in melanoma. We discuss the case of a 51-year-old man with melanoma in his left upper back. Two SLNs in the left axilla were successfully identified using NIR fluorescence. NIR fluorescence with ICG for SLN identification has proven to increase the sensitivity and accuracy when used in combination with lymphoscintigraphy.

Categories: Plastic Surgery, General Surgery
Keywords: near-infrared fluorescence imaging, melanoma, melanoma surgery, sentinel lymph node (sln)

Introduction

Melanoma represents only 3% of the skin cancers diagnosed each year; however, the disease is accountable for approximately 65% of skin cancer-related deaths [1]. Standard management for patients with clinically node-negative melanoma includes evaluation of regional lymph nodes by means of a sentinel lymph node (SLN) biopsy [2]. SLN biopsy is classically performed using a blue dye (isosulfan or patent blue) and a radioactive tracer (Technetium [Tc-99]) in order to identify the first lymph node or nodes that drain the primary melanoma site [2]. Despite advances in medical technology, pathologic analysis, and surgical techniques, false-negative SLN biopsy is still reported to occur in 13% of cases [3]. Furthermore, both Tc-99 and blue dyes have drawbacks such as possible supply shortages, logistical challenges between the operating room and radiology, staining in surrounding tissues, increased infectious complications, and potential skin necrosis [4]. Recently, near‐infrared (NIR) fluorescence imaging using indocyanine green (ICG) has emerged as an alternative method of SLN identification [5]. ICG is a water-soluble tricarbocyanine dye, which enables deep penetration into tissues, low light scattering, and tissue autofluorescence [6-8]. The use of ICG is relatively safe and non-toxic since the standard dose (2 mg/kg) is significantly lower than the lethal dose (80 mg/kg), with the exception of iodide reactions which are uncommon [6,8]. ICG offers potential advantages to radiotracer-based lymphoscintigraphy including an excellent safety profile, good tissue penetration, and real-time intraoperative imaging capabilities [5,8]. We discuss a case of melanoma for which two SLNs were identified using ICG NIR fluorescence imaging during surgical excision.

Case Presentation

A 51-year-old man with end-stage renal disease was referred to a dermatologist for full-body skin evaluation as part of a kidney transplant preoperative workup. The patient noted brown-colored nevi all over the body but none of them had acutely changed, itched, or bled. During the initial visit, three shave biopsies were taken from suspicious, discolored lesions on the left upper back and right shoulder. The biopsy from the left

upper back was positive for a 2.9-mm thick melanoma with a mitotic rate >1/mm2 and no ulceration. The lesion involved the deep and peripheral margins. The remaining two biopsies were positive for basal cell carcinoma. The patient was referred to the plastic surgery service for further management of melanoma.

Preoperatively, a positron emission topography (PET) scan showed no evidence of metastatic disease. The patient was given a preoperative injection of Tc-99 on the morning of surgery (Figure 1). Under general anesthesia, 0.1 mL of ICG was injected intradermally into the melanoma (Figure 2). A wide local excision of the melanoma was performed with cold knife in a rhomboid fashion. Our attention then turned to the left axilla. A gamma probe confirmed the presence of two SLNs as revealed by lymphoscintigram. An NIR light subsequently identified two hotspots on the skin, which corresponded to the two SLNs. We were able to identify the tract from the intra-lesion injection of ICG toward the left axilla and into two SLNs (Figures 3-6). These intraoperative findings were consistent with the gamma probe and preoperative lymphoscintigram findings. The SLNs were excised and sent to the pathologist (Figures 7, 8).

© Copyright 2021
Ferri et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 4.0., which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

How to cite this article

Ferri F, Montorfano L, Bordes S J, et al. (April 18, 2021) Near-Infrared Fluorescence Imaging for Sentinel Lymph Node Identification in Melanoma Surgery. Cureus 13(4): e14550. DOI 10.7759/cureus.14550

FIGURE 1

Figure 1
Preoperative lymphoscintigram

FIGURE 2

Figure 2
LN: lymph node
Peritumoral injection of indocyanine green

FIGURE 3

Figure 3
2021 Ferri et al. Cureus 13(4): e14550. DOI 10.7759/cureus.14550 2 of 7
Visualization of tumor under near-infrared light

FIGURE 4

Figure 4
Lymphatic mapping under near-infrared light

FIGURE 5

Figure 5
Identification of sentinel lymph node under near-infrared light

FIGURE 6

Figure 6
Dissection and excision of sentinel lymph node under near- infrared light

FIGURE 7

Figure 7
Sentinel lymph node ex-vivo under white light

FIGURE 8

Figure 8
Sentinel lymph node ex-vivo under near-infrared light