Guiding the Way: Sentinel Lymph Node Mapping With ICG in Sublobar Resections

Sentinel lymph node (SLN) biopsy is the standard of care in multiple fields of surgery; however, its clinical use in thoracic surgery remains limited. Given the extremely variable lymphatic drainage in the chest and the prevalence of skip metastases, SLN mapping can better identify lymph nodes with occult disease. The rationale behind SLN mapping lies in its role as the first site of metastatic spread, making it a crucial indicator for broader nodal involvement. This is paramount given that the consequences of potential under-staging include the risk of local recurrence. As the first site of nodal disease, intraoperative assessment of the SLN could confirm N0 status and candidacy for sublobar resection. 
 
Widespread adoption of SLN mapping in thoracic surgery is possible with the development of safe, reliable, and cost-effective methods for SLN identification. Indocyanine green (ICG) allows for real-time visualization of anatomic structures, surgical planes, tumor, and lymphatic channels. Its low toxicity, low cost, and low allergy index make it a promising agent as a fluorescent dye in SLN mapping. In this video, the authors describe their technique for SLN mapping in a robotic-assisted sublobar resection. 
 
The patient was a 77-year-old female with a growing, peripherally located 2 cm FDG-avid nodule. A percutaneous biopsy at an outside hospital confirmed malignancy, prompting her consultation with thoracic surgery. She consented to undergo robotic-assisted SLN mapping with resection of the lingula and potential left upper lobectomy. 
 
In the operating room, the mass in the left upper lobe was identified, and 0.5 cc of ICG at a concentration of 2.5 mg/cc was injected peritumorally. Contrary to expectations, the lymphatic channel did not map to the adjacent hilar lymph nodes, but rather to a subaortic level 5 lymph node. Frozen section pathology of the SLN revealed no malignancy, allowing the surgery to conclude with an anatomic segmentectomy of the lingula. 
 
Her final pathology was consistent with a typical carcinoid tumor, with no evidence of disease in any of the resected lymph nodes. At six months postoperation. The patient  continues to follow-up with medical oncology, with no evidence of disease. In an era where more sublobar resections are being performed, SLN mapping with ICG allows for accurate staging and confirmation of N0 status prior to proceeding with anatomic segmentectomy. 

References

1. Phillips WW, Weiss KD, Digesu CS, Gill RR, Mazzola E, Tsukada H, Schumacher LY, Colson YL. Finding the "True" N0 Cohort: Technical Aspects of Near-infrared Sentinel Lymph Node Mapping in Non-small Cell Lung Cancer. Ann Surg. 2020 Oct;272(4):583-588. doi: 10.1097/SLA.0000000000004176. PMID: 32657925.

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