What are the most common sentinel lymph nodes for lung cancer?

From the Guidelines

The most common sentinel lymph nodes for lung cancer are the hilar and mediastinal lymph nodes, as indicated by the N descriptor in the eighth edition of the lung cancer staging guidelines 1. These nodes are typically the first to receive lymphatic drainage from the lungs and are therefore the initial sites where cancer cells spread via the lymphatic system. The specific pattern of lymphatic spread depends on the tumor's location within the lung. For right lung tumors, lymphatic drainage commonly involves the right paratracheal, subcarinal, and hilar lymph nodes. Left lung tumors typically drain to the left hilar, subcarinal, and aortopulmonary window lymph nodes. Upper lobe tumors tend to spread to superior mediastinal nodes, while lower lobe tumors often drain to inferior mediastinal and subcarinal nodes. Identifying these sentinel nodes is crucial for accurate staging of lung cancer, which directly impacts treatment decisions and prognosis. During surgical resection or biopsy procedures, surgeons systematically examine these lymph node stations to determine the extent of disease spread. The presence of metastatic disease in these nodes significantly alters the cancer stage and may necessitate more aggressive treatment approaches including adjuvant chemotherapy or radiation therapy. Some key points to consider when evaluating the sentinel lymph nodes for lung cancer include:

• N1 includes ipsilateral peribronchial, hilar, or intra-pulmonary lymph node(s) 1
• N2 describes ipsilateral mediastinal or subcarinal lymph node(s) 1
• N3 includes contralateral mediastinal or hilar lymph node(s) and any supraclavicular or scalene node on either side 1
• A lymph node size threshold of >10 mm in axial short axis diameter is considered abnormal 1
• The prevalence of metastatic lung cancer in thoracic lymph nodes is 30% for nodes that are 10 to 15 mm in short axis diameter and 67% for nodes >15 mm 1

From the Research

Sentinel Lymph Nodes in Lung Cancer

The location of sentinel lymph nodes (SLNs) in lung cancer patients can vary depending on the affected lobe and tumor characteristics.

• The most common locations for SLNs are:
  • Hilar area: This is the most common location for SLNs, especially for tumors located in the right upper lobe, right middle lobe, and right lower lobe 2, 3, 4.
  • Mediastinal stations: SLNs can also be found in mediastinal stations, particularly for tumors located in the left upper lobe and left lower lobe 2, 3, 5.
• Tumor characteristics, such as size and histological type, do not seem to affect the distribution of SLNs 2.
• The identification of SLNs can be useful for minimizing lymph node dissection and targeting the best lymph nodes for intraoperative frozen section during segmentectomy 6.

Location of Sentinel Lymph Nodes by Lobe

The location of SLNs can vary depending on the affected lobe:

• Right upper lobe: SLNs are often found in the hilar area, specifically in stations #3 and #4 5.
• Right middle lobe: SLNs are often found in the hilar area, specifically in stations #3 and #7 5.
• Right lower lobe: SLNs are often found in the hilar area, specifically in station #7 5.
• Left upper lobe: SLNs are often found in the mediastinal stations, specifically in stations #5 and #6 5.
• Left lower lobe: SLNs are often found in the mediastinal stations, specifically in station #7 5.

Identification of Sentinel Lymph Nodes

SLNs can be identified using various methods, including:

• Radioisotope tracing: This involves injecting a radioactive tracer into the tumor and then using a gamma counter to detect the SLNs 6, 3, 4.
• In vivo counting: This involves using a gamma counter to detect the SLNs during surgery 3.
• Ex vivo counting: This involves removing the lymph nodes and then using a gamma counter to detect the SLNs 3.