Lung cancer often spreads to the lymph nodes before spreading to other parts of the body. Which groups of lymph nodes are involved, and where these are in relation to the primary (original) tumor, are important factors in determining the stage of cancer and how it should be treated.
If you read the report of a scan or biopsy, you may see the phrase “metastatic to lymph nodes.” Having cancer that has metastasized (spread) to lymph nodes does not mean that you have metastatic cancer. Even some early-stage cancers, like some stage 2A lung cancers, have positive lymph nodes but are in no way metastatic.
With that said, the presence of cancer in lymph nodes tells doctors that the tumor intends to spread and that more aggressive treatment may be needed to reduce the risk of recurrence.
Lymph Node Metastases
Lung cancer can directly invade nearby tissues. It can also spread as cancer cells break off from the primary tumor and are transported through one of three systems:
- The lymphatic system, consisting of lymph fluid, lymphatic vessels, and lymphatic organs like lymph nodes and the spleen
- The circulatory system, consisting of blood and blood vessels
- The bronchial tree, involving the airways of the lungs through which lung cancer is now thought to be able to spread
When cancer cells travel through the lymphatic system, they are carried to lymph nodes which act as filters for body wastes, toxins, and other harmful substances. Lymph nodes are clustered throughout the body, the groupings of which are classified by their location.
Lymph nodes often serve as the “firewalls” for cancer as cells are shed from the primary tumor.
When the spread is limited to nearby (regional) lymph nodes, the cancer can be described as locally advanced.
If the lung cancer has spread beyond regional lymph nodes and is found in distant lymph nodes or other tissues, the disease is considered metastatic.
Regional Lymph Node Classifications
When cancer has spread to regional lymph nodes, they are classified by their location in and around their lungs. The location plays a key role in the staging of lung cancer.
For the purpose of staging, regional lymph nodes are divided into three groups:
- Intrapulmonary lymph nodes: This refers to lymph nodes that lie within the lungs. These can either be peripheral lymph nodes found in the outer regions of the lungs or hilar lymph nodes found where the major airways (bronchi) and major blood vessels enter the lungs (called the hilum).
- Mediastinal lymph nodes: These are lymph nodes situated in the area between the chest wall and the lungs (called the mediastinum). These also include lower mediastinal lymph nodes such as subcarinal lymph nodes surrounding the windpipe (trachea) and peribronchial lymph nodes surrounding the bronchi.
- Extrathoracic lymph nodes: This refers to lymph nodes situated on the outside of the thorax (chest). These include supraclavicular lymph nodes found just above the collarbone (clavicle) and scalene lymph nodes found in the neck near the uppermost rib.
Another way that lymph nodes are classified is by the side of the body where they are located:
- Ipsilateral lymph nodes: Ipsilateral refers to lymph nodes on the same side of the body as the primary tumor.
- Contralateral lymph nodes: Contralateral lymph nodes are on the opposite side of the chest from the tumor.
You will often not have any specific symptoms indicating that has cancer spreads to your lymph nodes. If you do, they may include:
- Swelling in your neck or in the area just above your collarbone
- Shortness of breath due to pressure from swollen lymph nodes in your chest
Beyond that, any symptoms you have may be related to lung cancer in general. Early signs may include:
- Persistent cough with dark or bloody phlegm
- Hoarse voice
- Chest pain
- Frequent respiratory infections
- Fatigue or weakness
- Loss of appetite
- Unintended weight loss
After lung cancer is diagnosed, your physician will order tests to see if your tumor has spread to lymph nodes or distant sites.
Determining which, if any, lymph nodes in your body are affected by cancer is important in selecting the best treatment options for you as an individual. It can be an arduous and stressful process but one that can ensure you are neither undertreated nor overtreated.
Common diagnostic tests include:
- Computed tomography (CT), which uses a series of coordinated X-ray images to create a three-dimensional scan
- Magnetic resonance imaging (MRI), which uses powerful radio and magnetic waves to create high-definition images, especially of soft tissues
- Positron emission tomography (PET), which uses a radioactive tracer to highlight metabolic activity in the lung, helping differentiate between benign masses that aren’t progressing and cancerous ones that are
- Endobronchial ultrasound, which involves the insertion of a flexible ultrasound into the airway to indirectly visualize tissues using sound waves
- Mediastinoscopy, which involves the insertion of a lighted scope (called a mediastinoscope) into the space between the breastbone and lungs to directly visualize tissues
- Lymph node biopsy, in which a sample of tissue is extracted (often during an endobronchial ultrasound or mediastinoscopy) for evaluation in the lab
In the past, mediastinoscopy was the procedure most commonly used to diagnose lung cancer. But, because mediastinoscopy is an invasive surgical procedure, it has been largely replaced by PET scans that are less invasive and nearly as sensitive.
Lymph node involvement is one of the factors used in the staging of cancers, including lung cancer. It is part of a classification system called TNM staging which categorizes cancer by the size of the primary tumor (T), the number and location of regional lymph nodes (N), and the presence or absence of metastasis (M).
Lymph nodes are classified by the numbers 0 to 3 or the letter “x” as follows:
- N0: The tumor has not spread to lymph nodes.
- Nx: It cannot be determined if cancer has spread to the lymph nodes or not.
- N1: The tumor has spread to nearby nodes on the same side of the body.
- N2: The tumor has spread to nodes further away but on the same side of the body.
- N3: Cancer cells have spread to lymph nodes on the opposite side of the chest to the tumor or to lymph nodes near the collarbone or neck muscles.
While each advancing number in the N value describes a progression of the disease, it does not indicate metastasis. Metastasis is only represented in TNM staging by the M values, either with M0 (no metastasis) or M1 (metastasis).
The specific criteria for lymph node classification are described in the 7th edition of Lung Cancer Staging issued by the American Joint Committee on Cancer.
|N Staging||Regional Lymph Node Involvement|
|N0||No lymph node involvement|
|N1||Metastasis in ipsilateral peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary nodes|
|N2||Metastasis in ipsilateral mediastinal and/or subcarinal lymph nodes|
|N3||Metastasis in contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular lymph node(s)|
The treatment for lung cancer that has spread to lymph nodes depends upon the stage of cancer and your general health.
If lung cancer has spread to only a few nearby lymph nodes, surgical treatment may be considered. The procedure, referred to as selective lymph node dissection (SLND), aims to remove affected lymph nodes and preserve those that are free of cancer.
SLND is typically used for N1 disease but can also be used as a preventive measure in people with N0 disease.
Prior to the SLND procedure, a PET scan will be performed with or without an accompanying CT scan with contrast. This helps the surgeon pinpoint which lymph nodes are affected. The surgeon can then decide which to remove based on the pattern of lymph node drainage. To be safe, the surgeon will usually remove several unaffected lymph nodes just beyond the boundary of the affected ones.
SLND typically requires a two- to three-day hospital stay. Bleeding and pain are common after the surgery, but infection is rare.
After the lymph nodes are removed, radiation therapy may be used to kill any remaining cells and prevent a recurrence.
SLND is rarely if ever used when there are numerous affected lymph nodes. In such cases, standard therapies will be pursued.
On their own, the N values in the TNM system only provide a glimpse of the long-term outcomes of cancer. It is only by comparing lymph node involvement with the characteristics of the primary tumor and the presence or absence of metastasis that a doctor can provide you with a reasonable prognosis.
With that said, a 2016 study in the Journal of Thoracic Diseases described certain lymph node characteristics than may indicate better or poorer outcomes:
- The numeric values used in lymph node classification are generally strong indicators of survival times. People with N0 have the most favorable outcomes, while those with N3 have the least favorable outcomes.
- In people with N1 disease, outcomes are better if the affected lymph nodes are in the hilar zone rather than the peripheral zone.
- In people with N2 disease, outcomes are better if only N2 zones are involved but not N1 zones; this is referred to as a “skipped metastases.” The involvement of both N1 and N2 zones generally indicates a poorer outcome.
In the end, the best way to predict long-term outcomes in people with lung cancer is by factoring in all three values of the TNM system. This can vary by whether you have small-cell lung cancer (SCLC) or non-small-cell lung cancer (NSCLC).
Five-year survival is a standardized measure used by doctors to predict how many people are likely to survive at least five years following the cancer diagnosis. This is broken down by whether the disease is localized (confined to one lung), regional (involving regional lymph nodes or nearby tissues), or distant (metastatic).
The five-year survival rate for lung cancer is broadly defined by the National Cancer Institute (NCI) as follows:
All stages: 6%
All stages: 23%
A Word From Get Meds Info
It is important to become part of this process as a partner in your own care. If there is something you don’t understand, let the doctor know. By understanding as much you can about your diagnosis and treatment, you can make more informed choices and feel more in control of your condition.
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