Introduction: When to Seek Diagnostic Testing

If you experience certain warning signs, it may be time to talk to your doctor about lung cancer testing. Metastatic lung squamous cell carcinoma is a type of non-small cell lung cancer that has spread from the lung to other parts of the body, and early detection can make a significant difference in treatment options.^[1]

You should consider seeking diagnostic testing if you notice persistent symptoms such as a cough that won’t go away, chest pain that doesn’t improve, shortness of breath, or coughing up blood. Other concerning signs include wheezing, hoarseness in your voice, recurring chest infections like bronchitis or pneumonia, unexplained weight loss, loss of appetite, and ongoing fatigue. Many people with squamous cell carcinoma may not experience symptoms in the early stages, but as the disease progresses, these symptoms can become more noticeable. Because squamous cell carcinoma often starts in the central part of the lung near the main airways, it may cause symptoms like coughing up blood at an earlier stage compared to other types of lung cancer.^[1][4]

People who have a history of smoking or are current smokers should be especially vigilant, as approximately 80% of lung squamous cell carcinoma cases in men and 90% of cases in women are associated with smoking. This type of lung cancer is more strongly linked to smoking than any other form of non-small cell lung cancer. Even if you have quit smoking, your risk remains elevated, particularly if you smoked heavily for many years. Other risk factors that should prompt you to discuss screening with your doctor include exposure to secondhand smoke, occupational exposure to asbestos, arsenic, chromium, or other cancer-causing substances, and a family history of lung cancer.^[1][6]

Classic Diagnostic Methods

When your doctor suspects lung squamous cell carcinoma, several diagnostic tests are typically performed to confirm the presence of cancer, determine its type, and understand how far it has spread. The diagnostic process usually begins with imaging studies and progresses to more specific tests as needed.^[1]

Imaging Tests

The first step in diagnosing lung cancer is often a chest X-ray, which can reveal abnormal masses or areas in your lungs. However, X-rays provide limited detail, so if something suspicious is found, your doctor will typically order more advanced imaging. A computed tomography scan, also known as a CT scan, is frequently the next step. CT scans use X-rays taken from different angles to create detailed, three-dimensional images of your lungs. These scans can show the size and location of tumors, whether lymph nodes are enlarged, and if cancer has spread to nearby structures. CT imaging is often the initial method used to evaluate squamous cell carcinoma, as long as the tumor is large enough to be detected.^[1][20]

Additional imaging tests may be ordered to determine if the cancer has spread to other parts of your body. A positron emission tomography scan, or PET scan, uses a small amount of radioactive sugar to identify areas where cancer cells are actively growing. Cancer cells absorb more of this sugar than normal cells, making them appear as bright spots on the scan. PET scans are particularly useful for detecting cancer that has spread to lymph nodes or distant organs. Magnetic resonance imaging, or MRI, may be used to get detailed images of the brain or other soft tissues if doctors suspect the cancer has spread there. Bone scans can help identify whether cancer has reached the bones.^[5][20]

Laboratory Tests and Sputum Analysis

Blood tests alone cannot diagnose lung cancer, but they provide important information about your overall health and how well your organs are functioning. These tests can help your medical team understand whether you’re strong enough for certain treatments. In some cases, doctors may examine your sputum—the mucus you cough up from your lungs. Under a microscope, sputum can sometimes reveal cancer cells, though this test is not always conclusive. If you’re coughing up sputum, your doctor may collect samples over several days to look for abnormal cells.^[5]

Biopsy Procedures

While imaging tests can suggest the presence of cancer, a biopsy—removing a small sample of tissue for laboratory examination—is the only way to definitively confirm a diagnosis of squamous cell carcinoma. There are several ways to obtain tissue samples from the lung, and your doctor will choose the method based on the tumor’s location and your overall health.^[20]

A bronchoscopy is a common procedure used when the tumor is located in or near the major airways. During this test, a thin, flexible tube with a light and camera on the end is inserted through your mouth or nose and guided down into your lungs. The doctor can see inside your airways and use small instruments passed through the tube to collect tissue samples. This procedure is typically done under sedation to keep you comfortable. Bronchoscopy is particularly useful for squamous cell carcinomas, which often develop in the central airways near the main bronchi.^[1][20]

For tumors located in the outer areas of the lung that can’t be reached by bronchoscopy, doctors may perform a needle biopsy. In this procedure, a thin needle is inserted through your chest wall and into the lung tumor, usually guided by CT imaging to ensure accurate placement. The needle collects a small sample of tissue, which is then examined under a microscope. Though this might sound uncomfortable, the area is numbed beforehand, and most people tolerate the procedure well.^[20]

In certain situations, more invasive surgical procedures may be necessary to obtain tissue samples. A mediastinoscopy involves making a small incision at the base of your neck and inserting a thin tube to examine and sample lymph nodes in the area between your lungs. This helps determine if cancer has spread to nearby lymph nodes. Thoracentesis, also called pleural fluid sampling, may be performed if fluid has accumulated around your lungs. A needle is inserted between your ribs to remove fluid, which is then checked for cancer cells.^[5]

Pathological Examination and Classification

Once tissue samples are obtained, they are examined by a pathologist—a doctor who specializes in diagnosing diseases by looking at cells and tissues under a microscope. The pathologist can identify whether the cancer is squamous cell carcinoma by looking at the cell structure and characteristics. Squamous cells are flat cells that line the airways, and when they become cancerous, they have distinct features that can be recognized under microscopic examination. The World Health Organization recognizes three subtypes of squamous cell lung carcinoma based on how the cells appear: keratinizing, nonkeratinizing, and basaloid squamous cell carcinoma.^[1][8]

In addition to confirming the cancer type, the pathologist will also conduct special tests called immunohistochemistry, which use antibodies to detect specific proteins in the cancer cells. These tests help distinguish squamous cell carcinoma from other types of lung cancer and can provide information about the cancer’s behavior. Understanding the exact type of cancer is crucial because different types respond differently to various treatments.^[1]

Staging the Cancer

After diagnosing squamous cell carcinoma, doctors need to determine the cancer’s stage—how large the tumor is and how far it has spread. Metastatic lung squamous cell carcinoma means the cancer has spread beyond the lungs to other parts of the body. This is classified as stage 4, the most advanced stage of lung cancer. Stage 4 is further divided into stage 4A and stage 4B based on how widely the cancer has spread.^[4][8]

In stage 4A, the cancer may have spread to the other lung, the fluid around the lung or heart, or to one distant area outside the chest. In stage 4B, cancer has spread to multiple locations far from the original tumor, which might include the liver, bones, brain, adrenal glands, or multiple sites. The staging process uses information from all the diagnostic tests—imaging studies, biopsies, and laboratory results—to create a complete picture of the cancer’s extent. This information is essential for planning treatment, as different stages require different approaches.^[5][8]

Diagnostics for Clinical Trial Qualification

If you’re considering participating in a clinical trial for metastatic squamous cell lung cancer, you’ll likely need to undergo additional diagnostic testing. Clinical trials are research studies that test new treatments or combinations of treatments, and they have specific requirements about who can participate. These requirements, called eligibility criteria, help ensure that the study results are reliable and that participants are likely to benefit from the experimental treatment.^[1]

Biomarker Testing

One of the most important tests for clinical trial qualification is biomarker testing, which looks for specific genetic changes or proteins in your cancer cells. While squamous cell lung cancer has fewer targetable genetic mutations compared to other types of lung cancer like adenocarcinoma, testing is still important. Some clinical trials specifically look for patients whose cancers have certain characteristics or lack certain mutations. The tissue samples collected during your biopsy will be analyzed for various genetic markers, which can help match you to appropriate clinical trials and treatment options.^[1]

PD-L1 Testing

Many modern clinical trials for metastatic lung cancer focus on immunotherapy drugs, which help your immune system fight cancer. To determine if you might respond to these treatments, doctors test for a protein called PD-L1 on the surface of cancer cells. PD-L1 testing is performed on the biopsy tissue using immunohistochemistry. The test measures what percentage of cancer cells express this protein. Some clinical trials accept patients with any PD-L1 level, while others specifically look for high levels (such as 50% or greater) or low levels. Your PD-L1 level can influence which clinical trials you might be eligible for and which treatments your doctor might recommend.^[13]

Performance Status Assessment

Clinical trials typically require an assessment of your overall functional ability, often called your performance status. This isn’t a laboratory test but rather an evaluation of how well you can carry out daily activities. Doctors use standardized scales to rate your ability to care for yourself, work, and stay active. Your performance status helps researchers understand how healthy you are overall, beyond just the cancer itself. Most clinical trials only accept patients who are relatively strong and active, as they’re more likely to tolerate the experimental treatments and complete the study. If you’re interested in a clinical trial, your doctor will evaluate your performance status as part of determining your eligibility.^[1]

Organ Function Tests

Before enrolling in a clinical trial, you’ll typically need blood tests to check how well your organs are functioning. These tests measure your blood cell counts, kidney function, and liver function. Clinical trials have specific thresholds for these values to ensure that participants are healthy enough to handle the experimental treatment. For example, your kidneys need to work well enough to process medications, and your liver needs to be able to break down drugs. Your blood counts must be adequate to support your immune system and carry oxygen throughout your body. These organ function tests may need to be repeated periodically during the trial to monitor your health.^[12]

Documentation of Metastatic Disease

For clinical trials specifically designed for metastatic squamous cell carcinoma, clear documentation that the cancer has spread beyond the lungs is required. This documentation comes from imaging studies like CT scans, PET scans, or MRI scans that show cancer in distant organs or tissues. The research team will review all your imaging results to confirm that you meet the trial’s definition of metastatic disease. In some cases, biopsies of metastatic sites may also be required to prove that the distant tumors are indeed lung cancer that has spread, rather than a separate new cancer.^[7]

Previous Treatment History

The clinical trial team will need detailed records of any previous cancer treatments you’ve received. Some trials are designed for patients who have never been treated before (first-line treatment trials), while others are specifically for patients whose cancer has progressed after one or more previous treatments. You’ll need to provide documentation of previous chemotherapy regimens, radiation therapy, immunotherapy, or other treatments, including the dates, doses, and your response to those treatments. This information helps researchers determine if you’re appropriate for their study and helps them interpret the results of the trial.^[13]