Introduction: Who Should Undergo Diagnostics and When

If you notice any unusual changes on your skin that do not go away, it is important to seek medical attention. Metastatic skin squamous cell carcinoma, often called cSCC (cutaneous squamous cell carcinoma), can develop when cancer that started in the skin spreads to other areas of your body. This is a more serious situation than early-stage skin cancer, and catching it quickly can affect your treatment options and outcomes.^[2]

Anyone who has already been treated for squamous cell carcinoma on the skin should be especially vigilant. Metastasis, which means the cancer has traveled to other parts of the body, happens in a small percentage of cases. Research shows that metastasis occurs in about three to nine percent of cutaneous squamous cell carcinoma cases, typically within one to two years after the initial diagnosis.^[2] This means that even after successful treatment of a skin lesion, regular follow-up and monitoring are essential to catch any spread early.

You should consider seeking diagnostics if you notice a lump or mass in your neck or around your collarbone that does not go away. A persistent lump or pain in the neck or throat can be a warning sign that squamous cell cancer has spread to the lymph nodes, which are small bean-shaped structures that help fight infections.^[12] Sometimes, doctors find cancer in the lymph nodes of the neck even when they cannot immediately identify where the cancer originally started. This situation is called metastatic squamous neck cancer with occult (hidden) primary.^[12]

People who have certain risk factors for aggressive disease should be more proactive about diagnostics. If you have a weakened immune system, have received an organ transplant, or have had repeated treatments for a skin lesion that keeps coming back, these factors increase the chance that your cancer could spread.^[3][11] In such cases, your doctor may recommend more frequent examinations and diagnostic tests to monitor for any signs of metastasis.

Diagnostic Methods: Identifying the Disease and Distinguishing It From Other Conditions

The process of diagnosing metastatic squamous cell carcinoma begins with a thorough physical examination. Your doctor will ask about your personal health history, including any past skin cancers, sun exposure, and symptoms you have noticed. They will carefully examine your skin, looking for any abnormal bumps, growths, sores, or changes in texture and color.^[8][14] This visual inspection is often the first step in identifying whether a suspicious area might be cancerous.

When a concerning area is found, a biopsy is the next critical step. A biopsy involves removing a sample of tissue from the suspicious area so it can be examined under a microscope in a laboratory. There are different ways to perform a biopsy. Your doctor might use a tool to cut away, shave off, or punch out some or all of the abnormal skin area.^[8][14] The tissue sample is then analyzed to determine whether cancer cells are present and, if so, what type of cancer it is. This test confirms whether you have squamous cell carcinoma and provides information about the characteristics of the cancer cells.

If the biopsy confirms squamous cell carcinoma, additional tests may be needed to determine whether the cancer has spread beyond the original skin site. This is especially important when the cancer has certain high-risk features such as large size, deep invasion into the skin layers, or location in areas like the ears or lips.^[2][4] Understanding the extent of the disease helps doctors plan the most appropriate treatment approach.

When doctors suspect that squamous cell carcinoma has spread to other parts of the body, they may use imaging tests to get a clearer picture of what is happening inside. Computed tomography (CT) scans use X-rays and computer technology to create detailed, three-dimensional images of the body. These scans can help identify whether cancer has spread to lymph nodes, bones, or internal organs.^[3] CT scans are particularly useful for examining the chest, abdomen, and other areas where metastasis might occur.

Another imaging technique that may be used is ultrasound. Ultrasound uses sound waves to create real-time pictures of the inside of the body. It can be helpful in examining lumps or masses in the neck and determining whether lymph nodes are enlarged or abnormal.^[3] This non-invasive test is often used when doctors want to assess the lymph nodes without immediately resorting to surgery.

In some cases, doctors may recommend a positron emission tomography (PET) scan. A PET scan uses a small amount of radioactive material to highlight areas of the body where cells are more active, which can indicate the presence of cancer. This test can help detect metastatic cancer in various parts of the body and is particularly useful when doctors need to determine the full extent of the disease.^[3]

When cancer is found in the lymph nodes of the neck but the original tumor location is not obvious, additional diagnostic procedures are performed to search for the primary tumor. This is important because treatment for metastatic cancer is typically based on where the cancer first started. Doctors may perform a detailed examination of the respiratory tract (including the trachea and lungs), the upper digestive tract (including the mouth, tongue, throat, and esophagus), and other areas where squamous cells are found.^[12]

To examine these areas, doctors may use procedures such as endoscopy. During an endoscopy, a thin, flexible tube with a camera on the end is inserted through the mouth or another opening to allow doctors to see inside the body. For example, a bronchoscopy examines the airways and lungs, while an upper endoscopy looks at the esophagus and stomach. These procedures can help identify a hidden primary tumor that might be the source of the metastatic cancer.^[12]

Sometimes, despite thorough investigation, doctors cannot find where the cancer originally started. In these cases, the primary tumor is called occult, meaning it remains hidden. Even when the primary tumor is not found, doctors can still make a diagnosis of metastatic squamous neck cancer based on the characteristics of the cancer cells found in the lymph nodes.^[12] The cancer cells in metastatic sites retain features of squamous cells, which helps doctors identify the type of cancer even without locating the original tumor.

Laboratory tests on tissue samples can provide important information about the cancer. Pathologists, who are doctors specializing in examining tissues and cells, analyze the biopsy samples to determine the type of cancer, how aggressive it appears, and whether it has certain characteristics that might affect treatment decisions. For example, they may look at how deeply the cancer has invaded the skin layers and whether it involves nerves or blood vessels, which are factors that increase the risk of metastasis.^[2]

Diagnostics for Clinical Trial Qualification: Tests Used as Entry Criteria

When patients with advanced or metastatic squamous cell carcinoma consider participating in clinical trials, specific diagnostic tests are often required to determine whether they qualify for enrollment. Clinical trials are research studies that test new treatments or combinations of treatments to find better ways to manage cancer. These studies have strict eligibility criteria to ensure that participants are appropriate candidates and that the results of the trial will be meaningful.

Before enrolling in a clinical trial, comprehensive diagnostic testing is typically performed to establish a baseline understanding of your disease. This includes confirming the diagnosis of metastatic squamous cell carcinoma through biopsy and tissue analysis. The tissue samples may undergo additional laboratory testing to identify specific characteristics of the cancer cells, such as genetic mutations or the presence of certain proteins on the cell surface.^[4][10]

One important aspect of diagnostic evaluation for clinical trial entry is staging the cancer. Staging describes how much cancer is in the body and where it is located. It helps doctors understand how advanced the disease is and predict how it might behave. For squamous cell carcinoma, staging considers factors such as the size of the primary tumor, how deeply it has grown into the skin and underlying tissues, whether it has spread to nearby lymph nodes, and whether it has metastasized to distant organs.^[10][17]

To accurately stage the cancer, imaging tests such as CT scans, PET scans, and sometimes MRI (magnetic resonance imaging) scans are performed. These tests create detailed pictures of the inside of your body and help identify all areas where cancer is present. Accurate staging is crucial for clinical trials because many studies are designed for specific stages of disease. For example, some trials may only accept patients with locally advanced disease that cannot be removed by surgery, while others may focus on patients with distant metastasis.^[4][6]

In addition to imaging, blood tests may be part of the diagnostic workup for clinical trial qualification. Blood tests can assess your overall health and organ function, which is important because some treatments being studied in clinical trials can affect the kidneys, liver, or other organs. Tests may include a complete blood count to check the levels of different blood cells, tests to evaluate kidney and liver function, and measurements of electrolytes and other substances in the blood.^[3]

Some clinical trials are testing treatments that target specific molecular features of cancer cells. For these trials, additional diagnostic tests called biomarker testing or molecular profiling may be required. Biomarkers are substances found in cancer cells that can indicate how the cancer might respond to certain treatments. For example, some studies examine whether the cancer cells express a protein called epidermal growth factor receptor (EGFR), which can influence treatment decisions.^[7] Tissue samples from your biopsy may be sent to specialized laboratories for these tests.

Clinical trials may also require documentation of previous treatments you have received. This includes records of any surgeries, radiation therapy, or systemic treatments such as chemotherapy. Understanding your treatment history helps researchers determine whether you meet the eligibility criteria and whether the trial’s intervention is appropriate for your situation.^[10][17]

Another common requirement for clinical trial enrollment is confirmation that the cancer is truly metastatic or locally advanced and not amenable to standard curative treatments. This means that surgery or radiation therapy alone would not be sufficient to control the disease. Doctors use a combination of imaging findings, physical examination, and pathology results to make this determination.^[4][6] Advanced squamous cell carcinomas are defined as those that are large, have penetrated deep into underlying tissues, have spread to lymph nodes or distant sites, or have recurred despite previous treatments.

Performance status assessment is another diagnostic consideration for clinical trials. Performance status measures how well you can carry out daily activities and is used to assess your overall health and ability to tolerate treatment. Doctors may use standardized scales to evaluate your performance status as part of the eligibility screening for a clinical trial.^[5] This assessment helps ensure that you are healthy enough to participate in the study and that the treatment being tested is appropriate for your condition.