Squamous cell lung cancer is a subtype of non-small cell lung cancer (NSCLC), which accounts for about 85% of all lung cancers. This cancer originates in the squamous cells, which are thin, flat cells that line the airways. The tumors most often develop in the central part of the lungs or near the main airways, known as the bronchi.
Under a microscope, these cancerous cells have distinct features. Squamous cell carcinoma constitutes roughly 30% of all NSCLC diagnoses, making it a common form of lung cancer. Its development is closely linked to a history of smoking and it tends to be found near a main airway.
Causes and Symptoms
The primary cause of squamous cell lung cancer is cigarette smoking, linked to approximately 80% of cases in men and 90% in women. The carcinogens in tobacco smoke damage the squamous cells lining the airways, leading to malignant transformations. Other risk factors include exposure to secondhand smoke, radon gas, asbestos, and other environmental pollutants. A family history of lung cancer also increases an individual’s risk.
Symptoms often do not appear in the early stages. As a tumor grows, it may cause a persistent cough, chest pain that worsens with deep breathing, and shortness of breath. Individuals may experience wheezing, hoarseness, or recurrent lung infections like bronchitis and pneumonia. Coughing up blood or reddish phlegm is a notable symptom, appearing earlier in squamous cell carcinoma than in other lung cancer types because of the tumors’ location near central airways.
Diagnosis and Staging
Confirming a diagnosis involves a multi-step process that begins with imaging tests. A chest X-ray is often the first step, but a computed tomography (CT) scan provides more detailed pictures of the lungs and can identify suspicious masses. A classic sign of squamous cell carcinoma on a CT scan can be the presence of a cavity within a tumor mass.
While imaging can detect a potential tumor, a definitive diagnosis requires a biopsy. A small tissue sample is removed from the suspicious area for examination by a pathologist. This can be done through various methods, such as a bronchoscopy, where a thin tube is passed down the throat to the airways, or a needle biopsy, where a needle is guided through the chest wall into the lung tumor.
Once cancer is confirmed, staging is performed to determine the extent of its spread. The common TNM system assesses the tumor’s size and location (T), its spread to nearby lymph nodes (N), and whether it has metastasized to distant parts of the body (M). This information is combined to assign a stage, from Stage I (localized cancer) to Stage IV (cancer that has spread distantly). Staging is important for determining the most appropriate treatment plan and helping to predict a patient’s prognosis.
Treatment Approaches
The treatment for squamous cell lung cancer is dependent on the stage of the disease at diagnosis. The patient’s overall health and lung function are also important considerations. A team of specialists collaborates to create a plan that may involve one or more treatment types.
For early-stage, localized tumors (Stage I and II), surgery is the primary treatment. A surgeon may perform a lobectomy, removing the entire lobe of the lung where the tumor is located, or a more limited resection for smaller tumors. Chemotherapy may be recommended to eliminate any remaining cancer cells and reduce the risk of recurrence.
Radiation therapy uses high-energy rays to kill cancer cells. It can be the main treatment for patients who are not healthy enough for surgery, or it can be used after surgery to target any cancer cells left behind. For more advanced cancers (Stage III), radiation is often combined with chemotherapy, a treatment known as chemoradiation.
In advanced or metastatic squamous cell lung cancer (Stage IV), systemic therapies that travel through the bloodstream are the mainstays of treatment. Chemotherapy is a standard approach. Targeted therapy drugs work by attacking specific abnormalities within cancer cells, though targetable mutations are less common in squamous cell cancer than in other NSCLC subtypes. An advancement has been the development of immunotherapy, which helps the body’s own immune system recognize and fight cancer cells. Drugs known as checkpoint inhibitors have become a standard part of treatment for many patients with advanced disease.
Prognosis and Survival Rates
The prognosis for squamous cell lung cancer is influenced by the stage at diagnosis, a patient’s overall health, and their response to treatment. Survival rates are discussed in terms of 5-year relative survival, which compares people with the same type and stage of cancer to the general population. These are statistical averages and cannot predict an individual’s outcome.
When the cancer is localized, meaning it has not spread outside the lung, the 5-year survival rate is higher. For non-small cell lung cancer, which includes squamous cell carcinoma, the 5-year survival rate for localized disease can be over 60%. If the cancer has spread to nearby lymph nodes (regional spread), the rate is lower, around 40%.
For distant-stage cancer, where it has metastasized to other parts of the body, the prognosis is more challenging. The 5-year survival rate for stage IV non-small cell lung cancer is approximately 5-7%. However, ongoing advancements in treatments, particularly immunotherapy and targeted therapies, are leading to improvements in survival for patients even with advanced disease.