Lung cancer is a disease that begins in the cells of the lungs. Like other types of cancer, it occurs when cells grow and divide uncontrollably, forming tumors and potentially spreading to other parts of the body.

Each type of cancer is named based on the cells where it originates. Lung cancer starts specifically in the cells of the lung. It’s important to note that cancer from another part of the body that spreads to the lungs is not considered lung cancer. For example, liver cancer that spreads to the lungs is still classified as liver cancer.

The lungs are the primary organs of the respiratory system. Their main job is to exchange gases — bringing oxygen into the body and removing carbon dioxide. Every cell in the body needs oxygen to function, and the lungs are responsible for supplying this oxygen by transferring it from inhaled air into the bloodstream. At the same time, they remove carbon dioxide, a waste product created by cells, from the blood and release it through exhalation.

When you breathe in, air travels through the throat into the windpipe (trachea), which then splits into two tubes called bronchi — one for each lung. The bronchi branch into smaller tubes called bronchioles, which end in tiny air sacs known as alveoli. These alveoli are surrounded by blood vessels, and it’s here that the actual exchange of oxygen and carbon dioxide takes place.

The right lung has three sections, called lobes, while the left lung has two lobes. Each lobe receives air from a branch of the bronchial tree.

The lungs are protected by a thin lining called the pleura, which has two layers:

  • The parietal pleura (outer layer)

  • The visceral pleura (inner layer that covers the lungs)

Between these two layers is the pleural cavity, which contains a small amount of fluid to help the lungs move smoothly during breathing. In cases of lung cancer, cancer cells may sometimes be found in the pleural fluid.

Throughout the lungs and the rest of the body, a clear fluid called lymph flows through vessels and lymph nodes. Lymph helps nourish cells and supports the immune system in fighting infections. In the lungs, lymph nodes are found along the bronchi and are connected to other nodes near the trachea and in the neck. These lymph nodes can also be affected by cancer, either as a site where it begins or spreads.

The symptoms of lung cancer can arise from several different causes:

  1. The tumor itself

  2. Its growth and spread within the chest

  3. Metastatic spread to other parts of the body

  4. Systemic effects not directly caused by the tumor (paraneoplastic syndromes) — These can affect various parts of the body and may include symptoms like fever or other unexpected changes in body function.

Common Symptoms

The most frequent symptom of lung cancer is a persistent cough. Other common signs include:

  • Shortness of breath (dyspnea)

  • Coughing up blood (hemoptysis)

  • Chest pain

  • Fatigue

  • Unexplained weight loss

  • Fever

Symptoms Caused by Tumor Invasion

When the tumor affects nearby tissues or structures, it may lead to:

  • Swollen lymph nodes, especially noticeable in areas like the neck

  • Shoulder or arm pain, or chest pain, often due to nerve involvement

  • Hoarseness or difficulty speaking (dysphonia), which can result from paralysis of a vocal cord

  • Difficulty swallowing, if the tumor presses on the esophagus

Symptoms from Metastasis

If lung cancer spreads to other parts of the body, symptoms will depend on the affected area. For instance:

  • Neurological symptoms if it spreads to the brain

  • Bone pain or fractures if it spreads to the bones

Silent Cases

Sometimes, lung cancer doesn’t cause any symptoms at all and is discovered incidentally. A lung nodule may be found during a routine chest X-ray or CT scan done for another reason. In such cases, further testing is necessary to determine whether the nodule is cancerous.

1. Smoking

Smoking tobacco is the leading risk factor for lung cancer. The more a person smokes and the longer they smoke, the higher their risk of developing the disease.

  • Quitting smoking reduces the risk over time, but former smokers still have a higher risk than those who have never smoked.

  • Second-hand smoke (inhaling smoke from others) also increases the risk of lung cancer, even in non-smokers.

2. Radon and Uranium Exposure

Uranium, a naturally occurring substance found in rocks and soil, can cause lung cancer — especially in uranium miners.
As uranium breaks down, it releases radon gas, which can seep into the air and water.

  • Radon can accumulate indoors, especially in poorly ventilated buildings and basements.

  • The risk of lung cancer increases with higher radon levels and longer exposure.

3. Exposure to Harmful Substances

Long-term exposure to certain chemicals and substances can also raise the risk of lung cancer. These include:

  • Asbestos

  • Arsenic

  • Beryllium

  • Cadmium

  • Chromium

  • Nickel

  • Silica

  • Diesel exhaust

  • Coal smoke and soot

4. Pre-existing Lung Conditions

Certain lung diseases are associated with an increased risk of lung cancer:

  • Chronic Obstructive Pulmonary Disease (COPD)

  • Pulmonary fibrosis (a condition causing scarring of the lung tissue)

5. Family History

People with a family history of lung cancer, especially when multiple relatives have been affected, may be at increased risk — particularly if they also smoke.

6. Other Cancers

Individuals who have had cancers related to smoking may also have a higher risk of developing lung cancer. These include:

  • Stomach cancer

  • Bladder cancer

  • Kidney cancer

  • Pancreatic cancer

  • Cervical cancer

  • Head and neck cancers

  • Acute myeloid leukemia

  • Additionally, people who have had lymphoma may be at increased risk.

Nearly all lung cancers are carcinomas, meaning they originate from epithelial cells—the cells lining the surface of the airways.

Lung carcinomas are divided into two main categories, based on how the cancer cells appear under a microscope:

  1. Non-Small Cell Lung Cancer (NSCLC)

    • The most common type, accounting for about 85% of all lung cancers

    • Includes subtypes such as:

      • Adenocarcinoma

      • Squamous cell carcinoma

      • Large cell carcinoma

  2. Small Cell Lung Cancer (SCLC)

    • Less common but more aggressive

    • Tends to grow and spread faster than NSCLC

Identifying the type of lung cancer is crucial because NSCLC and SCLC differ in their clinical behavior and treatment approaches.

Cancer Staging

Staging describes how far the cancer has spread in the body and is essential for planning treatment.

Doctors usually diagnose and stage lung cancer at the same time using imaging tests, biopsies, and other diagnostic procedures.

The TNM Staging System (by the American Joint Committee on Cancer – AJCC)

  • T (Tumor): Size and location of the primary tumor

  • N (Nodes): Spread to nearby lymph nodes

  • M (Metastasis): Spread to distant parts of the body

The combination of T, N, and M scores determines the overall stage, ranging from 0 to IV:

  • Occult Carcinoma: Cancer cells found in lung fluids or mucus, but no tumor is visible

  • Stage 0 (In situ): Cancer cells are present in the airway lining but haven’t invaded deeper tissues

  • Stages I–III: Cancer has invaded lung tissue and may have spread to nearby lymph nodes

  • Stage IV: The cancer has spread (metastasized) to distant organs or tissues

Prevalence of Lung Cancer

  • Lung cancer is one of the most commonly diagnosed cancers worldwide (excluding certain types of skin cancer).

  • It is also the leading cause of cancer-related deaths globally.

  • It accounts for about 17% of all cancers in men and 9% in women.

Trends vary by country:

  • Higher-income countries often have higher incidence and mortality rates.

  • In some places, rates are declining in men but increasing in women, largely due to historical patterns of smoking.

Prognosis (Outlook)

Several factors influence a person’s prognosis with lung cancer, including:

  • Age and sex

  • Overall lung function

  • Other existing health conditions

  • Type and subtype of cancer (histopathology)

  • Stage at diagnosis (localized, regional, or distant spread)

  • Type of treatment received

By Stage:

  • Localized lung cancer (no spread beyond the lung) has the best prognosis

    • 5-year survival rate: About 58.2%

  • Regional lung cancer (spread to nearby lymph nodes) has a moderate prognosis

  • Distant (metastatic) lung cancer (spread to other organs like brain, liver, or bones) has the lowest survival rates

By Type:

  • NSCLC generally has a better prognosis than SCLC, which progresses more rapidly and is more likely to be diagnosed at an advanced stage.

🩺 Diagnosis of Lung Cancer

To diagnose lung cancer and understand how far it has spread, doctors use several types of tests. These include:

1️⃣ Medical History & Lifestyle Assessment

The first step in diagnosis is a detailed conversation with your doctor. They’ll ask about:

  • Current symptoms: cough, chest pain, shortness of breath, weight loss, etc.

  • Past health problems or treatments

  • Family history of cancer, especially among close relatives

  • Smoking history: whether you’ve smoked, how much, and for how long

📌 Your answers help doctors suspect lung cancer and decide which tests to do next.

2️⃣ Physical Examination

The doctor checks your overall health by:

  • Listening to your lungs and heart

  • Measuring your temperature, blood pressure, weight, and breathing rate

  • Checking your ears, eyes, mouth, skin, and more

  • Assessing your ability to do everyday activities (called a performance status)

📌 This exam helps spot signs of disease and determine your fitness for treatment.

3️⃣ Laboratory Tests

These tests check your general health and organ function:

  • Complete Blood Count (CBC): Looks at red and white blood cells and platelets

  • Biochemistry Profile: Checks how well your kidneys, liver, and bones are working

  • Biomarker Tests: Special lab tests on tumor samples to look for changes in genes (like EGFR or ALK) that help guide treatment

4️⃣ Imaging Tests

These create pictures of the inside of your body to spot tumors and see if cancer has spread.

  • CT Scan (Computed Tomography): Detailed images of the lungs and other organs

  • PET Scan (Positron Emission Tomography): Detects areas with active cancer

  • PET/CT Scan: Combines both scans for more precise results

  • MRI (Magnetic Resonance Imaging): Especially useful for checking brain or spine

💡 Imaging can also find lung nodules by chance, even in people without symptoms.

5️⃣ Tissue and Fluid Sampling (Biopsy or Cytology)

To confirm lung cancer, doctors must look at the actual cells under a microscope. This is done by:

  • Biopsy: Removing a small piece of lung tissue

  • Cytology: Taking fluid or cell samples with a thin needle

  • Bronchoscopy: A camera is used to look inside the airways and take samples

  • Mediastinoscopy: A surgery to take samples from lymph nodes in the chest

📌 These tests are used to identify the type of lung cancer and how far it has spread.

🔬 Types of Lung Cancer (Histologic Typing)

Lung cancers are mostly carcinomas, meaning they start in the cells lining the airways. These are split into two main types:

🟣 Non-Small Cell Lung Cancer (NSCLC) – 85–90% of cases

  • Adenocarcinoma (ADC): ~40%

  • Squamous Cell Carcinoma (SCC): ~25–30%

  • Large Cell Carcinoma (LCC): ~10–15%

  • Other rare types: adenosquamous, sarcomatoid, etc.

🔵 Small-Cell Lung Cancer (SCLC) – 10–15% of cases

  • Grows and spreads faster than NSCLC

🩺 Lung Cancer Treatment Overview

Treatment for lung cancer depends on:

  • The type of lung cancer (NSCLC or SCLC)

  • The stage (how far the cancer has spread)

  • The presence of biomarkers (special features in the cancer cells)

  • The patient’s general health

Doctors use a combination of treatments to get the best results, including:

  • Surgery

  • Chemotherapy

  • Radiotherapy

  • Immunotherapy

🚭 Stop Smoking – A Key Step

If you smoke, quitting is one of the most important things you can do. Smoking can reduce the success of treatment, but cancer-related stress can make quitting harder. Your care team can support you with tools and advice to help you stop.

📝 Treatment Plan

Once your doctors confirm you have lung cancer and determine its stage, they will suggest a personalized treatment plan. The main treatment (also called primary treatment) is designed to eliminate the cancer. This could include surgery, radiation, chemotherapy, or a combination.

🔄 In some cases, more than one treatment is used to improve outcomes.

🛠️ Types of Treatment

🧪 Surgery (Mainly for Non-Small Cell Lung Cancer – NSCLC)

Surgery is often used in early-stage NSCLC, when the tumor hasn’t spread far. The surgeon removes:

  • The tumor

  • Some healthy tissue around it (to make sure no cancer is left)

  • Nearby lymph nodes, which are checked under a microscope to see if the cancer has spread

❗ Surgery is not usually used for Small-Cell Lung Cancer (SCLC) because it tends to spread quickly.

💊 Chemotherapy & Chemoradiotherapy

Chemotherapy

Uses powerful drugs to kill cancer cells throughout the body. Often used when:

  • Cancer has spread beyond the lung

  • Combined with other treatments like radiation

Common drugs: Cisplatin (often used with other medicines)

Chemoradiotherapy

This is a mix of chemotherapy and radiotherapy given together, especially for NSCLC that has spread. After this, some patients may receive a follow-up treatment with durvalumab, which helps keep the cancer under control.

🧑‍⚕️ Side effects: Tiredness, nausea, sore throat, cough, shortness of breath

🔬 Treatment for Small-Cell Lung Cancer (SCLC)

SCLC is usually treated with chemotherapy and radiotherapy, not surgery.

Because SCLC often spreads to the brain, patients may receive prophylactic cranial irradiation (PCI)—a type of radiation therapy to the brain—to prevent future spread.

☢️ Radiotherapy

Uses high-energy rays to target and destroy cancer cells in the lungs. It’s used when:

  • Surgery isn’t an option

  • Cancer is localized but surgery isn’t safe

  • Combined with chemotherapy to boost effectiveness

⚠️ Cancer cells outside the radiation area might need to be treated with chemotherapy.

🛡️ Immunotherapy

Immunotherapy helps your immune system recognize and destroy cancer cells.

Some cancers make special proteins like PD-1 or PD-L1 that hide them from immune cells. Drugs called checkpoint inhibitors block these proteins, helping your immune system attack the cancer.

These are used in specific types of lung cancer, especially those with high levels of PD-1 or PD-L1 proteins.

⚠️ Treatment Side Effects

All treatments can cause side effects. These may include:

  • Fatigue (feeling very tired)

  • Nausea or vomiting

  • Breathing difficulties

  • Sore throat or mouth

  • Weakened immune system

Your doctors will help you manage these effects and may adjust treatments to reduce discomfort.