Lung cancer is the third most common cancer in the United States. Each year, about 225,000 people in the country are diagnosed.

Doctors classify lung cancer into types depending on the way cancer cells appear under a microscope and the kind of cells it develops in.

Keep reading for an overview of both common and rare types of lung cancer.

More than 95 percent of lung cancers fall into one of the two broad categories called small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Common types of lung cancer include:

  • Non-small cell lung cancer. Smoking is the main risk factor for all types of NSCLC. NSCLC cells appear large under a microscope and most commonly fall into one of these subcategories:
    • Squamous cell lung carcinoma. Squamous cell lung carcinoma develops in the cells that line the major air passages of your lungs called bronchi.
    • Lung adenocarcinoma. Adenocarcinoma develops in the cells that produce mucus.
    • Adenosquamous carcinoma. This cancer develops in a mixture of squamous cells and mucus-producing cells.
    • Large cell carcinoma. Large cell carcinoma is a group of cancers that can’t be classified as SCLC, adenocarcinoma, or squamous cell carcinoma.
  • Small cell lung cancer. Small cell lung cancers tend to develop quickly. The two main types of SCLC are:
    • Small cell carcinoma. Cancer cells appear small under a microscope.
    • Combined small cell carcinoma. A type of tumor that grows in your lung tissue that contains a mixture of SCLC and NSCLC features.
  • Lung nodule. A lung nodule is an abnormal mass in your lungs that can be seen with a CT scan. They’re usually not cancerous.
  • Metastasized cancers. Cancers that spread from other parts of your body are known as metastasized cancers. They aren’t considered lung cancers, but a form of the original type of cancer.

These lung cancers are less common but make up a small percentage of all lung cancers:

  • Carcinoid tumors. Carcinoid tumors are tumors that grows in neuroendocrine cells that produce hormones and receive signals from your nervous system.
  • Pancoast tumor. A Pancoast tumor forms at the top point of your lung and can invade your surrounding nerves or tissue.
  • Mesothelioma. Mesothelioma is a rare type of cancer caused by asbestos exposure.
  • Chest wall tumors. Chest wall tumors form on the wall of your chest cavity and can be cancerous or non-cancerous.
  • Pulmonary sarcomatoid carcinoma. A rare NSCLC that makes up about 0.1 to 0.4 percent of lung cancers. It develops in epithelial cells that line your lungs and mesenchymal cells that become connective tissues.
  • Adenoid cystic carcinoma of the lung. A rare cancer that forms in glands in your airway.
  • Lymphoma. A type of lymphoma called mucosa-associated lymphoid tissue can develop in your lungs.
  • Lung sarcomas. Sarcomas are a rare group of tumors that originate in mesenchymal cells that become connective tissue.
  • Mediastinal tumor. Mediastinal tumors form in the area between your lungs.