Types of Lung Cancer

Medically Reviewed by Dr. K on 30 March 2021

Types of Lung Cancer

Small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC) are the two types of lung cancer (NSCLC). This classification is based on the appearance of tumour cells under a microscope. Making the distinction between these two forms of cancers is critical since they grow, spread, and are treated differently.

SCLC: SCLC accounts for around 10% to 15% of all lung cancers. This type of lung cancer is the most aggressive and fastest-growing of all. Cigarette smoking is strongly linked to SCLC. SCLCs spread easily throughout the body, and they are usually discovered after they have spread widely.

NSCLC: The most common type of lung cancer is non-small cell lung cancer (NSCLC), which accounts for around 85% of all cases. NSCLC is divided into three groups based on the cells present in the tumour. They are as follows:

  • Adenocarcinomas: Adenocarcinomas are the most prevalent form of NSCLC, responsible for up to 40% of lung cancer cases. Although adenocarcinomas, like other lung cancers, are linked to smoking, this form is often seen in nonsmokers, especially women, who develop lung cancer. The bulk of adenocarcinomas form in the lungs' periphery. They have a proclivity for spreading to lymph nodes and beyond. Adenocarcinoma in situ (previously known as bronchioloalveolar carcinoma) is a form of adenocarcinoma that occurs in several locations throughout the lungs and spreads along the alveolar walls. It can even appear like pneumonia on a chest X-ray. It is becoming more prevalent as a whole, and is common in women. Those who develop this form of lung cancer have a better prognosis than people who have other forms of lung cancer.
  • Squamous cell carcinomas: Squamous cell carcinomas used to be more prevalent than adenocarcinomas, but now they make up between 25% to 30% of all lung cancers. Squamous cell cancers are most common in the bronchi. This type of lung cancer tends to stay in the lung, spread to lymph nodes, and develop large enough to form a cavity.

  • Large cell carcinomas: Large cell carcinomas, also known as undifferentiated carcinomas, are the least frequent form of NSCLC, responsible for 10% to 15% of all lung cancers. This cancer has a high proclivity for spreading to lymph nodes and distant locations.

Other types of cancers

Other types of cancers can develop in the lungs; however, they are much less frequent than NSCLC and SCLC, accounting for just 5% to 10% of lung cancers:

  • Bronchial carcinoids: Up to 5% of lung cancers are caused by bronchial carcinoids. When diagnosed, these tumours are usually small (3-4 cm or less) and affect people under the age of 40 the most. Carcinoid tumours, which are unrelated to cigarette smoking, can metastasize, and a limited percentage of them secrete hormone-like compounds. Carcinoids grow and spread more slowly than bronchogenic cancers, and many may be surgically removed if diagnosed early enough.
  • Cancers of the surrounding lung tissue, such as smooth muscle, blood vessels, or immune cells, are rare in the lung.

Metastatic cancers from other primary tumours in the body are often located in the lungs.  Tumours may spread to the lungs from anywhere in the body, either by the bloodstream, lymphatic system, or directly through surrounding organs. The majority of metastatic tumours spread across the lung, and are located in the organ's periphery rather than its centre. 

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