The type of lung cancer you have tells you the cell of origin. This helps the doctor decide the appropriate treatment plan.
Primary lung cancer is when cancer has originated from the lung.
The different types of primary lung cancer are divided into two main types:
- Small cell lung cancer
- Non-small cell lung cancer
The most common type of lung cancer is non-small cell cancer.
Small cell lung cancer
15 to 20% of all lung cancers are of the small cell type. The leading cause for small cell carcinoma is smoking, and these cancers usually spread early on.
Non-small cell lung cancer
80 to 85% of people with lung cancer have non-small cell lung cancer. The main types of non-small cell carcinoma are squamous cell carcinoma, adenocarcinoma, and large cell carcinoma.
These cancers are grouped together because they progress in a similar manner, and they all respond to the same treatment.
Adenocarcinoma: This is the most common type of non-small cell lung cancer. These cancers are usually seen at the periphery of the lung. This originates from the mucus-producing cells of the lungs.
Squamous cell carcinoma: These cancers tend to grow near the centre of the lung and arise from the cells that line the airways.
Large cell carcinoma: This is relatively less common, and on microscopy, the cells are large and round.
Other primary lung cancers include tumours that are rarely found such as:
- Salivary gland tumours
- Lung lymphoma
- Lung sarcoma
Treatment for such tumours is different from other non-small cell cancers.
Diagnosing lung tumours
Treatment for a patient with lung cancer is decided based on the histology, stage, general health, and comorbidities of the patient. Investigations of patients with suspected lung cancer are done to identify the sub-type and to determine the length of the spread of the disease.
- History – Duration of symptoms, other comorbidities, family history of cancer, history of smoking, or inhaling second-hand smoke.
- Physical examination – This helps to assess the general well-being of the patient as well as to look for signs of Paraneoplastic Syndromes like nerve damage leading to drooping of an eye-lid or clubbing of fingernails.
- Routine laboratory evaluations, such as haemoglobin levels, liver, and kidney function tests – This also helps in assessing if the patient is going to be able to withstand chemotherapy or radiotherapy if it has to be given.
- Chest x-ray – This is a preliminary test for all respiratory disorders, and if lung cancer is suspected.
- Chest CT (Computed Tomography) – This is usually done after the infusion of a contrast dye and the multiple slices that are taken help to estimate the tumour burden accurately.
- :PET-CT- This is a whole body scan that helps to determine the spread of cancer- It helps us understand the stage of cancer.
- Lung biopsy – A lung biopsy is usually done under the guidance of Computed Tomography or an MRI (Magnetic Resonance Imaging). This is the gold standard for diagnosis, as the histological type can be determined on the obtained tissue.
- Bronchoscopy and biopsy- In some tumors, especially for central tumors of the lung, the biopsy may be obtained with the help of a scope guided into the airway by a trained pulmonologist.
Dr. Pragnya Coca, Consultant Medical Oncology, Oncology, Mazumdar Shaw Medical Center, Bommasandra, Bangalore