lung cancer
Meaning of lung cancer: Tobacco smoke drives most cases, yet the disease also arises in people who never smoked, usually as adenocarcinoma.
Definition of lung cancer
Lung cancer is cancer that begins in the tissue of the lung, most often in the cells lining the airways. It is among the most commonly diagnosed cancers worldwide and the leading cause of death from cancer. It falls into two broad groups, non-small cell and small cell, told apart by how the cells appear under a microscope.
What are the two main types?
| Non-small cell | Small cell | |
|---|---|---|
| Share of cases | The large majority | The smaller share |
| Main subtypes | Adenocarcinoma, squamous cell carcinoma, large cell carcinoma | Treated as one group |
| Usual position | Adenocarcinoma toward the outer lung, squamous nearer the central airways | Usually central, near the large airways |
| Pace | Slower, often localized when found | Fast growing, commonly spread at diagnosis |
| Link to smoking | Strong, but a substantial minority never smoked | Very strong; rare in people who never smoked |
Adenocarcinoma is now the most common single subtype and the form most often seen in people with no smoking history. Small cell tumors sometimes announce themselves indirectly, by releasing hormone like substances that disturb sodium levels or produce muscle weakness before the tumor itself causes symptoms.
What raises the risk?
Tobacco smoke is the dominant cause, and risk climbs with the amount and duration of smoking while falling steadily after stopping, though never quite back to the level of someone who never smoked. Second hand smoke raises risk too. Radon, a colorless radioactive gas seeping from soil into buildings, is the next largest contributor. Asbestos, certain metals and diesel exhaust act as occupational exposures, and asbestos combined with smoking multiplies risk rather than adding to it. Outdoor air pollution, previous radiation treatment to the chest, scarring from earlier lung disease and a family history all contribute.
Why does the subtype decide so much?
The two groups behave so differently that they are handled as separate diseases. Small cell disease spreads early and is described in most settings simply as limited or extensive. Non-small cell disease is staged in detail, and its tissue is tested for specific genetic changes and for markers on the tumor surface, because a tumor carrying one of those changes may respond to a drug aimed precisely at it. Establishing the type and the molecular profile therefore comes before any treatment plan is settled.
Used in a sentence
Imaging and biopsy findings established a diagnosis of non-small cell lung cancer.
Good to know
Small cell and non-small cell lung cancer follow different treatment approaches and different staging systems, so the distinction between them is settled before a treatment plan is determined.