Lung cancer led world cancer deaths with 1.8 million in 2020
Lung cancer begins as malignant growth in lung tissue after DNA damage in airway cells, often from smoking or inhaled toxins. Early disease is frequently silent on symptoms and found only on imaging. In 2020 it was the most diagnosed and deadliest cancer worldwide—2.2 million cases and 1.8 million deaths.
Tobacco explains most cases; asbestos, radon, and chance mutations cover many of the rest. Before cigarettes spread in the twentieth century the disease was rare, and evidence gathered in the 1950s and 1960s led most national health bodies to warn against smoking. Diagnosis comes at about 70 on average and death at about 72; cases under forty are rare.
Growing tumours bring cough, breathlessness or chest pain, and their location adds clues. Pressure on the oesophagus makes swallowing hard, damage to laryngeal nerves causes hoarseness, and Pancoast tumours at the lung’s apex can trigger Horner’s syndrome and shoulder pain running down the little-finger side of the arm. About one patient in three already has symptoms from spread beyond the lungs.
Tumours also misbehave chemically. Many release hormones that push blood calcium dangerously high, causing nausea, thirst and confusion, or drive down potassium and sodium. Around a third of patients develop clubbed nails, up to one in twelve form abnormal clots, and autoimmune reactions such as Lambert–Eaton syndrome can weaken muscles.
Pathologists split the disease into small-cell cancer, about 15 percent of cases and usually central, and non-small-cell cancer, the other 85 percent. The latter includes adenocarcinoma at nearly 40 percent of all lung cancers, squamous-cell carcinoma near 30 percent and large-cell carcinoma under 10. A chest X-ray usually comes first, but a biopsy is needed to confirm cancer and PET scans map spread; in screening studies up to 30 percent of people show a nodule, most of them harmless. Early tumours may be removed surgically, sometimes followed by radiation or chemotherapy, while later stages rely on those treatments.
Source: Lung cancer
