Lung cancer
Also known as: bronchogenic carcinoma, lung carcinoma
Lung cancer is a malignant tumor arising from the tissues of the lung, most often the bronchial epithelium. It is divided into small cell and non-small cell types, and it is the leading cause of cancer death worldwide.
Malignant lung tumors are classified first as small cell lung carcinoma (SCLC) or non-small cell lung carcinoma (NSCLC), because the two behave and are managed very differently. NSCLC accounts for roughly 85% of cases and includes adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. SCLC makes up most of the remainder.
Each histologic type has a characteristic profile. Adenocarcinoma is the most common overall, arises peripherally from glandular tissue, and is the type most often seen in patients who never smoked. Squamous cell carcinoma is typically central, is strongly linked to smoking, shows keratin pearls and intercellular bridges on histology, and may cavitate; it classically secretes parathyroid hormone-related peptide, producing hypercalcemia. Small cell carcinoma is central and neuroendocrine in origin, is almost always associated with smoking, and is usually widely disseminated by the time it is found, which is why it is treated with chemotherapy and radiation rather than resection. Its paraneoplastic syndromes include SIADH, ectopic ACTH secretion causing Cushing syndrome, and Lambert-Eaton myasthenic syndrome.
Tobacco smoke is the dominant risk factor; radon exposure is the next largest contributor, and asbestos acts synergistically with smoking to multiply risk. Symptoms — persistent cough, hemoptysis, dyspnea, chest pain, and weight loss — tend to appear late, which is a principal reason for poor survival. Local invasion produces recognizable syndromes: a superior sulcus (Pancoast) tumor compressing the sympathetic chain and brachial plexus, superior vena cava syndrome from mediastinal obstruction, hoarseness from recurrent laryngeal nerve involvement, and malignant pleural effusion.
Because early disease is asymptomatic, screening targets risk rather than symptoms. Low-dose CT screening is recommended for adults within a defined age range who have a substantial smoking history, and smoking cessation counselling remains the single most effective preventive intervention.
Exam emphasis differs by credential. USMLE Step 1 concentrates on histologic subtypes, their typical locations, and their paraneoplastic associations. The CCMA covers lung cancer within tobacco use and chronic respiratory disorders. NCLEX approaches it from health promotion and maintenance, testing cancer screening recommendations and lifestyle counselling for high-risk behaviours.
Key takeaways
- Lung cancer is divided into small cell and non-small cell carcinoma, which differ in behavior and treatment.
- Adenocarcinoma is the most common type and typically peripheral; squamous cell carcinoma is typically central.
- Small cell carcinoma is neuroendocrine, usually disseminated at diagnosis, and associated with SIADH, ectopic ACTH, and Lambert-Eaton syndrome.
- Smoking is the leading risk factor, followed by radon, with asbestos acting synergistically.
- Symptoms appear late, so low-dose CT screening targets high-risk adults defined by age and smoking history.