Lung cancer

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Lung cancer

Respiratory system


Lung cancer


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USMLE® Step 1 questions

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Lung cancer

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USMLE® Step 1 style questions USMLE

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A 65-year-old man is brought to the emergency department because of abdominal pain and altered mental status. His partner states he has a history of lung cancer, which is currently being treated with chemotherapy. The partner also states that over the past week the patient has seemed “more confused,” and he was frequently going to the bathroom to urinate. Temperature is 37.0°C (98.6 °F), pulse is 102/min, respirations are 20/min, and blood pressure is 105/65 mmHg. Physical examination reveals dry mucous membranes and decreased skin turgor. ECG is obtained and shows shortened QT-intervals, as well as positive deflection at the junction of the QRS-complexes and ST-segments in leads V1-V6. Which of the following is the most likely responsible for this patient’s observed ECG changes?  

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ALK gene p. 222

lung cancer p. 707


lung cancer and p. 709

Bronchogenic apical lung tumor p. 723

Bronchogenic carcinoma

asbestosis and p. 702

carcinogens causing p. 223

Cough p. 148, 572

lung cancer p. 709


lung cancer p. 709


lung cancer p. 709

Horner syndrome p. 530, 536, 559

lung cancer p. 709

Hypercalcemia p. 615

lung cancer p. 709

KRAS gene p. 222

lung cancer and p. 707

Lung cancer p. NaN

apical tumor p. 723

asbestosis and p. 702

carcinogens causing p. 223

cisplatin/carboplatin for p. 448

erlotinib for p. 451

hypercalcemia and p. 221

incidence/mortality in p. 202

metastases to p. 224

oncogenes and p. 222

paraneoplastic syndromes and p. 221

SIADH p. 732

topotecan for p. 450

Metastases (lung cancer) p. 707

Pancoast tumor p. 710

lung cancer p. 709

Paraneoplastic syndromes p. 221

lung cancer p. 709

Pleural effusion p. 302

lung cancer p. 707


lung cancer p. 709

Small cell (oat cell), lung cancer p. 707


lung cancer p. 709

Superior vena cava syndrome p. 96, 710

lung cancer p. 709


lung cancer p. 709


Lung cancer, or lung carcinoma, is the uncontrolled division of epithelial cells which line the respiratory tract. There are two main categories of lung cancer: small cell and non-small cell which depend on the type of epithelial cell that’s dividing. Both types can be fatal, especially if the cancerous cells aggressively spread and establish secondary sites of cancer in other tissues. The major cause of lung cancer is smoking tobacco products, and has contributed to the deaths of millions of people, including famous individuals like Walt Disney and Claude Monet.

Now, air enters the respiratory tract through either the nose or mouth, and flows down the trachea, which divides into the right and left bronchi. Each bronchus enters its respective lung at the hilum, or the root of the lung. The bronchi then divides into lobar bronchi, which divide into segmental bronchi, and then into subsegmental bronchi which further branch to form conducting bronchioles, and then respiratory bronchioles which end with small sacs called alveoli that are surrounded by capillaries, which is where gas exchange happens.

Lining these airways are several types of epithelial cells which serve multiple functions. These include ciliated cells that have hairlike projections called cilia that work to sweep foreign particles and pathogens back to the throat to be swallowed. Another type called Goblet cells, which are called that because they look like goblets, secrete mucin to moisten the airways and trap foreign pathogens. There are also basal cells that are thought to be able to differentiate into other cells in the epithelium, club cells that act to protect the bronchiolar epithelium, and neuroendocrine cells that secrete hormones into the blood in response to neuronal signals.

Cells can become mutated because of environmental or genetic factors. A mutated cell becomes cancerous when it starts to divide uncontrollably. As cancer cells start piling up on each other, they become a small tumor mass, and they need to induce blood vessel growth, called angiogenesis, to supply themselves with energy. Malignant tumors are ones that are able to break through the basement membrane. Some of these malignant tumors go a step further and detach from their basement membrane at the primary tumor site, and then enter nearby blood vessels, and establish secondary sites of tumor growth throughout the body—a process called metastasis.


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  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw Hill Professional (2019)
  5. "Hallmarks of Cancer: The Next Generation" Cell (2011)
  6. "Lung carcinogenesis by tobacco smoke" International Journal of Cancer (2012)
  7. "K-ras Mutations in Non-Small-Cell Lung Carcinoma: A Review" Clinical Lung Cancer (2006)

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