Lung Cancer: Step 1 review notes and self-test
Notes for the Lung Cancer rapid review: the clue that separates each of its 4 confusion pairs, with timestamps and a self-test.
October 21, 2026
This video covers key confusion pairs in lung cancer and sleep apnea. Watch it, then use these notes to test yourself on the clue that separates each pair.
Squamous cell carcinoma of lung vs Adenocarcinoma of lung
You separate them by location and histology: squamous is central or hilar, often cavitary, with keratinization, intercellular bridges, and PTHrP-mediated hypercalcemia, while adenocarcinoma is often peripheral, gland-forming, or mucin-producing. Do not rely on smoking history alone because adenocarcinoma also occurs in smokers.
Squamous cell carcinoma of lung vs Adenocarcinoma of lung Squamous is central cavitary PTHrP; adenocarcinoma is peripheral gland-forming/mucin-producing. Open the comparison and video →Small cell lung cancer vs Non-small cell lung cancer
You identify small cell by central neuroendocrine behavior, early metastasis, scant cytoplasm, nuclear molding, and SIADH or ectopic ACTH, while non-small cell is an umbrella category classified by subtype, stage, histology, and molecular markers. Do not assume every central lung mass is small cell.
Small cell lung cancer vs Non-small cell lung cancer Small cell is central neuroendocrine and systemic early; non-small cell is subtype-driven and often staged for local versus systemic treatment. Open the comparison and video →Pancoast syndrome vs Superior vena cava syndrome
You separate Pancoast syndrome by shoulder or medial arm pain, hand weakness, and Horner syndrome from superior vena cava syndrome with face, neck, or upper-extremity swelling, venous distention, and chest wall collateral veins. Both can result from lung cancer, so do not stop at finding a thoracic mass.
Pancoast syndrome vs Superior vena cava syndrome Pancoast: apical tumor with arm pain and Horner syndrome; SVC syndrome: facial plethora, JVD, and upper-body edema from venous obstruction. Open the comparison and video →Obstructive sleep apnea vs Central sleep apnea
You separate obstructive sleep apnea by continued respiratory effort against a collapsed upper airway from central sleep apnea by absent airflow and absent respiratory effort. Do not rely on snoring or sleepiness because respiratory effort is the sleep-study separator.
Obstructive sleep apnea vs Central sleep apnea Obstructive sleep apnea: apneas with continued respiratory effort; central sleep apnea: apneas with absent respiratory effort. Open the comparison and video →Quick self-test
Name the diagnosis from the clue, then tap to check.
Smoking-associated central or hilar tumor, often cavitary, with keratinization/intercellular bridges and PTHrP-mediated hypercalcemia.
Squamous cell carcinoma of lung · Squamous cell carcinoma of lung vs Adenocarcinoma of lung
Aggressive central neuroendocrine lung cancer in smokers with early metastasis, scant cytoplasm, nuclear molding, and paraneoplastic SIADH or ectopic ACTH.
Small cell lung cancer · Small cell lung cancer vs Non-small cell lung cancer
Often peripheral gland-forming or mucin-producing tumor; most common lung cancer overall and common in nonsmokers.
Adenocarcinoma of lung · Squamous cell carcinoma of lung vs Adenocarcinoma of lung
Umbrella category including adenocarcinoma, squamous cell carcinoma, and large cell carcinoma, often managed by stage, histology, and molecular markers.
Non-small cell lung cancer · Small cell lung cancer vs Non-small cell lung cancer
Apical superior sulcus tumor invading brachial plexus and sympathetic chain, causing shoulder/medial arm pain, hand weakness, and Horner syndrome.
Pancoast syndrome · Pancoast syndrome vs Superior vena cava syndrome
Keep going
Every pair in this review has a free page in the library with a side-by-side comparison and a practice question. Work through the ones you missed in the self-test first.