NBME 22 Lung cancer (NBME Answers)

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Retired NBME 22 Answers

nbme22/Block 1/Question#31 (reveal difficulty score)
A 60-year-old woman comes to the physician ...
Lung cancer 🔍 / 📺 / 🌳 / 📖
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submitted by ∗atstillisafraud(217)

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Weight loss - think cancer Hyponatremia - SIADH from small cell lung cancer Edema + JVD - SVC syndrome

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peridot I was thinking lung cancer secreting SIADH, resulting in hyponatremia. But because the question asked specifically about the cause of the facial edema, I put hyponatremia (answer choice C). I was wondering how you guys were able to differentiate between C. hyponatremia and E. lung cancer? Thank you! +2

mannan The first thing that crossed my mind was SVC syndrome from the cancer obstructing the R brachiocephalic vein preventing venous blood from returning to the heart (and staying in the facial area). Also I assume Hyponatremia would be equivalent to decreased body volume so there wouldn't be edema. FA Renal physiology section has a good chart on what happens during electrolyte imbalances (hypo and hyper) +2

mannan @peridot +2

peridot I was thinking that hyponatremia would be more loss of osmotic pressure --> edema, but I definitely see the argument for a mass that's simply blocking blood flow. Thank you! +1

jaramaiha only thing affecting osmotic pressure is albumin, which would be more towards liver cirrhosis. The body will attempt to maintain a Na+ of 140 with various mechanisms, but doesn't contribute to osmotic pressure. +1

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submitted by ∗thirdaid(10)

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The initial presentation looks like cancer: weight loss and progressive dyspnea over the course of months in a heavy smoker. Then, the question describes extra-pulmonary symptoms and a paraneoplastic syndrome.

More acutely, there is development of edema of the face and jugular venous distention. Because this is localized to upper body, we should think of a mechanical obstruction to venous flow as opposed to some cardiogenic reason. This is an extra-pulmonary symptom of lung cancer.

[ Superior Vena Cava Syndrome caused by the medial spreading of the tumor. Can be exacerbated in the physical exam by asking patient to raise both arms. ]

Finally, there is a single highlighted lab value -> hyponatremia. Small cell lung cancer can release inappropriate levels of antidiuretic hormone -> SIADH. ADH will retain water and decrease sodium concentration possibly leading to cerebral edema and seizures.

[ Syndrome of Inappropriate ADH (due to small cell carcinoma, a neuroendocrine tumor of the lung) decreases sodium concentration. Paraneoplastic syndrome. ]

In SketchyPath: SVC syndrome is the red balloon near the mediastinum ship and SIADH is the guy trying to carry the water cooler and getting water all over himself.

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makinallkindzofgainz I agree! Superior sulcus tumors is a lung carcinoma that occurs in the apex of the lung and can cause SVC syndrome. +2

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submitted by ∗agraham416(5)

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am i the only dumb one who thought it was angioedema cause of the ACE inhibitor? totally neglected all other information.

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dwdelva8 I did the same thing, but she had been on that ACE inhibitor for 15 years so I guess it would be strange for it to all of sudden cause symptoms +

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submitted by ∗ekraymer(1)

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Was it wrong to see blood tinged sputum, and automatically assume its cancer? since none of the others would have caused blood tinged sputum?

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