NBME 24 Normal ciliated columnar epithelium replaced by normal squamous epithelium (NBME Answers)

NBME 24 Answers

nbme24/Block 2/Question#50 (reveal difficulty score)
An obese 57-year-old man comes to the ...
Normal ciliated columnar epithelium replaced by normal squamous epithelium 🔍 / 📺 / 🌳 / 📖
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submitted by ∗lsmarshall(465)

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Metaplasia - A reversible adaptive response in which there is "Reprogramming of stem cellsreplacement of one cell type by another that can adapt to a new stress." Both are normal cells. Respiratory tree should not have squamous cells until respiratory bronchioles (before that; cuboidal in term. bron. > columnar in bronch. > pseudostratified columnar in large. bronch.).

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shayan if its a metaplasia, then how it be normal ? I mean Metaplasia is not normal? +3

artist90 i got it confused bc the question stated that there was a mass in one lobe of lung and i didn't knew that squamous metaplasia also presents as a mass in lung. i missed that on biopsy they were clearly stating squamous metaplasia. +4

suckitnbme @shayan The term "normal" in the answer is used to indicate that the cells appear normal (meaning appropriate size/architecture/appearance). Remember that metaplasia is a normal response to stress. +11

jurrutia Metaplasia is not normal (in the sense that you only have metaplasia as a reaction to stress, but under not under normal circumstances), but the cells in metaplasia are normal. When they become abnormal, you get dysplasia. +

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submitted by ∗medguru2295(64)

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they said "metaplasia"

Metaplasia= normal tissue but in an abnormal place classic example- Barrett's its NORMAL mucousa for the stomach, but in the esophagus.

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+1 upvote downvote
submitted by ∗thisshouldbefree(51)

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metaplasia - (as i learned its definition to be) - defined as replacement of one mature/normal epithelium with another mature/epithelium that is better well suited to handle stress.

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thisshouldbefree also dont forget metaplasia and even dysplasia are still reversible +1

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submitted by ∗krewfoo99(115)

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This could easily be confused with Squamous Cell Carcinoma as they are describing a mass. But i think the key difference is that they mention METAPLASIA. If it was dysplasia, then it would have been cancer.

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usmlecrasherss metaplasia also can lead to cancer FA p206 2019 +

suckitnbme Dysplasia is not cancer since it is, in theory, still reversible. Only when it becomes irreversible is it a carcinoma. +2

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