NBME 23 Amplification (NBME Answers)

NBME 23 Answers

nbme23/Block 3/Question#21 (reveal difficulty score)
A 60-year-old woman comes to the physician 1 ...
Amplification 🔍 / 📺 / 🌳 / 📖
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submitted by ∗sympathetikey(1600)

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Per FA (pg. 636): Concerning breast cancer...

"Amplification/overexpression of estrogen/ progesterone receptors or c-erbB2 (HER2, an EGF receptor) is common; ER ⊝, PR ⊝, and HER2/neu ⊝ form more aggressive."

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sympathetikey FA 2019 +5

meningitis Why others not it: Anticipation: Trinucleotide repeats; CAG (Huntington), CTG (Myotonic dyst), GAA (ataxia telangiectasia), CGG(Fragile X) Chromosomal rearrangement: Many but can think of Trisomy 21, BCR-Abl, etc Imprinting: Prader willi, angelman Loss of heterozygosity: loss of a single parent's contribution to part of its genome. A common occurrence in cancer, it often indicates the presence of tumor suppressor gene in the lost region. +3

kai trinucleotide repeats are not associated with breast cancer Neither are chromosomal rearrangements BRCA1,2 tumor supressor genes are associated with breast cancer, which is why I chose E, but I guess I should have bought the new First Aid.......... +

charcot_bouchard GAA is Freidrich Ataxia +5

tulsigabbard So is the amplification of the receptors unrelated to BRCA 1, 2? I'm still stuck on this as Sketchy states that breast cancer falls under the "two-hit" model. +

tallerthanmymom @tulsigabbard I think one of the keys here is the question stem; " what is the most likely cause of the OVERexpression in this pts tumor cells?" --> I think that the "2-Hit" model would lead to UNDERexpression of a tumor suppression gene rather than overexpression. Whereas amplification would cause OVERexpression of the HER2/estrogen and progesterone receptors. But, I don't think that amplification would be the answer if they were asking about a triple negative cancer. +1

tallerthanmymom Also this is on page 632 of FA 2018 for those using that version +

tulsigabbard @tallerthanmymom - thank you! +

drzed I can understand why @tulsigabbard dropped out of the race--she's taking step 1 soon LOL +3

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submitted by ∗sweetmed(157)

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Gene amplification is an increase in the number of copies of a gene without a proportional increase in other genes. This can result from duplication of a region of DNA that contains a gene through errors in DNA replication and repair machinery as well as through fortuitous capture by selfish genetic elements.

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submitted by ∗imgdoc(183)

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Just wanted to add in addition to others comments, there are TWO types of breast cancer, SPORADIC (amplification, overexpression of estrogen/progesterone receptors) and then there is HEREDITARY breast cancer. IF the question stem mentioned a family history of breast cancer in say the mother or some family relative, then loss of heterozygosity would be the correct answer. What is imperative to understand is that her2/neu is a receptor tyrosine kinase, and when its over expressed on cells in the breast THAT is what leads to breast cancer. In BRCA1/2 mutations, these are tumor suppressor genes, hence they require Knudson's two hit hypothesis in order for cancer to develop. Since this question specifically mentioned HER2/neu it is safe to say that this is overexpression and has nothing to do with BRCA1/2 mutations.

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imgdoc BRCA1/2 tumor suppressors are DNA repair enzymes, and so you need to knock out both genes in order for cancer to develop. Just want everyone to know how NBME could've easily made another answer choice the correct answer. +

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