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NBME 21 Answers

nbme21/Block 4/Question#5 (reveal difficulty score)
An 11-year-old boy has had persistent pain in ...
Lung ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–

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 +34  upvote downvote
submitted by โˆ—jambo2222(34)
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Itโ€™s an osteosarcoma. Sarcoma = hematogenous mets. Itโ€™s in the legs so think how a DVT goes to lung. Same idea.

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tinydoc  Perfect way to remember it. Thank you! +11
chandlerbas  Iused the mnemonic PB (lead) KeTtLe....looking at the stem it said "osteolytic mass" meaning that it has to be either Breast, Kidney, thyroid or lungs. none of the rest are options leaving lungs. but jambo2222 very noiice that works too! +1
jajajaja  @chandlerbas I think you might be using the mneumonic backwards- PB-KTL is for primary cancers that met to bone. For example, a primary lung cancer can met to bone and cause an osteolytic lesion. But in this case the primary cancer is the osteosarcoma. Meaning that the mneumonic doesn't actually apply to this question +18
chandlerbas  ya you're right good stuff!! I dont know why that made sense during the question...anyways to add to the other comments...osteosarcomas are aggressive and 10% metastasize to the lungs via hematogenously at the time of diagnosis. +
mtkilimanjaro  just to add, in terms of venous circulation everything goes to heart via vena cava and then to the lungs. The only way the bone would metastasize to these other structures would be if it continued through arterial circulation without seeding, which seems unlikely. The only ones that spread to the liver are from the PORTAL venous system, aka not bone only colon etc. +3

 +4  upvote downvote
submitted by โˆ—cellgamesgojan(43)
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Jambo is right. I was reading through Goljan Rapid Review and he states that the lungs are the most common site of metastasis for osteosarcoma.

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 -6  upvote downvote
submitted by โˆ—meryen13(48)
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Painful Bones Kill The Lungs: Prostate,Breast> Kidney, Thyroid, Lung thats the mnemonic in FA 2020 for primary tumors that may metastasize in the bone.

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balerion  Ya, but its asking where a primary bone lesion metastasizes to. Not lung -> bone +3

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