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NBME 16 Answers

nbme16/Block 1/Question#2 (reveal difficulty score)
A 66-year-old man has a surgical excision of ...
Kidney ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–

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 +20  upvote downvote
submitted by โˆ—cassdawg(1779)

This is metastatic renal cell carcinoma (FA2020 p605) for the following reasons:

  • Polycythemia - this is the primary clue, as it is associated with ectopic EPO (erythropoitin) secretion in paraneoplastic syndromes (FA2020 p228), which can be caused by pheochromocytoma, renal cell carcinoma, heptocellular carcinoma, hemangioblastoma and leiomyoma. Of these, only liver and kidney would be a choice given and hepatocellular carcinoma is incorrect because he did not have any associated finding of jaundice, hepatomegaly, ascites, or anorexia (FA2020 p392). Plus, the liver does not commonly metastasize to brain whereas kidney does (FA2020 p223)
  • Hypercalcemia - this is likely indicative of PTHrP secretion, and renal cell carcinoma is one of the cancers that can do this. However, this is fairly nonspecific as there are many cancers that can secrete PTHrP.
  • Heamaturia - suggestive of kidney/urinary tract involvement
  • Negative for carcinoembryonic antigen - this is a nonspecific marker mainly for colon and pancreatic cancers (FA2020 p226)
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hungrybox  WOW. Amazing explanation. Great work!! +
nbmeanswersownersucks  Additionally the histo looks like the Clear cell type of RCC. The large white/clear spaces with "chicken-wire" vessels and stroma between them. +11
hecticsurreyguy  Any idea as to how the " positive epithelial membrane antigen" fits into it being renal cell carcinoma? Also to add to the reasons for it being Kidney, the image that they provide is a classic example of renal cell carcinoma cells. Take note of how the cells look to almost be vacuolated or completely clear of any cytosolic material apart from the nucleus. This the classic presentation for renal "clear cell" carcinoma. +

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