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May 21, 2007
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I am a little confused about these stains, could you please read this and tell me if I am off in my thinking? I dont need a super in depth explanation just whatever will suffice for step 1.

S100 stains for SCLC, medullary thyroid, melanoma, schwannoma, and carcinoid tumors correct? Essentially anything neural crest? Are there any tumors I am missing?
Also, S100 stains same things are enolase, chromogranin, synaptophysin?
S100 is a stain for "neurofilaments"?

What are the differences between these neuroendocrine/Neural crest tumors and the so called Primitive Neuro-Endocrine (blue cell) tumors (i.e. medulloblastoma) do they all stain the same thing?

Sorry, I have tried to piece this stuff together from World and FA and its not easy.


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S100 protein is a Ca++ receptor protein, with many many types/variations, found in many places in the body.

Examples: cells that are or come from myoepithelium, macrophages, neural crest, keratinocytes, adipocytes, dendritic cells, chondrocytes, Langerhan's cells, maybe breast...

So you would expect to find it in a large variety of tumors and other pathology. In addition to the neural crest stuff, it's a pretty good marker for epithelial tumors like melanoma. Seems to show up in everything from brain to uterus.


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Melanoma is not an epithelial tumor!

Do you even need to know what S100 stains for step I? I don't remember that.

S100 is thought to be a neural based protein but there is a lot of overlap and it is expressed in non-neural things like melanocytes, chondrocytes, myoepithelial cells.

S100 doesn't really stain carcinoid tumors (or other neuroendocrine tumors like medullary thyroid) - there are positive cells in these tumors but it is the supporting stromal cells and NOT the actual neuroendocrine tumor cells. The neuroendocrine tumor cells DO stain for chromogranin, synaptophysin.

S100 is not a neurofilament stain. It will stain neural supporting cells like those in neurofibromas, schwannomas, however.

If you want to know what S100 stains, just remember melanoma, neural tumors (like schwannoma, neurofibroma) and myoepithelial cells and that is most of the important areas it is used in.

For step 1 you would at most I would expect have to know something like "Ugly tumor with S100 positive cells = melanoma, spindle cell tumor with s100 positive cells = schwannoma or neurofibroma."


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Yup, total overkill. For the oncology stuff, know general big concept stuff. Don't worry about specific stains, except maybe for micro. You'll quickly forget most of these random numbers and even the heme onc attendings I have been working with don't memorize them.
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