These aggressive neoplasms tend to arise in the muscularis propria
of the ileum of young adults. Spread to the liver and other sites is common and
there is poor response to current therapy.
They can have a nested or pseudopapillary pattern. The pitfall is that they
are easy to mistake for well-differentiated neuroendocrine tumors owing to
their proclivity to express synaptophysin. Keratin expression, however, is
absent and they are strongly reactive for S100 protein. Some examples, such as this one, feature
macronucleoli, which makes their morphology similar to that of clear cell
sarcoma of soft tissue. Most such gastrointestinal
fusions and lack expression of markers of melanocytic differentiation whereas
soft tissue clear cell sarcomas usually have
EWSR1-ATF1 rearrangements and stain with melanoma markers.
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Cin P, Ladanyi M. EWS-CREB1: a recurrent variant fusion in clear cell
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Spagnolo D, Dominguez-Malagon H, Hornick JL, Adsay V, Chou PM, Amanuel B,
Vantuinen P, Zambrano EV. Malignant gastrointestinal neuroectodermal tumor:
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gastrointestinal tract. Am J Surg Pathol. 2012 Jun;36(6):857-68.
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malignant gastrointestinal neuroectodermal tumour: distinct or related
entities? A review. Pathology. 2018 Aug;50(5):490-498.