Proto-oncogenes classical

The Ewing family of tumors comprises small round cell neoplasms of bone and soft tissue that are, in part, defined by a particular chromosomal aberration [t(ll 22)] and variants thereof. Over the past 15 years, it has become clear that ES and peripheral PNET are part of the same spectrum of neoplastic proliferations. Besides the karyotypic marker just mentioned, both of those tumor types also show neuroectodermal features in tissue culture and similarities in proto-oncogene expression. As classically defined, ES was distinguished from PNET by an absence of pseudorosettes and the lack of ultrastructurally or immunohistochemically detectable neuroectodermal features. However, this diagnostic separation is now considered to be antiquated and has been abandoned. 

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