Ewing's sarcoma, primitive neuroectodermal tumour and neuroblastoma: morphological, immunohistochemical and electron microscopic study

ABSTRACT

Ewing's sarcoma [ES], primitive neuroectodermal tumour [PNET] and neuroblastoma [NB] are most commonly considered in the differential diagnosis of small blue round cell tumor of infancy and childhood. The differential diagnosis between these over- lapped tumours is of utmost importance for therapy and prognosis. The aim of this study was to assess the morphological, immunohistochemical and ultrastructural diagnostic features of these overlapping tumors. The study was done on 18 cases including eight cases of Ewing's sarcoma, ES [seven bone and one soft tissue], three cases of primitive neuroectodermal tumor [PNET] and seven cases of neuroblastoma, NB [all were primary tumors]. ES was diagnosed by its positivity for CD 99, the presence of glycogen either histochemically or by EM along with the classic morphology of ovoid cells lacking rosettes and spindle cell pattern. NB was diagnosed by its positivity for neuron specific enolase [NSE] and negativity for CD 99, the presence of neurites, neurosecretory granules and neuropils by EM along with the rosettes by light microscopy and the absence of glycogen both histochemically and by EM. PNET had some features of ES as the presence of glycogen and positivity for CD 99 as well as some features of NB as the positivity for NSE and the presence of neurosecretory granules and neurites as well as the occasional presence of rosettes by light microscopy