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

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

Langerhans cell histiocytosis: morphological, immunohistochemical and ultrastructural study

A total of 23 samples of 21 patients designated Langerhan's cell histiocytosis [LCH] or eosinophilic granuloma was collected for this study. Light microscopy showed that the picture of LCHs was a mixture of Langerhan's [LCs] and eosinophils in varying proportions along with the occasional giant cells of foreign body and Langerhan's giant cells, lymphocytes and neutrophils. The immunohistochemical study showed mostly negative staining for alpha-1-antitrypsin. Out of the 23 specimens, 19 were positive for S100. CD Ia was performed on all cases with 100% positivity. The macrophages were negative for CD Ia and S100, but were positive for alpha-1-antitrypsin. The staining for NSE was positive for 19 specimens, but it was nonspecific as the histiocytes showed also a positive staining. All the 21 cases studied by electron microscopy had the characteristic features of Langerhans' cell histiocytosis in the form of Birbeck granules along with the deeply cleaved or pseudo-multisegmented nuclei with finely dispersed, thinly marginated chromatin and inconspicuous nucleoli