Ewing’s sarcoma/primitive neuroectodermal

Qian X, Jin L, Shearer BM, et al. Molecular diagnosis of Ewing s sarcoma/primitive neuroectodermal tumor in formalin-fixed paraffin-embedded tissues by RT-PCR and fluorescence in situ hybridization. Diagn Mol Pathol. 2005 14 23-28. 

The best-known association between FEI-1 and human tumors relates to its fusion with the EWS gene on chromosome 22 (22ql2) in many examples of Ewing s sarcoma/ primitive neuroectodermal tumor (PNET).i An associated fusion protein results from that event, which probably plays a role in the evasion of cellular senescence. 

Folpe AL, Hill CE, Patham DM, O Shea PA, Weiss SW. Immunohistochemical detection of FLI-1 protein expression A study of 132 round-cell tumors with emphasis on GD99-positive mimics of Ewing s sarcoma/primitive neuroectodermal tumor. Am J Surg Pathol. 2000 24 1657-1662. 

Vakar-Lopez F, Ayala AG, Raymond AK, Czerniak B. Epithelial phenotype in Ewing s sarcoma/primitive neuroectodermal tumor. Int J Surg Pathol. 2000 8 59-65. 

Mhawech-Fauceglia P, Herrmann E, Penetrante R, et al. Diagnostic utility of FLI-1 monoclonal antibody and dual-colour, break-apart probe fluorescence in situ (FISH) analysis in Ewing s sarcoma/primitive neuroectodermal tumour (EWS/PNET). A comparative study with CD99 and ELI-1 polyclonal antibodies. Histopathology. 2006 49(6) 569-575. 

Neuroblastomas are small, round, blue cell tumors that may arise in the adrenal gland and a variety of extra-adrenal sites. The differential diagnosis is wide and includes rhabdomyosarcoma, Ewing s sarcoma-primitive neuroectodermal tumor (ES-PNET), medulloblastoma, small cell osteosarcoma, lymphoblastic lymphoma, blastematous Wilms tumor, and small cell desmoplastic tumor. Numerous markers have been used for the diagnosis of neuroblastomas including NE markers, cytoskeletal proteins, catecholamine-synthesizing enzymes, and neuroblastoma-"specific antibodies (Eig. 

CD99 is a useful marker for the distinction of neuroblastomas from other small, round, blue cell tumors. More than 100 cases of neuroblastoma have now been studied for CD99, and all have been negative. In contrast, nearly 100% of cases of Ewing s sarcoma-primitive neuroectodermal tumor (ES-PNET) are CD99-positive. Anti-Pi-microglobulin is another marker that is negative in neuroblastoma but positive in approximately 75% of ES-PNET. ... 

In addition to the small-cell tumors presented in the foregoing sections, others of a metastatic nature also may involve the mediastinum. These include small-cell osteosarcoma and Ewing s sarcoma/primitive neuroectodermal tumor (PNET) of bone, as well as small-cell malignant melanoma. Except for the last of these possibilities, the primary lesion in such cases is typically obvious and there is no question of whether the intra-thoracic neoplasm might have arisen there. Nonetheless, melanomas are certainly capable of producing distant metastasis in the absence of an obvious primary source. 

FIGURE 17.14 Ewing s sarcoma/primitive neuroectodermal tumor displays cohesive sheets of small- to medium-sized round cells with round to oval nuclei, fine chromatin, scant clear cytoplasm, and indistinct cell borders (hematoxylin-eosin, x200). 

FIGURE 17.16 CD99 (013) reactivity in Ewing s sarcoma/primitive neuroectodermal tumor typically shows a strong membranous and cytoplasmic staining pattern (immunoperoxidase x400). 

FIGURE 17.15 An immunohistogram of Ewing s sarcoma/primitive neuroectodermal tumor. 

FIGURE 17.17 Neuron-specific enolase is frequently positive in Ewing s sarcoma/primitive neuroectodermal tumor but can be seen in many other tumors (immunoperoxidase, x400). 

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