Peripheral Neuroepithelioma/Primitive Neuroectodermal Tumor



Peripheral Neuroepithelioma/Primitive Neuroectodermal Tumor


Alexandros D. Polydorides, MD, PhD










Low-power view shows PNET with the classic appearance of patternless, hypercellular lobules to sheets of undifferentiated, “small round blue” cells.






High-power view shows peripheral PNET with the characteristic arrangement of monomorphic cells into nests, lobules, and cords.


TERMINOLOGY


Abbreviations



  • Primitive neuroectodermal tumor (PNET)


  • Peripheral neuroepithelioma (PNE)


Synonyms



  • Primary malignant peripheral PNET


  • Peripheral (cutaneous) neuroblastoma


  • Extraskeletal Ewing sarcoma


Definitions



  • Rare malignant small blue round cell tumor of dermis and superficial subcutis


  • Variable evidence of neuroectodermal differentiation (morphologic, ultrastructural, immunohistochemical)


ETIOLOGY/PATHOGENESIS


Histogenesis



  • Not entirely clear, regarded as controversial



    • Derived from neural crest cells or neuroepithelium of primitive neuroectodermal tissue


    • Alternatively, from primitive neuroepithelial cell


  • Considered PNET of peripheral nervous system



    • Thought to arise from peripheral nerves


    • Not connected to sympathetic nervous system


  • Morphologic similarities with other embryonal tumors



    • Assumed to share common histogenetic origins


    • Central nervous system PNET (medulloblastoma)


    • Askin tumor (chest wall/thoracopulmonary PNET)


Genetics



  • t(11;22)(q24;q12)



    • Related to Ewing sarcoma (same translocation)


    • Probably phenotypic spectrum of same tumor


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Very rare (especially if metastasis excluded)


  • Age



    • Children, adolescents, young adults (20s)


    • Occasionally may affect older patients


  • Gender



    • No gender predilection reported


Site



  • Trunk, extremities, scalp, face, neck, shoulder


  • May uncommonly involve vulva, vagina


Presentation



  • Mostly painless nodules



    • But may be tender


  • May be clinically misdiagnosed as benign tumor or cyst


  • Usually do not secrete catecholamines or metabolites


Natural History



  • Highly aggressive behavior



    • May grow rapidly


  • Distant metastases common



    • Regional lymph nodes, lung, liver, bones, brain


Treatment



  • Surgical approaches



    • Goal is complete surgical resection


  • Adjuvant therapy



    • Chemotherapy and radiation

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Peripheral Neuroepithelioma/Primitive Neuroectodermal Tumor
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