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.



  • Primitive neuroectodermal tumor (PNET)

  • Peripheral neuroepithelioma (PNE)


  • Primary malignant peripheral PNET

  • Peripheral (cutaneous) neuroblastoma

  • Extraskeletal Ewing sarcoma


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

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



  • 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)


  • t(11;22)(q24;q12)

    • Related to Ewing sarcoma (same translocation)

    • Probably phenotypic spectrum of same tumor



  • Incidence

    • Very rare (especially if metastasis excluded)

  • Age

    • Children, adolescents, young adults (20s)

    • Occasionally may affect older patients

  • Gender

    • No gender predilection reported


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

  • May uncommonly involve vulva, vagina


  • 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


  • 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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