Melanotic Neuroectodermal Tumor



Melanotic Neuroectodermal Tumor


Steven S. Shen, MD, PhD

Jae Y. Ro, MD, PhD










Melanotic neuroectodermal tumor shows a paratesticular cellular tumor, which is well demarcated from the adjacent testis image. It is characterized by sheets of small blue cells in a fibrous background.






High-power image shows a melanotic neuroectodermal tumor involving epididymis image. There are clusters of small blue cells image and large epithelioid cells with brown pigment image.


TERMINOLOGY


Synonyms



  • Retinal anlage tumor, melanotic progonoma, melanotic hamartoma


Definitions



  • Rare paratesticular (usually epididymal) tumor of neural crest origin in infants and young children


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Extremely rare


    • < 1 dozen cases reported in testis or epididymis (more common in jaw)


  • Age



    • Range: 4 months to 8 years (80% younger than 1 year old)


Presentation



  • Firm mass in epididymis; may be associated with hydrocele


Laboratory Tests



  • Mild elevation of serum α-fetoprotein, urine vanillylmandelic acid (VMA), and homovanillic acid in some cases


Treatment



  • Surgical resection, occasionally with adjuvant therapy (chemotherapy or radiotherapy)


Prognosis



  • Generally behaves in benign fashion with rare recurrence and metastasis


MACROSCOPIC FEATURES


General Features



  • Round to oval homogeneous white-gray to bluish firm nodule


  • May show dark brown or black areas due to pigmentation


  • Closely apposed to, but usually does not involve, testicular parenchyma


Size



  • Usually < 4 cm


MICROSCOPIC PATHOLOGY


Histologic Features



  • Distinct biphasic tumor composed of 2 types of cells



    • Small neuroblast-like round cells with scant cytoplasm forming sheets or irregularly shaped nests


    • Large polygonal epithelioid cells with abundant eosinophilic cytoplasm, large vesicular nuclei, small nucleoli, and variable amounts of melanin deposits


  • Large cells may form nests, cords, and gland-like structures


  • Typically prominent fibrous and hyalinized stroma


Predominant Pattern/Injury Type



  • Biphasic with sheets of small round cells and large polygonal cells with melanin pigment


Predominant Cell/Compartment Type



  • 2 cell components: Small cells, and large cells with melanin pigment



ANCILLARY TESTS


Immunohistochemistry

Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Melanotic Neuroectodermal Tumor
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