Testis & paratestis

Epididymal tumors

Melanotic neuroectodermal tumor of epididymis

Last author update: 1 November 2014
Last staff update: 28 March 2022

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PubMed Search: Melanotic neuroectodermal tumor [title]

Swapnil U. Rane, M.D.
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Cite this page: Rane S. Melanotic neuroectodermal tumor of epididymis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisepidmelanoticneuro.html. Accessed August 17th, 2022.
Definition / general
  • A rare benign tumor of neuroectodermal origin with biphasic population of neuroblastic cells and pigmented epithelial cells
  • First described by Krompecher in 1918 as congenital melanocarcinoma of alveolar process of maxilla (BMJ Case Rep 2010 Nov 23;2010)
  • Previously known as: melanotic adamantinoma, melanotic hamartoma, melanotic progonoma, pigmented congenital epulis, pigmented neuroectodermal tumor, retinal anlage tumor, retinoblastic teratoma
  • Rare
  • Usually young infants (mean 7 months, range 3 months to 8 years) but also reported in adults
  • Most common in maxilla of infants with 2:1 female preponderance (see Mandible - Maxilla Chapter)
  • Also reported in long bones (Cancer 1983;52:661), uterus, skin and brain
  • Epididymis is uncommon site
  • Precise origin is unknown but suggested to be of neural crest origin, due to a developmental error in evolution of mesonephric ducts, where neural crest cells migrate (J Pathol Bacteriol 1967;93:549)
  • A dysembryogenetic neoplasm that recapitulates embryonic retinal development (Am J Surg Pathol 1991;15:233)
  • Relationship with other neural crest tumors such as PNET, neuroblastoma, etc. is not clear
Clinical features
  • Firm, rapidly enlarging mass, sometimes associated with hydrocele
  • Usually noticed at birth or within the first year of life
  • Lymphatic space invasion is associated with hydrocele formation
  • Suspected clinically and confirmed histologically
  • Urinary vanillylmandelic acid (VMA) / homovanillic acid (HVA) elevated in some cases
Prognostic factors
Case reports
Gross description
  • Round to oval, circumscribed, firm epididymal mass, usually < 4 cm
  • Cut surface is grey white with areas of pigmentation; color depends on amount of pigmentation
Gross images

Maxillary tumors

Microscopic (histologic) description
  • Appears to recapitulate retina at 5 weeks of gestation
  • Contains dual population of cells: neuroblastic cells with high nuclear cytoplasmic ratio and epithelioid cells containing melanin
  • Mitoses may be present, usually in neuroblastic component
Microscopic (histologic) images

Maxillary tumor: H&E and stains

Cytology description
  • Dual cell population with dyscohesive primitive neuroblast like cells in fibrillary background, admixed with clusters of larger cells having melanin pigment (Acta Cytol 2006;50:460)
Positive stains
Negative stains
Electron microscopy description
  • Large cells contain melanosomes and premelanosomes with varied maturation while the neuroblastic cells contain neurosecretory granules and neurofilaments
Differential diagnosis
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