Testis & paratestis
Epididymal tumors
Melanotic neuroectodermal tumor
Author: Swapnil U. Rane, M.D.
Last author update: 1 November 2014
Last staff update: 3 August 2023
Copyright: 2003-2025, PathologyOutlines.com, Inc.
PubMed Search: Melanotic neuroectodermal tumor
Table of Contents
Definition / general | Terminology | Epidemiology | Etiology | Clinical features | Diagnosis | Laboratory | Prognostic factors | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Electron microscopy description | Differential diagnosisCite this page: Rane S. Melanotic neuroectodermal tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisepidmelanoticneuro.html. Accessed January 17th, 2025.
Definition / general
- A rare benign tumor of neuroectodermal origin with biphasic population of neuroblastic cells and pigmented epithelial cells
Terminology
- 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
Epidemiology
- 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
Etiology
- 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
Diagnosis
- Suspected clinically and confirmed histologically
Laboratory
- Urinary vanillylmandelic acid (VMA) / homovanillic acid (HVA) elevated in some cases
Prognostic factors
- Good prognosis, rarely metastasizes (Cancer 1983;52:661), does recur (Indian J Pathol Microbiol 2005;48:363)
- Local recurrence rate in jaw tumors is ~15%
- No reliable histological features predict recurrence or metastasis
Case reports
- Infant with tumor of epididymis and testis (Indian J Pathol Microbiol 2005;48:363)
- 4 month old boy with tumor in epididymis (Urol Int 1996;57:262)
- 6 month old boys (Urology 1995;46:415, Zentralbl Pathol 1994;140:181)
Treatment
- Benign behavior (Hum Pathol 1985;16:416)
- Simple orchiectomy is usually curative
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
Images hosted on other servers:
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
Images hosted on other servers:
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
- NSE, synaptophysin, HMB45, keratin
- Vimentin, GFAP, chromogranin, dopamine β hydroxylase
- Fontana-Masson stain highlights the melanin
Electron microscopy description
- Large cells contain melanosomes and premelanosomes with varied maturation while the neuroblastic cells contain neurosecretory granules and neurofilaments
Differential diagnosis
- Other round cell tumors
- Ewings / PNET
- Leukemic infiltrate
- Metastatic neuroblastoma
- Rhabdomyosarcoma: desmin, myogenin+, HMB45-
