Neuronal Embryonal Tumors in Fish

Abstract

This article describes 11 cases of neuronal embryonal neoplasia in captive adult teleost fish. Neoplasms were located within 1 or both eyes of 8 fish and the skin of 3 other fish. Ocular neoplasms most often presented as unilateral or bilateral exophthalmia. Seven ocular and 1 cutaneous mass were composed of small triangular (carrot-shaped) neoplastic cells with FlexnerWintersteiner-type rosette formation. Mass location and histologic and ultrastructural features were suggestive of retinoblastomas. One ocular mass was composed of ribbons and rosettes of neoplastic cells with multiple areas of neuronal differentiation and was diagnosed as a teratoid medulloepithelioma. A cutaneous mass from an electric eel (Electrophorus electricus) consisted of rosettes and streams of elongate neoplastic cells. The epidermal electroreceptor (ampullary) organ was considered as an origin. Although distant metastases were not observed, neoplasms were generally locally aggressive with postexcision recurrence. There was occasional spread to or de novo occurrence within the contralateral eye.Keywords eye, fish, medulloepithelioma, primitive neuroepithelial neoplasms, retinoblastoma, skin A number of neoplastic disorders have been reported in fish. Some well-documented neoplasms include viral-induced dermal sarcomas in walleyes and aflatoxin-associated hepatocellular adenomas and carcinomas in rainbow trout as well as a variety of sporadic tumors in numerous species. 1,2,12 This report details spontaneous ocular and cutaneous tumors in multiple fresh and marine teleost species with features characteristic of neuronal embryonal tumors.Neuronal embryonal tumors arise from neuroectodermal progenitor cells within subependymal matrix layers and have morphology and aggressive behavior in common.10 Tumor types include medulloepitheliomas, neuroblastomas, retinoblastomas, ependymoblastomas, and primitive neuroectodermal tumors (PNETs). PNETs are derived from pluripotent germinal neuroepithelial cells and may be further classified on the basis of anatomic location as medulloblastomas, cerebral PNETs, or peripheral neuroectodermal tumors. Note that classification schemes may differ because the cell origin of these tumors is often not well understood.In humans, neuronal embryonal tumors often arise within the first decade of life. Chromosomal deletions and/or MYCN gene amplification have been noted in affected children and may play a role in pathogenesis in humans.3 Retinoblastomas predominantly occur following inactivation of both RB1 (retinoblastoma susceptibility protein) tumor suppressor gene alleles. 13 Materials and MethodsMedical records, archived tissues, and histologic sections were evaluated as collected between 2001 and 2009 from 11 adult fish of 11 different species (Table 1) and housed at one of two facilities. Tissues taken at necropsy consisted of whole or representative sections of all major organs, including skin or body wall and bone. Smaller fish were fixed whole in formalin and bisected along the median plane for histo...

Epizootic neoplasia in a managed population of Atlantic bumper fish, Chloroscombrus chrysurus (Osteichthyes: Carangidae), at a public aquarium

“…Medulloepitheliomas belong to a group of neoplasms known as embryonal tumours with multilayered rosettes (Kaliki et al, 2013;Korshunov et al, 2016). A few cases teratoid medulloepithelioma are reported in fish, including a tinfoil barb and a series of Japanese medaka exposed to methylazoxymethanol acetate (Hawkins et al, 1986;Kagan et al, 2010). Muñoz -Gutiérrez et al, 2018;Roth et al, 1987;Saunders et al, 1969;Uchida et al, 2003).…”

A Retrospective Study of the Prevalence and Classification of Intestinal Neoplasia in Zebrafish (Danio Rerio)

“…Zebrafish develop common spontaneous neoplasia associated with aging, including spermatocytic seminoma and ultimobranchial gland adenoma that occur in zebrafish at 1.5 to 2 years of age, 7,10 and embryonal neuroectodermal tumors of the central nervous system in both juvenile and adult fish. 5,27 Although many zebrafish tumors recapitulate their human counterparts in terms of basic histologic appearance, certain molecular characteristics (increased cell proliferation, nuclear atypia, and cellular differentiation) and mechanisms of regulation (cell cycle and apoptosis), 3,22,28 there is relatively little understanding of how conserved tumor antigens are between the two species. Some researchers developing zebrafish tumor models consider histologic evaluation as an unnecessary step, 29 which would lead to potentially erroneous conclusions because without it as a starting point, obvious tissue and cellular similarities cannot be determined.…”

Ocular glioneuroma with medulloepitheliomatous differentiation in a goldfish (Carassius auratus)

“…Barbodes subwanefeldi). 13 Among other primitive ocular neoplasms with an ectodermic origin, a primitive neuroectodermal tumor was reported in a telescope goldfish. 3 In veterinary medicine, there are no reports of glioneuroma to the authors' knowledge.…”