Rare neural crest tumor in teleost species: olfactory neuroblastoma in a spotted pike-characin Boulengerella maculata

Abstract

One spotted pike-characin Boulengerella maculata, managed in a public display aquarium for 7 yr, developed a small unilateral pink growth associated with the right nare. The growth eventually extended through both nares after 5 mo. B. maculata is a species of piscivorous fish that relies on visual acuity when hunting prey. The rapidly-growing bilateral tumor would have impeded vision if left untreated. The fish was managed for over 10 mo using only surgical debulking, topical liquid nitrogen, and occasional nonsteroidal anti-inflammatory medications as needed to reduce tumor size and restore sight. Diagnosis proved challenging due to superimposed inflammation, neoplasm cellular inconsistencies, and a lack of proven immunohistochemical stains or other diagnostic stains. Using tumor location and appearance, histopathology, advanced imaging, electron microscopy, special staining, and immunohistochemistry, the ultimate diagnosis confirmed olfactory neuroblastoma, or esthesioneuroblastoma. Although long-term prognosis is poor, hunting strategy of the affected species may dictate quality of life, as appetite, body condition, and behavior remained largely unchanged in this animal until time of euthanasia.

Review of neoplasia in fish at a large display aquarium, 2005–2021

“…Neuronal embryonal tumors are relatively well documented in teleost fish. 12,16,23,47,49 In our study population, all of these tumors occurred in tropical freshwater fish. Most fish had nasal or ocular lesions, which is consistent with the current teleost literature.…”

“…Specific neoplasms reported in fish include squamous cell carcinoma, 13,24,31,39,42,51 infiltrative tubular carcinoma, 40 adenocarcinoma, 25 exocrine pancreatic carcinoma, 25 intestinal carcinoma, 25 soft-tissue sarcoma, 36,47 hemangiosarcoma, 20,47 rhabdomyosarcoma, 25,47 lepidosarcoma, 47 fibrosarcoma, 47 neu-ronal embryonal tumors, 23,46 lymphoma, 3,5,10,11,18,19,25,26,45,47,48 malignant ovarian germ cell tumor, 21,22,28 malignant nerve sheath tumor, 2,47 melanoma, 35,46 and a variety of benign tumors. 12,16,30,32,38,44,46,47,50 There are well-documented causes for fish neoplasia, such as a retrovirus causing walleye dermal sarcoma. 36,41 However, the causes of most fish neoplasms are unknown.…”