Excision and Subsequent Treatment of a Leiomyoma From the Periventiduct of a Koi (Cyprinus carpio koi)

PRIMARY HEPATIC NEOPLASIA IN THREE ADULT BAMBOO SHARKS (CHILOSCYLLIUM PLAGIOSUM AND CHILOSCYLLIUM PUNCTATUM) IN AN AQUARIUM POPULATION

Neoplasia in elasmobranchs is uncommonly documented. This report describes primary hepatic neoplasia in three adult female bamboo sharks under managed care: biliary adenocarcinoma in a whitespotted bamboo shark (Case 1; Chiloscyllium plagiosum), biliary adenocarcinoma in a brownbanded bamboo shark (Case 2; Chiloscyllium punctatum), and hepatocellular carcinoma in a whitespotted bamboo shark (Case 3). Case 1 presented with extensive cutaneous papillomas and was electively euthanized. At necropsy, a 4-cm-diameter, pale-tan, firm hepatic mass was identified and diagnosed histologically as a biliary adenocarcinoma. Case 2 presented with decreasing body condition despite normal food intake. Coelomic ultrasound and exploratory surgery revealed several large masses in both hepatic lobes, and the patient was euthanized. At necropsy, nine, 1-6-cm-diameter, black to tan, firm hepatic masses were identified and diagnosed histologically as biliary adenocarcinoma with branchial intravascular neoplastic emboli. Case 3 presented for routine health examination and was euthanized for diagnostic purposes after coelomic ultrasound revealed multiple hepatic masses. At necropsy, two 1-3-cm-diameter, brown- and-black mottled, firm hepatic masses were identified and diagnosed histologically as hepatocellular carcinoma. Immunohistochemistry was performed in two of these cases and was noncontributory, likely because of a lack of cross reactivity between antibodies (antipancytokeratin) and elasmobranch tissues.

Local and Regional Anesthesia in Zoological Companion Animal Practice

Local anesthetics provide analgesia and can be incorporated into multimodal anesthetic protocols. They work by blocking the voltage-dependent sodium ion channels along neurons that mediate nociception. Systemically, these drugs can be cardiotoxic in a dose-dependent manner. Lidocaine and bupivacaine are the most commonly used local anesthetics and their use has been reported in all classes of vertebrates. Despite anecdotal reports to the contrary, zoologic companion animals are unlikely to be more susceptible to the cardiotoxic effects of local anesthetics than domestic small animals. Local anesthetics can be clinically useful for analgesia and anesthesia in zoologic companion animal practice.

Peripheral Nerve Sheath Tumors Resembling Human Atypical Neurofibroma in Goldfish (Carassius auratus, Linnaeus, 1758)

Simple Summary

In animals, especially in fish, dermal neoplasms are a common finding. A distinction between peripheral nerve sheath tumors (PNSTs) and other spindle cell tumors (SCTs) is not always possible when relying exclusively on routine cytological and histopathological findings. The current study aims to determine a minimal subset of stains required to correctly identify PNSTs in goldfish and describes, in detail, six dermal nodules that resemble atypical neurofibroma in humans. Interestingly, muscular and fibroblastic tumors were excluded using Azan trichrome staining, while Alcian blue and Gomori’s reticulin stains revealed the presence of intratumoral areas of mucins and basement membrane fragments, respectively. In addition, PAS and PAS with diastase pretreatment confirmed the latter finding and revealed intra- and extracellular glycogen granules. Immunohistochemistry displayed reactivity for S100 protein, CNPase, and phosphorylated and non-phosphorylated neurofilament-positive axons. Altogether, these findings suggested that Azan trichrome staining, Gomori’s reticulin staining, and immunohistochemistry for S100 protein and CNPase represent a useful set of stains to identify and characterize PNSTs in goldfish.

Abstract

Skin spindle cell tumors (SSTs) frequently occur in fishes, with peripheral nerve sheath tumors (PNSTs) being the most commonly reported neoplasms in goldfish. However, distinguishing PNSTs from other SCTs is not always possible when relying exclusively on routine cytological and histopathological findings. Therefore, the aim of this study is to characterize six skin nodules, resembling atypical neurofibromas in humans, found in six cohabiting goldfish (Carassius auratus), and to determine a minimal subset of special stains required to correctly identify PNSTs in this species. Routine cytology and histopathology were indicative of an SCT with nuclear atypia in all cases, with randomly distributed areas of hypercellularity and loss of neurofibroma architecture. Muscular and fibroblastic tumors were excluded using Azan trichrome staining. Alcian blue and Gomori’s reticulin stains revealed the presence of intratumoral areas of glycosaminoglycans or mucins and basement membrane fragments, respectively. PAS and PAS–diastase stains confirmed the latter finding and revealed intra- and extracellular glycogen granules. Immunohistochemistry displayed multifocal, randomly distributed aggregates of neoplastic cells positive for S100 protein and CNPase, intermingled with phosphorylated and non-phosphorylated neurofilament-positive axons. Collectively, these findings are consistent with a PNST resembling atypical neurofibroma in humans, an entity not previously reported in goldfish, and suggest that Azan trichrome staining, reticulin staining, and immunohistochemistry for S100 protein and CNPase represent a useful set of special stains to identify and characterize PNSTs in this species.

Gastric leiomyoma in a sea bass Dicentrarchus labrax broodfish

This report describes a spontaneously arising non-infiltrative neoplasm of gastric tunica muscularis in a broodstock sea bass Dicentrarchus labrax from an Italian aquaculture farm. Microscopically, the mass was circumscribed and non-encapsulated and was composed of spindle cells arranged in parallel interlacing bundles or, occasionally, a whirling pattern. Cells had a small quantity of eosinophilic cytoplasm with distinct cell borders. Neoplastic cells were immuno-reactive with smooth muscle actin, vimentin and desmin; S100 was negative. The mucosal epithelium was intact with no neoplastic involvement. A gastric leiomyoma was diagnosed based on the findings. More efforts should be made to study the possible etiology of leiomyoma affecting fish from aquaculture.

Evidence-Based Advances in Aquatic Animal Medicine

Fish and aquatic invertebrates deserve evidence-based medicine. Pharmacologic information is available; most pharmacokinetic studies are derived from the aquaculture industry and extrapolated to ornamental fish. Conversely, advanced diagnostics and information regarding diseases affecting only ornamental fish and invertebrates require more peer-reviewed experimental studies; the examples of carp edema virus, sea star wasting disease, seahorse nutrition, and gas bubble disease of fish under human care are discussed. Antinociception is also a controversial topic of growing interest in aquatic animal medicine. This article summarizes information regarding new topics of interest in companion fish and invertebrates and highlights some future avenues for research.