Abstract
Simple SummaryIn 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.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.
Highlights
Neoplastic diseases are not exclusive to domesticated mammals [1] but are frequently reported to affect small mammal pets [2], reptiles [3], and fishes [3,4,5,6,7].Fish breeding is a constantly expanding business, carried out with seafood production, research, exhibition, and ornamental purposes
The current study describes, in detail, goldfish peripheral nerve sheath tumors (PNSTs) resembling atypical neurofibroma in humans, providing the scientific community with a description that might be helpful to veterinary pathologists and clinicians facing similar or identical tumors
The current study reports the in-depth characterization of six skin nodules in a group of six cohabiting goldfish, which led to a final diagnosis of neurofibroma, resembling the entity known as “atypical neurofibroma” in humans
Summary
Fish breeding is a constantly expanding business, carried out with seafood production, research, exhibition, and ornamental purposes. Fish are commonly used as laboratory animals, representing an important animal model for toxicological research [9] as well as for carcinogenesis and cancer development studies [10,11,12,13]. An economically promising niche is represented by exhibition fish breeding, with valuable animals reaching remarkable prices among hobbyists [14]. Spontaneous neoplasms have been reported in fishes bred in aquaculture, in laboratory facilities, and in public and private aquaria, as well as in piscine wildlife [3,4,5,7,15,16,17,18]
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