Spontaneous multicentric myxoma of the dermal nerve sheaths in farmed European eels Anguilla anguilla

Abstract

This report describes a peripheral nerve sheath tumour in 8 European eels Anguilla anguilla L. from a fish farm located in Croatia. The newborn tissue appeared as smooth and soft skin nodules without pronounced colour change. Nodules were dome-shaped with a pale crater and were present on different body areas. In general, nodules were located as series of differently sized protrusions extending along the lateral line on both sides of the fish, as well as sensory canals on the head. Cut sections showed a homogeneous, pale white-grey texture. Histologically, the pathological tissue was located in the dermis, occasionally intruding into the hypodermis, and pushing as a space-occupying mass against the underlying muscle tissue without any evident boundaries. The pressure also caused changes in the overlying epidermis, such as atrophy, spongiosis and erosion. In some areas, the epidermis was 1 cell thick and club and goblet cells had completely disappeared. Ultimately, these changes resulted in shallow ulceration. Tumour tissue was characterized by a scant population of spindle or stellate cells, with oval, hyperchromatic nuclei and pale cytoplasm embedded in a copious myxoid matrix. Cells were arranged in fascicles and whorls, extending in a poorly defined manner among the dermal collagen bundles. Occasionally, adipose cells were also detected, mainly in the central portion of the bulges. Myxoid areas appeared rich in metachromatic and alcianophilic mucous ground substance. Reticular fibres and collagenous connective tissue were scarce. Immunohistochemistry (IHC) using antibodies against S-100 and glial fibrillary acidic protein caused a slight positive reaction in neoplastic dendritic cells. High magnification showed the immunostaining to be cytoplasmic in all tumour cells. IHC with anti-calretinin antibody gave only negative results. Macroscopic, histological, histochemical and immunohistochemical findings were consistent with a diagnosis of multicentric myxoma of the dermal nerve sheaths, a tumour not yet reported in fish.

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

“…The identification of the exact histogenesis of these tumors is a matter of debate in medical literature and a hard challenge to face in daily diagnostic routines, both in mammals [ 1 , 42 , 43 , 44 , 59 ] and fishes [ 3 , 4 , 5 , 7 ]. Indeed, a similar histopathological presentation in piscine neoplasms has been referred to different histogeneses, such as sarcoma not otherwise specified [ 24 , 45 ], fibroma/fibrosarcoma [ 27 , 34 , 35 , 36 , 37 ], leiomyoma/leiomyosarcoma [ 38 , 39 , 60 ], rhabdomyoma/rhabdomyosarcoma [ 42 , 60 ], PWT [ 40 , 41 ], myxoma [ 37 ], chromatophoroma [ 23 , 26 , 27 , 33 ], and PNST [ 12 , 13 , 19 , 27 , 28 , 30 , 31 , 32 , 45 , 47 ]. In this context, histochemical and immunohistochemical stains might be helpful to define the histogenesis of a neoplasm, despite not always being successful [ 5 , 26 , 27 , 39 , 52 ].…”

“…Therefore, a large number of different spindle cell tumors have been reported in these animals, including peripheral nerve sheath tumors (PNSTs) [ 7 , 19 , 29 , 30 , 31 , 32 ], chromatophoromas [ 26 , 33 ], fibroma/fibrosarcoma [ 34 , 35 , 36 , 37 ], leiomyoma [ 38 , 39 ], myxoma [ 37 ], and perivascular wall tumors (PWTs) [ 40 , 41 ]. PNSTs can be further divided into benign PNST (BPNST) and malignant PNST (MPNST), with the former further categorized as Schwann cell tumor, neurofibroma, perineurioma [ 1 , 30 , 42 , 43 , 44 , 45 , 46 ], or myxoma of the dermal nerve sheaths [ 47 , 48 ]. Specifically, several PNST variants (i.e., classical schwannoma, neurofibroma, pigmented variants of both aforementioned and malignant schwannomas) have been reported in goldfish [ 19 , 30 , 31 , 32 ].…”

Immunohistochemical Study of Four Fish Tumors

“…), myxoma (Gjurčević et al. ), and chromatophoroma (particularly erythrophoroma; Ishikawa et al. ; Whipple et al.…”

Oral neoplasms in pickhandle barracuda Sphyraena jello from India

“…Myxomas are a rare tumour type in fishes. Cutaneous myxomas have been reported in Seriola lalandi (Keller et al 2011), Anguilla anguilla (Gjurcevic et al 2014), Arius jella (Singaravel et al 2016) and Carassius auratus (Shohrpoor et al 2016). We observed myxomatous lesions in pickhandle barracuda that were similar to those described by Keller et al (2011), who described bland spindle-shaped cells embedded in an abundant myxoid or mucoid extracellular matrix.…”