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Peripheral nerve sheath tumors (PNSTs) include schwannomas, neurofibromas (NFs), and plexiform neurofibromas (PNFs), among others. While they are benign tumors, according to their biological behavior, some have the potential for malignant degeneration, mainly PNFs. The specific factors contributing to the more aggressive behavior of some PNSTs compared to others are not precisely known. Considering that lipid homeostasis plays a crucial role in fibrotic/inflammatory processes and in several cancers, we hypothesized that the lipid asset was also unbalanced in this group of nerve tumors. Through untargeted lipidomics, NFs presented a significant increase in ceramide, phosphatidylcholine, and Vitamin A ester. PNFs displayed a marked decrease in 34 out of 50 lipid class analyzed. An increased level of ether- and oxidized-triacylglycerols was observed; phosphatidylcholines were reduced. After sphingolipidomic analysis, we observed six sphingolipid classes. Ceramide and dihydroceramides were statistically increased in NFs. All the glycosylated species appeared reduced in NFs, but increased in PNFs. Our findings suggested that different subtypes of PNSTs presented a specific modulation in the lipidic profile. The untargeted and targeted lipidomic approaches, which were not applied until now, contribute to better clarifying bioactive lipid roles in PNS natural history to highlight disease molecular features and pathogenesis.

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.

An adult Goldfish (Carassius auratus) developed an exophitic, multinodular, mass in the dorsal region involving the fin. The clinical and pathologic approach included ultrasonography, cytology, histopathology, immunohistochemistry, and ultrastructural evaluation. B-mode and color Doppler ultrasonographic findings showed an oval, well-defined mass with slightly inhomogeneous parenchymatous echotexture associated with an intense intralesional vascularization. Cytology and histology revealed neoplastic pleomorphic spindle cells arranged in a storiform pattern or in palisades typical of Antoni A pattern schwannoma. Moderate anisocytosis and anisokaryosis and occasional binucleation were also present. The neoplastic tissue deeply infiltrated the skeletal muscle of the dorsal region. Immunohistochemistry showed a diffuse cytoplasmic immunoreactivity of neoplastic cells to S100 protein and proliferating cell nuclear antigen (PCNA); glial fibrillary acidic protein was negative. The PCNA proliferation rate was 23.5% (calculated as the mean of 10 fields). Ultrastructurally, neoplastic cells were juxtaposed with parallel nuclei forming the typical palisade pattern and sharing cytoplasmic and nuclear features with human schwannoma. This is the first cytologic description supplied with echographic investigation of a malignant schwannoma in a fish species.

A domestic ferret was submitted for sterilisation because of right testis enlargement. Oestradiol and cortisol concentrations were within normal physiological ranges, but testosterone was below and progesterone above normal. Microscopically, the right testis, with the exception of a small part of the epididymis, was replaced with neoplastic tissue. The tumour was composed of streams and bundles of closely packed spindle to ovoid cells forming whorls around collagen and capillaries, and separated by a collagenous matrix. In some areas, cells were loosely arranged and separated by a pale myxomatous matrix. The left testis showed atrophy. The majority of neoplastic cells expressed vimentin and S-100 protein, while expression of collagen IV was moderate and there was no expression of glial fibrillary acid protein. On the basis of macroscopical and histopathological findings, and supported by immunohistochemical reactivity, the diagnosis of benign peripheral nerve sheath tumour was made. This is the first report of benign peripheral nerve sheath tumour in ferret testis.

Background and methods: 44 peripheral nerve sheath tumors (PNST) (27 schwannomas, 9 neurofibromas and 8 malignant peripheral nerve sheath tumors (MPNST)) were analyzed to determine DNA ploidy pattern and to clarify the conflicting data in the literature concerning this topic (whether benign PNSTs are aneuploid or not). For further insight we analyzed 6 schwannomas, one atypical neurofibroma and five MPNSTs by fluorescence in situ hybridization (FISH) technique using centromeric chromosome probes (7, 17 and 18) and automatic image analysis station, Metafer 4. Results: Benign schwannomas (including the problematic variants as ancient, cellular, neuroblastoma like and multiplex schwannomas) could be characterized by euploid‐polyploidisation and by their 4c peak height value which was usually more than 10% of total cell number measured. These characters were not found among neurofibromas and MPNST‐s. FISH analysis revealed and confirmed that the ‘normal’ euploid–polyploid cells are mainly eusomic–polysomic containing two, four, eight or sixteen signals for each chromosomes examined, but in a small proportion aneusomy was found among tumor cells of benign schwannomas (average: 2.58; range 1.33–3.44). In contrast, the atypical neurofibroma displayed marked aneusomy (18.44%) but it contained normal eusomic and polysomic cells too. Two diploid MPNSTs proved to be clearly aneusomic with trisomy of chromosome 17 and monosomy of chromosome 18. Conclusions: All these data suggest that ploidy pattern determination combined with FISH analysis may be a very useful supplementary tool for making a right diagnosis (to differentiate benign versus malignant schwannomas in problematic variants) and to understand better the malignant transformation in PNSTs.