Spontaneous neoplasms in harbour porpoises Phocoena phocoena.

Harbour porpoises are widely distributed in the North Atlantic and represent the most abundant cetacean species in the North and Baltic Seas. Spontaneous neoplasms are relatively rarely reported in cetaceans, and only little is known about neoplasia in harbour porpoises. Thus, archival material was reviewed for spontaneous neoplasms in harbour porpoises recorded during post-mortem examinations between 1999 and 2018. Neoplasms were identified in 7 adult porpoises: 6 animals originating from the North and Baltic Seas and investigated as part of German and Dutch systematic health monitoring programs, and 1 porpoise from Greenlandic waters. The tumours were of different histogenetic origins and further characterised by histology and immunohistochemistry. One individual had a neoplasia in the digestive tract (adenocarcinoma, n = 1); 4 animals, in the genital tract (Sertoli cell tumour, n = 1; genital leiomyoma/fibroleiomyoma, n = 3); and 2 porpoises, in endocrine organs (adrenal adenoma, n = 2). This is the first report of an adenocarcinoma in the liver, a testicular Sertoli cell tumour and adrenocortical adenomas in harbour porpoises. The cause of the tumorigenesis in examined cases remains undetermined. The involvement of endogenous factors, including mutation of cell cycle regulating genes, such as the tumour-suppressor gene p53, cannot be ruled out. The aetiopathogenetic significance of exogenous factors, such as infectious agents like liver flukes or anthropogenic factors, including persistent organic pollutants, should be the subject of future investigations.

[Buiatrics: What's your diagnosis?] / Rindermedizin ­ Was ist Ihre Diagnose?

INTRODUCTION: Therapy of a high-grade balanoposthitis with partial penile and preputial prolapse after unsuccessful initial therapy of a ten-year-old dexter bull. Two punctures, about 1 cm depth were found at the base of the prolapsed tissue, which were probably caused by partially perforating U-stitches by the local veterinarian. The highly inflamed and swollen tissue disabled the penis to retract. The prolapse was repositioned and the preputial opening was partially closed using a modified Buhner stitch. Consecutively, antibiotics and anti-inflammatory drugs were administered, and regular wound toilets were performed. After 14 days, the increase in circumference at the base of the prolapse was partially removed and histopathologically identified as pyogranulomatous inflammation. Surgery was repeated two weeks later. Potentia coeundi could thus be re-established. This case shows that regular breeding hygienic examinations are of great importance in order to identify morphological changes in early stages and to treat them adequately.

INTRODUCTION: Traitement d'une importante balanoposthite avec prolapsus pénien et préputial partiel après traitement initial infructueux d'un taureau Dexter de dix ans. Deux perforations d'environ 1 cm de profondeur ont été trouvées à la base du tissu prolabé, probablement causées par des points de suture en U posés par le vétérinaire traitant pour éviter une récidive. Le tissu très enflammé et enflé a empêché le pénis de se rétracter. Le prolapsus a été repositionné et l'ouverture préputiale a été partiellement fermée à l'aide d'un point de Buhner modifié. Consécutivement, des antibiotiques et des anti-inflammatoires ont été administrés et des toilettes des plaies régulières ont été effectuées. Après 14 jours, l'augmentation de la circonférence à la base du prolapsus a été partiellement réséquée et identifiée histopathologiquement comme une inflammation pyogranulomateuse. La chirurgie a été répétée deux semaines plus tard. La potentia coeundi a pu ainsi être rétablie. Ce cas montre que des examens d'hygiène d'élevage réguliers sont d'une grande importance afin d'identifier les changements morphologiques aux stades précoces et de les traiter de manière adéquate.

Aspects of transition cow metabolomics-Part II: Histomorphologic changes in the liver parenchyma throughout the transition period, in cows with different liver metabotypes and effects of a metaphylactic butaphosphan and cyanocobalamin treatment.

The aims of this study were to evaluate histopathologic changes during the transition period, describe the histopathological features of the metabotypes identified in Part I (Schären et al., 2021b), and investigate effects of a metaphylactic treatment with butaphosphan and cyanocobalamin (BCC) on the liver parenchyma. Eighty German Holstein cows (mean 305-d production: 10,957 kg, range: 6,480-15,193 kg; mean lactation number: 3.9, range: 2-9) from a commercial dairy farm in Saxony, Germany, were enrolled in a randomized, prospective, triple-blinded study. Two groups received a treatment with BCC (5 or 10 mL/100 kg of body weight 10% butaphosphan and 0.005% cyanocobalamin, Catosal, Bayer Animal Health, n = 20 each) and one group a placebo treatment (NaCl 0.9%, n = 40). Liver biopsy specimens were collected 14 d antepartum (AP) and 7, 28, and 42 d postpartum (PP), routinely processed for histologic examination, and stained with hematoxylin and eosin, Sudan III, periodic acid-Schiff, and picrosirius red stains. The sections were assessed for fat and glycogen content and degenerative, inflammatory, fibrotic, and proliferative changes. The statistical analysis included the effects of the sampling day, the lactation number, the treatment, and the metabotype (A = medium, B = minor, C = large alterations in the liver metabolome profile between AP and PP status). There was mild to moderate fat infiltration in the liver of 37% of cows in the last 2 wk AP, and moderate to severe fat infiltration in 66% of cows in the first days PP. The degree of fat infiltration increased from 2 wk AP until the end of the first week PP, and then decreased until the end of the study period, at which time about 25% of cows had moderate to severe fatty infiltration. Lipidosis was positively correlated with the severity of liver cell degeneration, and negatively correlated with the degree of glycogen deposits. Complete glycogen depletion of hepatocytes was not observed in cows, even in the presence of severe hepatic lipidosis. Moderate to severe lymphocytic hepatitis was seen in 39% of cows throughout the study period, and cows with lactation numbers 5 or greater had perisinusoidal fibrosis more often than younger cows. Severe fibrosis and cirrhosis of the liver did not occur. Metabotype B animals exhibited a higher chance of fatty infiltration, lower glycogen storage, and perisinusoidal fibrosis and for this metabotype positive correlations were calculated between increased fat deposition in the liver and marked glycogen depletion, and increased degenerative, inflammatory, fibrotic, and proliferative changes of hepatic tissue. For the treatment with BCC, no significant effect was observed. In summary, during the transition period, the liver of dairy cows is characterized by fat accumulation and glycogen depletion and histologic signs of hepatitis and hepatocyte degeneration. These histomorphologic changes were accentuated in animals exhibiting little alterations in their liver metabolome profile across the transition period (metabotype B) and support the assumption of a decreased grass silage quality as a causative factor.

Complex segregation analysis of familial amyloidosis in Oriental shorthair cats.

Amyloidosis in Siamese/Oriental cats is a lethal condition with variable age of clinical onset. There is no sex predisposition and clinical signs of disease usually become apparent by 1-7 years of age. In the terminal stages, the liver is enlarged and pale, and contains parenchymal hemorrhages. In the present study, pedigree data from 17 cats with clinical signs consistent with amyloidosis underwent genetic analysis. Necropsy and histopathological data were available for 10 of the 17 cats. Necropsy findings included pale, fragile and enlarged livers with capsular ruptures and parenchymal hemorrhages, and sanguineous effusions in the abdominal cavity. Congo red staining with birefringence confirmed systemic amyloidosis mostly involving the liver and thyroid gland. In four of the 10 cases, protein deposits were classified as amyloid A protein (AA-amyloid) by immunostaining. Pedigree data for all 17 affected cats indicated a familial trait. Animal threshold model analysis demonstrated that the heritability for amyloidosis was 0.56 ± 0.09 (standard error). Complex segregation analysis was used for statistical comparisons among models to determine environmental or sex dependent effects, and Mendelian, polygenic, or mixed Mendelian and polygenic inheritance patterns. A mixed model with a Mendelian and polygenic component provided the best fit to the data and thus was most likely. All other models of inheritance were rejected due to their insufficient ability to explain segregation of amyloidosis. In conclusion, we found evidence for a complex genetic basis for amyloidosis in Oriental shorthair cats.

Long-term radiographic and histological follow-up after resection of the distal interphalangeal joint using a plantar approach in German Holstein cows.

Resection of the distal interphalangeal joint (DIJ) is a claw-preserving method for treatment of septic arthritis. This study presents the radiographic and histological findings of the surgically-treated area after resection of the DIJ using a plantar approach in seven German Holstein cows. Histological postmortem evaluation 439 to 710 days after surgery showed that there was extensive proliferation of connective tissue rich in collagen fibres in the space left after resection in three cows; this was classified as fibrous ankylosis. In the remaining four cows, histological evaluation 1010 to 1756 days after surgery showed extensive new bone formation in the joint cavity consistent with osseous ankylosis. Radiographs of the resected DIJ region obtained at the time of histological examination revealed no osseous ankylosis in two cows, partial ankylosis in one cow and complete osseous ankylosis in four cows. Formation of complete osseous ankylosis after resection of the DIJ did take longer than 1-2 years in three of our specimens indicating a longer time span compared to earlier studies.

Predominance of Granular Cell Tumours among Testicular Tumours of Rabbits (Oryctolagus cuniculi f. dom.).

Testicular neoplasms are reported rarely in pet and laboratory rabbits (Oryctolagus cuniculi f. dom.), with interstitial cell tumours being the most commonly described testicular neoplasm. In this retrospective study, paraffin wax-embedded testicles with neoplastic changes from 52 rabbits were investigated. Five out of 52 animals exhibited more than one tumour type, resulting in a total of 57 tumours. Granular cell tumours were the most prevalent neoplasm with 36 examples (63%) out of the 57 testicular tumours. Interstitial cell tumours, Sertoli cell tumours and seminomas occurred less frequently. Granular cell tumours of the testis are rare in rabbits. Histological similarities between granular cell and interstitial cell (Leydig cell) tumours in haematoxylin and eosin-stained tissue sections may lead to misdiagnoses. The periodic acid-Schiff reaction or immunohistochemistry for periaxin and S100 protein, as well as ultrastructural analysis, are useful methods to confirm the diagnosis.

Expression of Neuroectodermal Markers in Atypical Fibromas in Two Dwarf Hamsters (Phodopus spp.).

A 2-year-old male Djungarian hamster (Phodopus sungorus) and a 1-year-old male Roborovski hamster (Phodopus roborovskii) were presented with expansile subcutaneous masses. The well-demarcated, firm, grey, multilobulated nodules displayed an homogeneous, white-grey cut surface. Histological examination revealed a neoplasm of variable cellularity consisting of spindle-shaped to polygonal 'ganglion cell-like' cells with abundant, amphophilic, vacuolated cytoplasm. Immunohistochemically, the tumour cells were labelled intensely for vimentin and nestin, moderately for neuron specific enolase and weakly for melan-A. The histological and immunohistochemical findings were suggestive of an atypical fibroma with evidence of a neuroectodermal phenotype.

Cutaneous Pigmented Neurofibroma in a Pig - Morphology and Immunohistochemical Profile.

Peripheral nerve sheath tumours are rare in pigs. In the present case, a juvenile female hybrid pig showed a solitary, pigmented, cutaneous mass. Histologically, it consisted of clustered melanin-laden, epithelioid cells as well as spindle cells forming bundles and nodules. The latter were surrounded by perineurial-like cells. Single Wagner-Meissner-like corpuscles were present. Immunohistochemically, the epithelioid cells expressed S100 protein, melan A and the p75 neurotrophin receptor (p75NTR). The spindle cells expressed S100, sex determining region Y-box 2, p75NTR, Krox20, growth associated protein 43 and glial fibrillary acidic protein. Perineurial-like cells were positive for p75NTR, α-smooth muscle actin and cytokeratin. Taken together, the histological und immunohistochemical findings support the diagnosis of a cutaneous pigmented neurofibroma.

Atypical Cowpox Virus Infection in a Series of Cats.

Within 4 weeks, five cats with skin lesions affecting the hindlimbs and mainly consisting of oedema, hyperaemia and plaque-like alterations were presented to the same veterinary clinic. The cats were suffering from lameness, trauma, renal insufficiency or complicated tail amputation. Although the lesions seemed unusual for a poxvirus infection, microscopical examination of biopsy samples or specimens taken during necropsy examination revealed ballooning degeneration of keratinocytes with eosinophilic, cytoplasmic inclusion bodies indicative of an orthopoxvirus infection. Cowpox virus infection was verified using immunohistochemistry and virus isolation. Molecular analysis revealed identical haemagglutinin gene sequences in four cases and spatiotemporal circumstances in some cases pointed to hospital-acquired transmission. Unusual manifestations of feline cowpox may have an unexpected risk for human infection.

Investigation into diseases in free-ranging ring-necked pheasants (Phasianus colchicus) in northwestern Germany during population decline with special reference to infectious pathogens.

The population of ring-necked pheasants (Phasianus colchicus) is decreasing all over Germany since the years 2008/2009. Besides impacts of habitat changes caused by current rates of land conversion, climatic influences or predators, a contribution of infectious pathogens needs also to be considered. Infectious and non-infectious diseases in free-living populations of ring-necked pheasants have been scarcely investigated so far. In the present study, carcasses of 258 deceased free-ranging pheasants of different age groups, predominantly adult pheasants, collected over a period of 4 years in the states of Lower Saxony, North Rhine-Westphalia and Schleswig-Holstein, were examined pathomorphologically, parasitologically, virologically and bacteriologically, with a focus set on infectious pathogens. A periocular and perinasal dermatitis of unknown origin was present in 62.3% of the pheasants. Additional alterations included protozoal cysts in the skeletal musculature (19.0%), hepatitis (21.7%), enteritis (18.7%), gastritis (12.6%), and pneumonia (11.7%). In single cases, neoplasms (2.6%) and mycobacteriosis (1.7%) occurred. Further findings included identification of coronaviral DNA from trachea or caecal tonsils (16.8%), siadenoviral DNA (7.6%), avian metapneumoviral RNA (6.6%), and infectious bursal disease viral RNA (3.7%). Polymerase chain reaction (PCR) on herpesvirus, avian influenza virus (AIV), paramyxovirus type 1 (PMV-1), avian encephalomyelitis virus (AEV), and chlamydia were negative. Based on the present results, there is no indication of a specific pathogen as a sole cause for population decline in adult pheasants. However, an infectious disease can still not be completely excluded as it may only affect reproduction effectivity or a certain age group of pheasants (e.g., chicks) which were not presented in the study.

Canine Central Nervous System Neoplasm Phenotyping Using Tissue Microarray Technique.

Tissue microarrays (TMAs) represent a useful technique for the simultaneous phenotyping of large sample numbers and are particularly suitable for histopathologic tumor research. In this study, TMAs were used to evaluate semiquantitatively the expression of multiple antigens in various canine central nervous system (CNS) neoplasms and to identify markers with potential discriminative diagnostic relevance. Ninety-seven canine CNS neoplasms, previously diagnosed on hematoxylin and eosin sections according to the World Health Organization classification, were investigated on TMAs, with each tumor consisting of 2 cylindrical samples from the center and the periphery of the neoplasm. Tumor cells were phenotyped using a panel of 28 monoclonal and polyclonal antibodies, and hierarchical clustering analysis was applied to group neoplasms according to similarities in their expression profiles. Hierarchical clustering generally grouped cases with similar histologic diagnoses; however, gliomas especially exhibited a considerable heterogeneity in their positivity scores. Multiple tumor groups, such as astrocytomas and oligodendrogliomas, significantly differed in the proportion of positive immunoreaction for certain markers such as p75NTR, AQP4, GFAP, and S100 protein. The study highlights AQP4 and p75NTR as novel markers, helping to discriminate between canine astrocytoma and oligodendroglioma. Furthermore, the results suggest that p75NTR and proteolipid protein may represent useful markers, whose expression inversely correlates with malignant transformation in canine astrocytomas and oligodendrogliomas, respectively. Tissue microarray was demonstrated to be a useful and time-saving tool for the simultaneous immunohistochemical characterization of multiple canine CNS neoplasms. The present study provides a detailed overview of the expression patterns of different types of canine CNS neoplasms.

Malignant Glomus Tumour (Glomangiosarcoma) with Additional Neuroendocrine Differentiation in a Horse.

A 13-year-old Icelandic crossbred horse was presented with headshaking and progressive impairment of chewing. A slowly growing mass was identified in the anterior maxilla. This was associated with lysis of the alveolar bone and the roots of the incisors and there were nodular proliferations affecting the nasal septum and conchae. There was no response to chemotherapy and so the horse was humanely destroyed. Based on morphological, immunohistochemical and ultrastructural findings the mass was classified as a malignant glomus tumour with multifocal vascular spaces and additional neuroendocrine differentiation. An oronasal glomus tumour with neuroendocrine differentiation has not been described previously in an animal.

[Subcutaneous Taenia crassiceps-cysticercosis in a dog with Cushing's syndrome]. / Subkutane Taenia-crassiceps-Zystizerkose bei einem Hund mit Cushing-Syndrom.

A male, 12-year-old Cairn terrier suffering from Cushing's syndrome with two therapy-resistant inflammatory subcutaneous lesions was examined pathomorphologically and parasitologically. Within the subcutaneous tissue, there was a suppurative to necrotizing and histiocytic inflammation present with the formation of caverns. Intralesional whitish-grey cysts with a diameter of 1-4 mm were detected. Molecular investigations of the cysts confirmed the preliminary morphological identification as Cysticercus longicollis. The adenohypophysis showed an infiltrative growing carcinoma. Cysticercus longicollis is the metacestode of Taenia (T.) crassiceps, a tapeworm of foxes and coyotes. Small rodents are typical intermediate hosts, in which the metacestode develops within the body cavities as well as in the subcutis. Subcutaneous cysticercosis after infection with eggs of T. crassiceps is also described in different domestic animal species and in humans, who represent aberrant intermediate hosts. Immunosuppression due to Cushing's syndrome, probably caused by the tumor of the adenohypophysis, may have played a role in the pathogenesis of the present case.

Fatal Disseminated Toxoplasma gondii Infection in a Captive Harbour Porpoise (Phocoena phocoena).

A 7-year-old female harbour porpoise (Phocoena phocoena), born and held in captivity, suffered from reduced consciousness, imprecise and circling swimming movements and long phases of immobility over a period of 3 weeks. The animal died during treatment in a Danish open sea facility. Pathological examination revealed multifocal pyogranulomatous to necrotizing meningoencephalomyelitis, ganglioneuritis, plexus chorioiditis, myocarditis, hepatitis and adrenalitis with few intralesional protozoal tachyzoites and bradyzoites within cysts. Immunohistochemistry was positive for Toxoplasma gondii antigen within the lesions. Using polymerase chain reaction (PCR), the presence of T. gondii-specific genome fragments was confirmed. A multilocus PCR-restriction fragment length polymorphism analysis using nine unlinked marker regions (nSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico) resulted in the identification of T. gondii type II (variant Apico Type I), which is the T. gondii genotype dominating in Germany. This is the first description of disseminated fatal toxoplasmosis in a captive harbour porpoise that lived in an open sea basin. Surface water contaminated with toxoplasma oocysts is regarded as the most likely source of infection.

Malignant catarrhal fever in a Vietnamese pot-bellied pig. A potential threat to pigs in mixed-species exhibits?

Malignant catarrhal fever (MCF) represents a sporadic and often fatal disease in various ungulate species including rarely swine. A close contact between susceptible and reservoir species of ovine herpesvirus-2 (OvHV-2) is a requirement for virus transmission. As in ruminants, a rapid course of disease with lymphohistiocytic meningoencephalitis and necrotizing vasculitis in multiple organs is frequently seen in porcine MCF. This report describes a case of MCF in a Vietnamese pot-bellied pig, which was kept in a zoological exhibit with direct contact to various ruminants. It represents the first description of porcine MCF with proven natural OvHV-2 infection in Germany. OvHV-2 should be considered as cause of fatalities among swine especially in mixed-species exhibits as present in many zoological gardens. Also farm pigs kept in free ranging husbandry systems with potential contact to sheep and other ruminant species may be at risk.

Polycystic kidneys and GM2 gangliosidosis-like disease in neonatal springboks (Antidorcas marsupialis).

Clinical, gross, histopathologic, electron microscopic findings and enzymatic analysis of 4 captive, juvenile springboks (Antidorcas marsupialis) showing both polycystic kidneys and a storage disease are described. Springbok offspring (4 of 34; 12%) were affected by either one or both disorders in a German zoo within a period of 5 years (2008-2013). Macroscopic findings included bilaterally severely enlarged kidneys displaying numerous cysts in 4 animals and superior brachygnathism in 2 animals. Histopathologically, kidneys of 4 animals displayed cystic dilation of the renal tubules. In addition, abundant cytoplasmic vacuoles with a diameter ranging from 2 to 10 µm in neurons of the central and peripheral nervous system, hepatocytes, thyroid follicular epithelial cells, pancreatic islets of Langerhans and renal tubular cells were found in 2 springbok neonates indicative of an additional storage disease. Ultrastructurally, round electron-lucent vacuoles, up to 4 µm in diameter, were present in neurons. Enzymatic analysis of liver and kidney tissue of 1 affected springbok revealed a reduced activity of total hexosaminidase (Hex) with relatively increased HexA activity at the same level of total Hex, suggesting a hexosaminidase defect. Pedigree analysis suggested a monogenic autosomal recessive inheritance for both diseases. In summary, related springboks showed 2 different changes resembling both polycystic kidney and a GM2 gangliosidosis similar to the human Sandhoff disease. Whether the simultaneous occurrence of these 2 entities represents an incidental finding or has a genetic link needs to be investigated in future studies.

[Peripheral keratinizing ameloblastoma in a dwarf rabbit (Oryctolagus cuniculus f. dom.)]. / Peripheres keratinisierendes Ameloblastom bei einem Zwergkaninchen (Oryctolagus cuniculus f. dom.).

A 3.5-year-old, male, neutered dwarf rabbit was presented with a history of a fast-growing gingival mass at the maxilla. The neoplasm was surgically completely excised. Histopathologically, an expansively growing, multilobulated, partially cystic, peripheral, keratinizing ameloblastoma was diagnosed. The immunohistochemical phenotyping of the tumour cells resulted in cytoplasmic labelling with various pan-cytokeratin antibodies. The cytokeratins 5/6, 7, 10 and 14 were expressed variably. Cytokeratin 20 was not detected. Vimentin was expressed in the cytoplasm of mesenchymal cells of the tumour stroma. In addition, in the nuclei of approximately 10% of the tumour cells the protein of the tumour suppressor gene p53 was expressed while in approximately 5% the proliferation marker Ki67 was expressed. Odontogenic tumours should be considered as a differential diagnosis of oral masses in rabbits.

Feline coccygeal teratoma: immunohistochemical characterization of immature tissue components.

Congenital teratomas arising in the coccygeal region have not been reported in domestic animals. This report describes a congenital coccygeal teratoma in a male Burmese cat. A round to oval expansile mass with solid and cystic areas was found ventral to the 5th to 7th caudal vertebrae. Microscopically, the tumour was composed of derivatives of all three primordial germ layers with neuroectodermal predominance. Immunohistochemical double labelling identified immature tissue components in combination with Sox2, a regulator of stem cell proliferation and differentiation. Few Sox2-positive cells co-expressed the neural crest stem cell markers vimentin and neurotrophin receptor p75(NTR). Not all Sox2- and p75(NTR)-positive cells expressed vimentin. An overlapping expression of vimentin-negative and Sox2-, p75(NTR)-positive cells and GFAP- and p75(NTR)-positive cells may indicate a transition stage from immature to mature non-myelinating Schwann cells. Periaxin-positive myelinating Schwann cells surrounding neurofilament-positive axons were observed. Sox2 was additionally expressed in immature odontogenic epithelial cells and in immature cells of endodermal origin. Sox2 was not observed in mature cells, with the exception of satellite glial cells and mucous glands. Despite the presence of immature tissue components, no recurrence was observed 1 year after surgical removal.

[Congenital embryonal rhabdomyosarcoma of the head in a red and white German Holstein calf]. / Kongenitales embryonales Rhabdomyosarkom am Kopf eines rotbunten Deutsche-Holstein-Kalbes.

Tumours with skeletal-muscle differentiation are rare in companion animals. They are differentiated into benign rhabdomyomas and malignant rhabdomyosarcomas. A female German Holstein calf displayed a congenital, spherical, subcutaneous mass at the lateral side of the head. Histology revealed an encapsulated, expansile, highly cellular mass consisting of a reticular meshwork of moderately pleomorphic, small spindle-shaped to round cells within a fibrovascular to myxoid stroma as well as multifocal, large, blunt, multinucleated myotube-like cells (strap cells). Electron microscopy demonstrated characteristic cytoplasmic bundles of myofilaments and Z-stripes within the strap cells. Immunoreactivity for vimentin was observed in the small spindle-shaped cells and for desmin in the strap cells. The results are consistent with the spectrum of findings characteristic for a bovine congenital embryonal rhabdomyosarcoma.

Primary intraparotid peripheral nerve sheath tumour with characteristics of benign schwannoma in a horse.

Schwannomas arising in the parotid gland are rare in man and are not documented in domestic animals. This report describes the clinical, morphological and immunohistochemical findings of a benign schwannoma in the parotid gland of a 12-year-old warmblood gelding. A slow-growing mass was surgically excised from the parotid gland and did not recur within the following 6 months. The tumour was well circumscribed and was composed of densely packed spindle cells partly arranged in an Antoni A pattern and intermixed with hypocellular areas resembling the Antoni B pattern. Tumour cells expressed vimentin, S100 protein, glial fibrillary acidic protein and variably neuron-specific enolase. Less than 5% of the neoplastic cells were immunolabelled with the proliferation marker Ki67. Although malignant melanomas frequently involve the parotid gland in horses, schwannomas should be included in the differential diagnosis of parotid masses.