Cutaneous plexiform schwannoma in a pig

Cutaneous spindle cell tumors with features of peripheral nerve sheath tumors and concurrent cardiac involvement: neurofibromatosis type 1-like presentation in a Labrador Retriever dog

An 8-y-old intact male Labrador Retriever dog developed cutaneous masses over the entire body. On histologic evaluation, the masses were composed of bundles of fusiform neoplastic cells arranged around adnexa, with mild atypia and no mitoses, consistent with peripheral nerve sheath tumors (PNSTs). Immunohistochemically, neoplastic cells were immunoreactive for vimentin, glial fibrillary acidic protein (GFAP), and S100, confirming their perineurial origin. The dog was euthanized because of deteriorating clinical signs. In addition to the cutaneous masses, a cardiac mass was identified at postmortem examination. The histopathologic and immunohistochemical features of the cardiac mass were similar to those of the cutaneous masses. To our knowledge, the combination of multiple cutaneous masses with features of PNSTs and a concurrent cardiac lesion has not been reported previously in a dog. We suggest "neurofibromatosis type 1-like" presentation for this unique combination of cutaneous and cardiac masses. Further studies are required to investigate the etiopathogenesis of this condition and explore its genetic background.

Neoplastic lesions in domestic pigs detected at slaughter: literature review and a 20-year review (1998-2018) of carcass inspection in Catalonia

Background

The present paper reviews the occurrence of neoplasms in swine and presents a case series of 56 tumors submitted to the Slaughterhouse Support Network (Servei de Suport a Escorxadors [SESC] IRTA-CReSA]) from slaughtered pigs from 1998 to 2018 (April) in Catalonia (Spain). The aim of the study was to describe the spectrum of spontaneous neoplastic lesions found in slaughtered pigs and to compare the reported tumor cases with previous published data. Lymphoid neoplasms were characterized and classified using the WHO classification adapted for animals.

Results

The most reported neoplasm during this period was lymphoma (28). Within lymphomas, the B-cell type was the most common, being the diffuse large B-cell lymphoma (15/28) the most represented subtype. Other submitted non-lymphoid neoplasms included melanoma (7), nephroblastoma (3), mast cell tumor (2), liposarcoma (2), osteochondromatosis (2), papillary cystadenocarcinoma (1), peripheral nerve sheath tumor (1), lymphoid leukemia (1), fibropapilloma (1), hemangiosarcoma (1), hepatoma (1), histiocytic sarcoma (1), pheochromocytoma (1) and osteosarcoma (1).

Conclusions

The existence of a well-established Slaughterhouse Support Network allowed the compilation of comprehensive data for further epidemiological and pathological studies, particularly about less commonly reported lesions in livestock such as neoplasms in pigs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40813-021-00207-0.

Malignant Peripheral Nerve Sheath Tumour in a Seba's Short-Tailed Bat (Carollia perspicillata)

There are few reports of tumours in bats, despite the fact that members of the Chiroptera order include 22.4% of all currently known mammal species. We now describe a case of malignant peripheral nerve sheath tumour (MPNST) in an adult female Seba's short-tailed bat (Carollia perspicillata) from a private zoo in Switzerland. The macroscopical and histological findings indicated that the MPNST originated from a dorsal spinal nerve root sheath in the lumbar region and metastasized to the spleen. Immunohistochemical labelling for glial fibrillary acid protein, S100 protein, neuron specific enolase and synaptophysin was negative. The cytoplasm of a few neoplastic cells labelled for smooth muscle actin and desmin. To our knowledge, this is the first report of a PNST in a member of the Chiroptera order.

Spontaneous and Engineered Large Animal Models of Neurofibromatosis Type 1

Animal models are crucial to understanding human disease biology and developing new therapies. By far the most common animal used to investigate prevailing questions about human disease is the mouse. Mouse models are powerful tools for research as their small size, limited lifespan, and defined genetic background allow researchers to easily manipulate their genome and maintain large numbers of animals in general laboratory spaces. However, it is precisely these attributes that make them so different from humans and explains, in part, why these models do not accurately predict drug responses in human patients. This is particularly true of the neurofibromatoses (NFs), a group of genetic diseases that predispose individuals to tumors of the nervous system, the most common of which is Neurofibromatosis type 1 (NF1). Despite years of research, there are still many unanswered questions and few effective treatments for NF1. Genetically engineered mice have drastically improved our understanding of many aspects of NF1, but they do not exemplify the overall complexity of the disease and some findings do not translate well to humans due to differences in body size and physiology. Moreover, NF1 mouse models are heavily reliant on the Cre-Lox system, which does not accurately reflect the molecular mechanism of spontaneous loss of heterozygosity that accompanies human tumor development. Spontaneous and genetically engineered large animal models may provide a valuable supplement to rodent studies for NF1. Naturally occurring comparative models of disease are an attractive prospect because they occur on heterogeneous genetic backgrounds and are due to spontaneous rather than engineered mutations. The use of animals with naturally occurring disease has been effective for studying osteosarcoma, lymphoma, and diabetes. Spontaneous NF-like symptoms including neurofibromas and malignant peripheral nerve sheath tumors (MPNST) have been documented in several large animal species and share biological and clinical similarities with human NF1. These animals could provide additional insight into the complex biology of NF1 and potentially provide a platform for pre-clinical trials. Additionally, genetically engineered porcine models of NF1 have recently been developed and display a variety of clinical features similar to those seen in NF1 patients. Their large size and relatively long lifespan allow for longitudinal imaging studies and evaluation of innovative surgical techniques using human equipment. Greater genetic, anatomic, and physiologic similarities to humans enable the engineering of precise disease alleles found in human patients and make them ideal for preclinical pharmacokinetic and pharmacodynamic studies of small molecule, cellular, and gene therapies prior to clinical trials in patients. Comparative genomic studies between humans and animals with naturally occurring disease, as well as preclinical studies in large animal disease models, may help identify new targets for therapeutic intervention and expedite the translation of new therapies. In this review, we discuss new genetically engineered large animal models of NF1 and cases of spontaneous NF-like manifestations in large animals, with a special emphasis on how these comparative models could act as a crucial translational intermediary between specialized murine models and NF1 patients.

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 (p75^NTR). The spindle cells expressed S100, sex determining region Y-box 2, p75^NTR, Krox20, growth associated protein 43 and glial fibrillary acidic protein. Perineurial-like cells were positive for p75^NTR, α-smooth muscle actin and cytokeratin. Taken together, the histological und immunohistochemical findings support the diagnosis of a cutaneous pigmented neurofibroma.

Pathology and immunohistochemistry of a malignant nerve sheath tumor in a pig: case report and brief review of the literature

A 7-y-old sow with a large mass in the right upper thoracic limb was submitted for autopsy. Grossly, the mass encompassed the right humerus, elbow, and proximal radius and ulna. On cut surface, the mass was solid, lobulated, pale tan, and firm, with multifocal areas of necrosis and mineralization; it replaced the brachial musculature, invading and causing extensive humeral and ulnar osteolysis. The periosteum was roughened and irregular, and there was minor invasion into the elbow joint. Histologically, the mass was composed of densely cellular interweaving streams and bundles of pleomorphic spindle cells embedded in a scant fibrovascular stroma. There was moderate-to-strong, diffuse cytoplasmic or membranous immunoreactivity to claudin-1, laminin, and vimentin; weak-to-moderate, multifocal cytoplasmic and nuclear immunoreactivity to S100 and Sox-10, respectively, and weak cytoplasmic immunoreactivity for neuron-specific enolase. No neoplastic immunolabeling was detected with CD204, CD18, desmin, glial fibrillary acidic protein, ionized calcium-binding adapter molecule 1, melan A, neurofilament, nerve growth factor receptor, smooth muscle actin, or muscle pan-actin. A specific immunomarker for definitive diagnosis of a malignant nerve sheath tumor (MNST) and its differentiation from other nerve tumors or other spindle cell tumors is still lacking in veterinary medicine, and case-by-case or interspecies differences in immunohistochemistry (IHC) expression can occur even when applying a broad diagnostic IHC panel. However, the gross, histologic, and IHC features in our case were consistent with a MNST, an exceedingly rare neoplasm of pigs.

Malignant peripheral nerve sheath tumour in a sow

Nodular lung lesions in swine are frequently due to abscesses or granulomatous pneumonia. Although tumours are rarely reported in modern pig farming, they should be considered as a differential diagnosis when nodular lung lesions are found. A first-parity sow exhibiting respiratory signs was euthanized. Several whitish firm nodules, not encapsulated, ranging in diameter from 0.5 to 5 cm were present in all lung lobes. Microscopically, the nodules were composed of dense neoplastic cells, mainly in Antoni types A and B patterns, infiltrative and with development of emboli. All neoplastic cells stained positively by immunohistochemistry for vimentin and S-100 protein, with variable immunostaining for glial fibrillary acidic protein and stained negative for cytokeratin. Based on the gross, histological and immunohistochemical features, the tumor was diagnosed as malignant peripheral nerve sheath tumour.

Feline cutaneous nerve sheath tumours: histological features and immunohistochemical evaluations

Feline cutaneous nerve sheath tumours (CNSTs) are uncommonly reported in the skin, since they are underestimated relative to the more common spindle cell tumours of soft tissue. In this study, 26 nerve sheath tumours selected from 337 skin neoplasms of cats were examined. Histologically, they were classified into malignant (MPNSTs) and benign tumours (BPNSTs) based on degree of cellular atypia and polymorphism as well as mitotic rate and diffuse necrosis. CPNSTs were tipically characterised by Antoni A pattern, in some cases associated with Antoni B pattern. In the malignant peripheral nerve sheath tumours (MPNSTs) the polymorphism was marked, while it was mild to moderate in the benign forms (BPNSTs). In the MPNSTs the mitotic activity was generally higher than in the BPNSTs. In five cases, including three MPNSTs and two BPNSTs, there were multinucleated giant cells. Necrotic foci occurred in a BPNST and in two MPNSTs, while osseous/chondroid metaplasia was found in two cases. Immunohistochemically, all the tumours showed a marked diffuse vimentin expression. S-100 protein was expressed in 17 cases, including 81.8% of BPNSTs and 57.14% of MPNSTs. Twenty-five tumours expressed NSE and twenty-four cases showed immunoreaction for laminin. Thirteen tumours were positive for GFAP, while five tumours were positive for SMA. PGP 9.5 expression was detected in all cases, except for two MPNSTs. NGFR was expressed in eleven cases, including four MPNSTs and seven BPNSTs. Ki67 was expressed in twenty tumours without any relationship with morphologic malignancy of the neoplasm. In this case series we confirmed neoplastic spindloid cells with wavy cytoplasm arranged in compact areas, with occasional nuclear palisading or whirls, and interchanged with loosely arranged areas, as the morphological features supporting a diagnosis of CPNST. A constant concurrent expression of vimentin, NSE, and laminin might confirm the diagnosis of PNST in the absence of clear S-100 protein positivity, especially in the malignant forms. In this study, conclusive data were not obtained on the diagnostic relevance of NGFR- and PGP 9.5-expression in feline CPNSTs.

Multicentric fibromyxoid peripheral nerve sheath tumor (multicentric schwannoma) in a dromedary camel (Camelus dromedarius): morphopathological, immunohistochemical, and electron microscopic studies

During postslaughter inspection of a 4-year-old male dromedary camel (Camelus dromedarius), numerous small nodules to large masses up to 4 cm in diameter were found on the serosal surfaces of forestomachs, large intestines, mesentery, liver, and spleen. Grossly, the masses were discrete, round, smooth, and white to gray that bulged from the serosal layer. Cut surfaces of the masses were discrete, round, white, and relatively homogeneous without any necrotic foci. Histopathologically, the masses were encapsulated and composed of a mixture of round and spindle-shaped cells in loose whorls of neoplastic cells with small elongated hyperchromatic wavy nuclei and a small amount of pale eosinophilic, poorly defined cytoplasm. Masson's trichrome staining showed mild amounts of collagen fibers forming an irregular, loose stroma. In immunohistochemistry, immunoreactivity for the Schwann cell marker (S100) was diffusely positive in the neoplastic cells. The immunoreactivity for CK, c-kit, and CD34 were negative. Ultrastructural examination confirmed the tumor was entirely formed of neoplastic Schwann cells. On the basis of the histopathological, immunohistochemical, and ultrastructural findings, the tumors were diagnosed as multicentric fibromyxoid peripheral nerve sheath tumor (multicentric schwannoma). This tumor has not been previously recorded in camel worldwide.

Cutaneous Schwannomas in 22 Horses

Schwannomas are uncommonly recognized in horses. This study describes cutaneous schwannomas in 22 horses aged 8 to 25 years: 12 male, 7 female, and 3 of unknown sex. The horses had solitary cutaneous masses: 9 on the head, 3 on the neck, and the others on the shoulder, hip, thorax, abdomen, rump, extremities, or tail. The location of 1 tumor was unknown. The dermal tumors were well demarcated and expansile. Twelve had a multinodular pattern, whereas 10 formed a single nodule. Antoni A areas were observed in all tumors, and 10 tumors contained Antoni B areas. In Antoni A areas, the densely packed spindle-shaped neoplastic cells were arranged in short fascicles with nuclear palisading. In the hypocellular Antoni B areas, neoplastic cells were separated by abundant myxomatous stroma. Tumors commonly had hyalinization of stroma and vessel walls and ancient change. Cellular vacuolation was observed in 18 tumors. In all 22 cases, neoplastic cells were immunopositive for S100 protein. Expression of laminin and glial fibrillary acidic protein was observed in all 6 tumors evaluated by immunohistochemistry for these markers. One tumor was examined ultrastructurally: Neoplastic cells had branched cytoplasmic processes and were surrounded by an external lamina. Follow-up information was available 8 months to 10 years postexcision for 9 horses, for which surgical excision of the tumor was curative. The equine cutaneous schwannomas in this study had microscopic features like those of human schwannoma and had benign clinical behavior. Correct classification of equine cutaneous schwannoma will facilitate accurate prognosis and appropriate treatment.

Localized, plexiform, diffuse, and other variants of neurofibroma in 12 dogs, 2 horses, and a chicken

In humans, neurofibroma and schwannoma are distinct entities within the group of benign peripheral nerve sheath tumors. In the veterinary literature, these tumors are often classified together simply as benign peripheral nerve sheath tumors, and diagnostic criteria for their subclassification are not well established. We describe peripheral nerve sheath tumors with microscopic, immunohistologic, and ultrastructural features similar to those in subtypes of human neurofibroma in 12 dogs, 2 horses, and 1 chicken. Dogs were of different breeds and were aged 2 months to 15 years. The canine tumors were located in the skin, peripheral nerve, tongue, and large intestine. The 2 horses were 11 and 12 years old. The equine tumors were located in the subcutis of the neck and axilla. The chicken was a mature white Leghorn chicken with an ocular neoplasm. Neurofibromas of this study had localized, plexiform, diffuse and combined plexiform and diffuse growth patterns, and microscopic features similar to those in classic, collagenous, cellular, myxoid, and pigmented neurofibromas of humans. One diffuse neurofibroma contained areas of schwannian differentiation (hybrid neurofibroma-schwannoma). Two plexiform neurofibromas occurred together with diffuse ganglioneuromatosis in the large intestine of young dogs, as has also been reported in humans. This investigation shows the existence of identical subtypes of neurofibroma in animals and humans and identifies similarities in tumor location and patient age between animals and humans. This report will allow a more discriminating classification of benign peripheral nerve sheath tumors and probably has a bearing on epidemiology, pathogenesis and prognosis.

Cluster of cases of malignant schwannoma in cattle

Between 1998 and 2001, several cases of ataxia and paresis followed by recumbency and death were reported in cows from different farms in a restricted area of the Argentinian Patagonia. Five cases of this cluster were studied and a diagnosis of malignant schwannoma was established. Electron microscopy (em) of tumour samples from three of the animals revealed intracytoplasmic or interstitial structures resembling retroviral particles. Attempts to isolate a viral agent from the tumours were unsuccessful but the epidemiological data and the em findings suggest a viral aetiology.

Multicentric malignant Schwannoma in a crossbred cow

Multicentric malignant Schwannoma in a crossbred cow is described. Multiple and solitary nodules of varying sizes were seen to be distributed throughout the body of the animal, mainly along the peripheral nerves supplying the muscles of the thoracic and abdominal regions and the skin. Multiple nodules were also observed in the hilus of the liver. The mediastinal lymph nodes were replaced by a large solitary tumorous mass. Multiple neoplastic linear cords with small nodules were observed on the pericardium. Histologically, the nodules showed mainly densely packed, spindle-shaped cells arranged in short interwoven bundles and whorls (Antoni type A pattern). Stellate, spindle-shaped and round or oval tumour cells proliferated haphazardly within the loose texture of a collagenous matrix (Antoni type B pattern). Immunohistochemically, in both Antoni type A and type B areas, neoplastic cells reacted with antibodies against S-100 protein. Based on the metastasis of the tumour to the lymph nodes and on histology, the neoplasm was diagnosed as a multicentric malignant Schwannoma.

Feline periocular peripheral nerve sheath tumor: a case series

The objective of this retrospective study was to describe signalment, clinical presentation, surgical treatment, outcome, histopathologic, and immunohistochemical characteristics of periocular peripheral nerve sheath tumor in a series of cats. Six cats with a histologic diagnosis of peripheral nerve sheath tumor of the eyelid and/or conjunctiva were identified from 3997 feline ocular histopathologic submissions to the Comparative Ocular Pathology Laboratory of Wisconsin between 1976 and 2002. Medical records were reviewed and data were collected for signalment, eye affected, location, duration, and history of tumor recurrence. Ancillary diagnostic tests, surgical approach, and histopathology were also described. Special stains and immunohistochemistry panels were performed on the tissue. Follow-up information was obtained through telecommunications with the owner and local veterinarian. The mean age of the cats was 8 years (range: 5-15 years). There was an equal distribution of males and females. Breeds represented were two Domestic Long-haired (DLH) cats, three Domestic Short-haired (DSH) cats, and one Manx. The right eye was affected in four cats and the left eye in two cats. The superior eyelid was affected in four cats, the superior conjunctiva in two cats, and the inferior eyelid in one cat. All of the cats that underwent surgical excision, cryoablation, or laser ablation had an average of three recurrences of the tumor. Four of six cats undergoing wide excision with enucleation, exenteration or rhomboid flap had no recurrence of the tumor. Histomorphologically, all of the tumors were of spindle cell type with five of six tumors showing histologic features of Antoni type B tissue. All six tumors stained positive for vimentin. Five of six tumors stained positive for S-100 and laminin. All six tumors were negative for smooth muscle actin. Definitive histologic diagnoses of spindle cell tumors can be difficult. The presence of Antoni A and B histologic patterns as well as immunohistochemical reactivity for vimentin, S-100, and laminin suggest a diagnosis of peripheral nerve sheath tumor. Our findings suggest that local aggressive recurrence is common and that wide surgical excision combined with enucleation or exenteration may be indicated.

Immunohistochemical evaluation of canine peripheral nerve sheath tumors and other soft tissue sarcomas

Seventeen cases of canine peripheral nerve sheath tumors (PNSTs), 11 malignant PNSTs (MPNSTs), and six benign PNSTs (BPNSTs) were examined. The prognosis in five of six dogs with BPNSTs was excellent, whereas all dogs with MPNSTs died within 2 years after the last surgical resection. One BPNST formed a recurrent mass with features of a MPNST. Histopathologically, the predominant tumor cell of MPNSTs was either spindle or round in shape with epithelioid characteristics. Other atypical cells had abundant granular cytoplasm or were multinucleated giant cells with periodic acid-Schiff-positive cytoplasmic globules. Furthermore, two MPNSTs contained cartilaginous and osseous metaplasia. On the contrary, most BPNSTs exhibited typical features of schwannoma or neurofibroma, whereas two BPNSTs had atypical morphology. One BPNST consisted of epithelioid cell proliferation with some tumor cells revealing nuclear atypia. Immunohistochemically, the expression of vimentin (100%), S-100 (73%), nerve growth factor receptor (NGFR, 64%), and myoglobin (64%) was commonly found in MPNSTs. The two BPNSTs with atypical histologic appearances were positive for vimentin, S-100, NGFR, and neuron-specific enolase, and one of these had moderate immunoreactivity for cytokeratin. Most BPNSTs were positive for glial fibrillary acidic protein, as well as S-100 and NGFR. Although most rhabdomyosarcomas (RMSs) and canine hemangiopericytomas (CHPs) also showed focal immunoreactivity for S-100, most RMSs were intensely positive for myoglobin and negative for NGFR. Most CHPs (80%) exhibited focal alpha-smooth muscle actin (alpha-SMA) expression, whereas all PNSTs were negative. These results indicate that immunohistochemistry for NGFR and alpha-SMA might be useful for differentiating canine PNSTs from RMSs or CHPs, respectively.

Immunohistochemical characterization of tumor cells and inflammatory infiltrate associated with cutaneous melanocytic tumors of Duroc and Iberian swine

The immunophenotype of tumor cells and inflammatory infiltrate associated with cutaneous melanocytic lesions (29 melanocytomas, two malignant melanomas, and 23 residual lesions) from 54 adult Iberian and Iberian x Duroc pigs were examined using a panel of nine antibodies. All neoplastic cells were vimentin+, cytokeratin-, and alpha-1-antitrypsin- and the majority were S100+, whereas all pigmented macrophages were vimentin+, cytokeratin-, and S100- and most expressed alpha-1-antitrypsin. Regressing tumors were characterized by zones with low density of neoplastic cells accompanied by heavy infiltration of CD3+ T lymphocytes, whereas zones with high density of neoplastic cells showed very low numbers of CD3+ T lymphocytes. The infiltrate of CD79a+ B cells and IgG, IgM, and IgA plasma cells was low. The majority of lymphocytes of the peri- and intratumoral infiltrate were major histocompatibility complex class II+, but neoplastic cells did not express class II antigen. The 17 residual lesions examined were composed of macrophages containing abundant melanin pigment and low to moderate numbers of CD3+ T lymphocytes. The results of the present study suggest that the local cellular immune response plays a crucial role in the host response that induces regression of cutaneous melanomas and melanocytomas of the Iberian and crossbred Iberian x Duroc pigs.

Point mutation of neu oncogene in animal peripheral nerve sheath tumors

Thirty-four peripheral nerve sheath tumors of four domesticated animal species were characterized and assayed for point mutation of the neu oncogene. Based on their morphoimmunophenotype, 32 tumors were classified as schwannomas. Schwannoma morphology was characterized by the presence of Antoni type A and B pattern and immunoreactivity for S-100 protein and vimentin. Two anaplastic and metastatic tumors originating from spinal cord root, immunonegative for S-100 protein and positive for vimentin, were classified as malignant peripheral nerve sheath tumors (MPNSTs). Four malignant schwannomas and two MPNSTs expressed a point mutation of the neu oncogene by the polymerase chain reaction-restriction fragment length polymorphism method. The finding of neu oncogene mutation could be a useful diagnostic genetic marker in the malignant form of peripheral nerve sheath tumors in animals.

Porcine circovirus induces B lymphocyte depletion in pigs with wasting disease syndrome

To disclose the mechanism of cellular injury following porcine circovirus (PCV) infection, 12 pigs were examined by the terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) method and immunohistochemistry. Histologically, the lymphoid tissues were characterized by marked apoptosis of lymphocytes, lymphocyte depletion, and macrophages and giant cells containing numerous inclusion bodies with or without apoptotic bodies. Immunohistochemically, there were many lysozyme-positive macrophages in the lymphoid follicles, while the number of CD79a-positive B lymphocytes was scanty. Apoptotic cells, which were proved to be TUNEL positive, revealed CD79a positivity. Although detectable mainly in the cytoplasm of macrophages, PCV antigens were found also in the nuclei of macrophages and apoptotic lymphocytes. Ultrastructurally, the presence of PCV virions was confirmed in apoptotic bodies phagocytosed by macrophages. These findings suggested that lymphocyte depletion with apoptotic death of B lymphocytes was caused by PCV, and that some of the inclusion bodies were phagolysosomes derived from the apoptosis. Thus, PCV may trigger the development of wasting disease syndrome by producing an immunocompromised state in pigs.

Malignant schwannoma in a red deer (Cervus elaphus)

A five-year-old female red deer (Cervus elaphus) was in poor condition and severely lame on the left hindleg owing to a 19.4 cm x 15.9 cm mass involving and destroying the distal end (head) of metatarsal bones III and IV, the proximal sesamoid bones and the first phalanges (III and IV). The histopathological analysis revealed a spindle cell tumour with frequent palisade arrangement (Antoni type A pattern), and with highly anaplastic tumour cells in some areas. Structures resembling peripheral nerves were identified within the tumour. The neoplastic cells reacted with vimentin in a cytoplasmic pattern, and almost all of them reacted with S-100 protein in a nuclear and cytoplasmic pattern and did not express neurofilament, glial fibrillary acidic protein or keratins. This immunophenotype and the histopathological features were consistent with a diagnostic of malignant schwannoma. It was atypical because of the species affected, the location and the local malignancy.

Multiple peripheral nerve sheath tumors in the small intestine of a horse

Multiple neurofibromas, schwannomas, and hyperplastic enteric plexuses were observed in the distal jejunum and ileum of a 6-year-old pinto gelding. The animal was presented because of an acute episode of colic. Three meters of distal small intestine, partially incarcerated in the epiploic foramen, were surgically removed. Numerous tumor nodules up to 10 mm in diameter were found adjacent to a Meckel's diverticulum, predominantly located in the subserosa of a hypertrophic segment. Histologically, tumors were well demarcated and composed of interlacing fascicles formed by spindloid cells. Adjacent enteric plexuses were hyperplastic. Immunohistochemically, all tumors were positive for vimentin and S-100. Desmin immunoreactivity was only observed in larger tumors (> 500 microns). Glial fibrillary acid protein was demonstrated nearly exclusively in smaller ones. Immunostaining for neurofilament was restricted to entrapped ganglion cells. Based on conventional light microscopic examination and immunohistochemical evaluation, the lesion was diagnosed as multiple benign peripheral nerve sheath tumors in the small intestine.