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.     

Morphologic and immunohistochemical features of two spontaneous peripheral nerve tumors in Wistar rats

Morphologic features and S-100 protein immunoreactivity of a benign and malignant peripheral nerve sheath tumor were studied in two Wistar rats. Neoplasms that developed in untreated control rats from tumor bioassays were S-100 protein positive and had similar histopathologic features. Each peripheral nerve sheath tumor was encapsulated and composed of spindle cells arranged around small thin-walled blood vessels. Palisaded tumor cells were in the benign peripheral nerve sheath tumor while cells of the malignant peripheral nerve sheath tumor had cellular atypia and moderate numbers of mitoses. Ultrastructural examination of the malignant peripheral nerve sheath tumor revealed cells with external lamina and interdigitation of cytoplasmic processes. Intracytoplasmic concentric lamellae were seen; they were regularly spaced with a periodicity of about 15 nm. Such structures, indistinguishable from myelin sheaths, have not been commonly associated with peripheral nerve sheath tumors in man. Electron microscopy and immunohistochemistry were useful in the diagnosis of these tumors as Schwannomas and in differentiation from other spindle cell tumors.     

Malignant peripheral nerve sheath tumour of the urinary bladder in a cat

A 14-year-old domestic shorthair cat presented with a 5-month history of urinary incontinence and inappro-priate elimination. Ultrasonography revealed a well-marginated, vascular mass of mixed echogenicity ex-tending from the dorsal wall of the urinary bladder into the lumen. Partial cystectomy was performed for re-moval of the urinary bladder mass; histopathological evaluation revealed a spindle cell neoplasm with a prominent palisading pattern. Histomorphologic features and immunohistochemical demonstration of vimentin, glial fibrillary acidic protein and S-100 protein, combined with negativity for smooth muscle actin and desmin were consistent with malignant peripheral nerve sheath tumour. This case report describes a novel location of malignant peripheral nerve sheath tumour; to the authors' knowledge, the bladder has not been described as a site of origin in the cat or any other domestic species.     

Of all the nerve! A subcutaneous forelimb mass on a cat

A 16-year-old, male, neutered cat had a 2.5 X 1.5 cm mass on the medial aspect of the right carpus. Cytologic examination of a fine-needle aspirate of the mass indicated a markedly pleomorphic population of plasmacytoid to histiocytic-appearing cells. The cytologic diagnosis was malignant neoplasia of probable mesenchymal or round cell origin. The right forelimb was surgically removed and the scapular, axillary, and prescapular lymph nodes were excised. Malignant fibrous histiocytoma was tentatively diagnosed histologically; however, the tumor cells subsequently were found to be negative for histiocytic (MAC 387, antitrypsin), T-cell (CD3), and B-lymphocyte (immunoglobulin light chains, Ly 5/CD45R) markers, and positive for glial fibrillary acidic protein, vimentin, and S-100. Based on the immunohistochemical results, the diagnosis was modified to malignant peripheral nerve sheath tumor (PNST). Six months after surgery, the cat was reported to be well and had no evidence of metastasis. PNSTs are rare tumors in cats, and are considered as synonymous with schwannomas, neurofibrosarcomas, and hemangiopericytomas. In this cat, the plasmacytoid and pleomorphic appearance of the PNSTcells in cytologic and histologic specimens was unusual, and made it difficult to reach an accurate diagnosis without immunocytochemistry.     

A simple and rapid immunocytochemical technique for detection of cytokeratin, vimentin, and S-100 protein in veterinary diagnostic cytology

The objective of this study was to establish a simple and rapid immunocytochemical technique that can be used in veterinary diagnostic cytology. Air-dried impression smears were collected from canine tumors. Samples of epithelial tumors, mesenchymal tumors, and malignant peripheral nerve sheath tumors and melanomas were used for detection of cytokeratin, vimentin, and S-100 protein, respectively. The labeled streptavidin-biotin system was used in the present study. Optimal fixation was determined using standard immunocytochemical procedures, and acetone fixation was found to be the most effective. Optimal concentrations of primary and secondary antibodies were determined at a preset 5-min incubation. Omission of H(2)O(2) treatment, shortening the time for blocking and labeled-streptavidin incubation, and simplifying washing did not decrease immunopositive intensities or enhance false-positive reactions. The described rapid protocol requires approximately 45min without the use of any special equipment.     

Immunohistochemistry for 2',3'-cyclic nucleotide-3'-phosphohydrolase in 63 bovine peripheral nerve sheath tumors

To establish a simple and uniform classification of bovine peripheral nerve sheath tumors (PNSTs), 63 tumors from 44 cattle were examined histologically and immunohistochemically with antibodies against S100 protein and 2',3'-cyclic nucleotide-3'-phosphohydrolase (CNPase). Immunohistochemically, all the tumors were positive for S100 protein, CNPase, or both. Four types of PNST were recognized: 35 schwannomas, 9 neurofibromas, 14 hybrid (neurofibroma-schwannoma) tumors, and 5 malignant PNSTs. Axons were identified by immunohistochemistry for neurofilament in a proportion of tumors of each type of PNST. In conclusion, bovine PNSTs commonly have both schwannomatous and neurofibromatous areas. Moreover, the Schwann cell markers S100 protein and CNPase, in combination with antibodies against neurofilament, are valuable diagnostic tools to classify bovine PNSTs.     

Primary malignant peripheral nerve sheath tumor with eosinophilic cytoplasmic globules arising from the greater omentum in a dog

A 10-year-old Golden Retriever dog had a solitary tumor mass arising from the greater omentum. Histologically, the tumor showed varying cellularity and patterns of cellular arrangement. In dense cellular areas, spindle-shaped cells were arranged in interlacing bundles. The sparse cellular area was characterized by loosely arranged fusiform cells. The neoplastic cells frequently contained PAS-positive eosinophilic globules in the cytoplasm, and mitotic figures were frequently observed. The tumor cells were positive to vimentin, S-100 protein, glial fibrillary acidic protein, myelin basic protein, neuron-specific enolase and myoglobin. The present tumor was diagnosed as a malignant peripheral nerve sheath tumor (MPNST) with eosinophilic cytoplasmic globules arising from the greater omentum. To our knowledge, this may be the first case of primary omental MPNST in domestic animals.     

A canine peripheral nerve sheath tumor including peripheral nerve fibers

Peripheral nerve sheath tumor was found in a 7-year-old male mongrel dog. The tumors were located in the right cheek subcutis and oral submucosa. Histologically, neoplastic cells were arranged in streaming bundles, occasionally interlacing bundles or whorls of elongated and spindle cells. Cellular atypia was poor and mitotic figures were rarely observed. Ultrastructurally, neoplastic cells had basement membrane, typical of Schwann cells. One bundle of normal peripheral nerve fibers and some myelinated axons were seen within the tumor tissues. Immunohistochemically, neoplastic cells reacted to vimentin, glial fibrillary acidic protein, S-100 protein and neuron specific enolase. In addition to the above immunoreactions, the included nerve fibers were positive for myelin basic protein and neurofilament protein. This paper also discusses immunohistochemical findings on differential diagnosis in comparison with those of canine hemangiopericytomas reported hitherto.     

Soft tissue sarcomas in the African hedgehog (Atelerix albiventris): microscopic and immunohistologic study of three cases.

Three soft tissue tumors from 2 female hedgehogs were examined microscopically and immunohistochemically. Two tumors involved haired skin and the third one was vaginal. Microscopically, the cutaneous tumors had features of malignant peripheral nerve sheath tumor (MPNST), whereas the vaginal tumor was classified only as a spindle cell sarcoma. Immunohistochemically, all 3 tumors were strongly positive for vimentin and strongly to moderately positive for CD10 and neuron-specific enolase but did not stain with antibody to S100 protein, an antigen typically present in human MPNST The cutaneous tumor from hedgehog no. 1 was examined ultrastructurally and the neoplastic cells resembled fibroblasts. Hedgehog no. 1 was euthanized at the time of the biopsy. The outcome of the other hedgehog was unknown.     

Morphology and classification of 96 primary cardiac neoplasms in Fischer 344 rats

Ninety-six primary cardiac neoplasms were identified from 79,971 Fischer 344 (F344) rats used in chronic toxicity and carcinogenicity studies by the National Toxicology Program (NTP) and National Cancer Institute (NCI), for an overall incidence of 0.1%. Neoplasms were classified as: 60 endocardial schwannomas, 23 intramural schwannomas, eight atriocaval mesotheliomas, three paragangliomas, one pericardial mesothelioma, and one hemangioma. Metastases occurred in four rats with endocardial schwannoma. Histological appearance of the endocardial and intramural schwannomas was consistent with origin from nerve sheath. Two of six endocardial schwannomas available for immunohistochemical staining were weakly positive for S-100 antigen. The atriocaval mesotheliomas, while morphologically resembling adenocarcinoma, were positive for vimentin and keratin, indicating mesothelial origin. Seventy of the 96 cardiac neoplasms occurred in rats 2 years of age or older at time of death. There were no sex or treatment-related differences in the incidence of these neoplasms, with the exception of atriocaval mesothelioma, which was more common in males.     

Intratesticular benign peripheral nerve sheath tumour in a ferret (Mustela putorius furo)

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.     

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.     

Intraocular peripheral nerve sheath tumor in a dog

A tumor within the right globe in a 9-year-old Shetland sheepdog was examined pathologically. The tumor was composed of spindle or oval cells arranged in interwoven bundles with intervening collagenous or mucinous matrices. Immunohistochemically, the tumor bound antibody directed to S-100 protein and vimentin, but not to desmin, actin smooth muscle, or neurofilament. Electron microscopy revealed that the tumor cells had poorly developed cytoplasmic processes, desmosomes between closely contiguous cells, and a discontinuous basement membrane-like material. Based on these findings, the tumor was diagnosed as a peripheral nerve sheath tumor (PNST) histologically. To the authors' knowledge, this is the first reported case of intraocular PNST in dogs.     

Feline intraocular tumors may arise from transformation of lens epithelium

Feline ocular sarcomas are malignant intraocular neoplasms that are frequently associated with a history of ocular trauma. They usually present as fibrosarcomas, but some have both epithelial and mesenchymal features. The purpose of this study was to determine the cell of origin of a subset of feline intraocular sarcomas that display a mixed epithelial-mesenchymal phenotype, with elaboration of basement membrane-type matrix. We examined the morphology and histochemical and immunohistochemical phenotypes of nine feline intraocular sarcomas. Immunohistochemistry and in situ hybridization were performed to detect expression of crystallin alpha A. In addition, tumors were examined for expression of vimentin, cytokeratin, smooth muscle actin, desmin, melan A, neural cell adhesion molecule, S-100, glial fibrillary acidic protein, nerve growth factor receptor, and collagen type IV. Animals ranged from 7 to 17 years of age--no breed or sex predilection for tumor occurrence was present. Tumors were characterized by mixed epithelial and mesenchymal phenotypes, both of which elaborated basement membrane-type material and expressed vimentin highly. On the basis of collagen type IV and crystallin alpha A immunopositivity, we established that three of nine tumors were of lens epithelial origin. Expression of desmin and smooth muscle actin identified one tumor as a leiomyosarcoma. The remainder were undifferentiated sarcomas of myofibroblastic origin. This is the first report of lens epithelial neoplasia in clinical material from any species. The history and morphologic features of feline ocular sarcomas are reminiscent of feline vaccine-induced sarcomas. These tumors may share pathophysiologic similarities unique to this species.     

Endocardial schwannomas in the Wistar rat

Endocardial neoplasms were observed in 13 Wistar rats, 15-30 months old, from a 30-month inhalation study. Eight of the rats were dissected at 30 months and the other five between 15 and 29 months. Histologically, the lesions in the heart were diagnosed as endocardial schwannomas. Two of the 13 schwannomas were malignant, while the rest were benign. One malignant schwannoma metastasized to the thymus and the other metastasized to the aorta, oesophagus, liver and spleen. Some schwannomas appeared as early lesions limited to the endocardium consisting of round to ovoid cells interspersed with spindle cells, while other schwannomas appeared as advanced lesions consisting of a thin superficial layer of round to ovoid cells and a deeper layer of spindle cells characteristic of endocardial schwannomas. The histological appearance of the metastases was identical to that of the primary tumour. The diagnosis was confirmed by positive immunostaining for S-100 protein. The incidence of endocardial schwannomas in the Wistar rat strain was 1.8%.     

Metastasizing fibrosarcoma in a Wistar rat--case report

A 19-month-old male control Wistar rat from a 30-month inhalation study showed a subcutaneous greyish-white mass extending from the throat to the thoracic cavity. The rat had been euthanized because of its poor general condition. Histologically, the mass was diagnosed as a fibrosarcoma infiltrating the masseter muscle with metastases in the lungs, liver and heart. The primary tumour was characterized by fusiform spindle cells producing various amounts of interlacing bundles of collagen. The cells formed a characteristic herringbone pattern and mitotic figures were frequent. The histological parameters of the metastases were practically identical to those seen in the primary tumour. The diagnosis was confirmed by trichrome staining and positive immunostaining for vimentin and was differentiated from leiomyosarcomas by its negative immunostaining for desmin, from schwannomas by its negative immunostaining for S-100 and from malignant fibrous histiocytomas by the absence of giant cells. The incidence of fibrosarcomas in Wistar rats is very low (up to 3%) and metastasis is rarely observed.     

Subcutaneous Soft Tissue Sarcoma with Rhabdoid Features in a Dog

A nine-year-old male beagle dog had a white spherical mass in the subcutis of the left lumbar region. Microscopically, spindle to oval cells diffusely proliferated in the fibrous and myxoid stroma. Many neoplastic cells showed rhabdoid features or vacuolated cytoplasm. Immunohistochemically, the neoplastic cells were positive for vimentin and S100 and partly positive for neuron-specific enolase and glial fibrillary acidic protein but were negative for von Willebrand factor, desmin and α-smooth muscle actin. Ultrastructurally, the neoplastic cells had abundant cytoplasmic processes and desmosome-like structures. Cytoplasmic inclusions of rhabdoid-featured cells in HE sections were composed of aggregates of intermediate filaments, and cytoplasmic vacuoles were identified as an invagination of cytoplasm. Although malignant peripheral nerve sheath tumor was suggested according to these results, the present case was diagnosed as a soft tissue sarcoma with rhabdoid features due to a lack of identification of the basal lamina under electron microscopy.     

Immunohistochemical and ultrastructural investigation of granular cell tumours in dog, cat, and horse.

Six canine, one feline and one equine granular cell tumours (GCTs) were investigated electron microscopically and immunohistochemically. The tumours were tested for reactivity with monoclonal antibodies against vimentin and desmin and with polyclonal antibodies against cytokeratin, S-100 protein, glial fibrillary acidic protein (GFAP) and neuron specific enolase (NSE). All GCTs were characterized by their PAS positive cytoplasmic granules in light microscopy, which in electron microscopy appeared as lysosome-like granules. In each case two canine GCTs were stained by the antibody against cytokeratin, vimentin and S-100 protein. Cells of the equine GCT showed reactivity with the antiserum against S-100 protein. In the feline GCT no reactivity with any of the antibodies tested was observed. These differences of the immunohistochemical reactions of GCTs suggest a nonuniform histogenesis of GCTs in domestic animals. The reactivity of the tumour cells with the antiserum against NSE is discussed.     

Expression of S100a, vimentin, NSE, and melan A/MART-1 in seven canine melanoma cells lines and twenty-nine retrospective cases of canine melanoma

We evaluated the expression of vimentin, S100a, and Melan A/MART-1 (melanoma antigen recognized by T cells 1) in seven cell lines established independently from dogs with canine melanoma. We also compared routine immunostaining of 29 clinical specimens from melanoma cases using vimentin, S100a, and neuron-specific enolase (NSE) with staining for Melan A/MART-1 as part of a diagnostic panel. All the cell lines were positive for expression of vimentin and S-100a. MelanA/MART-1 expression was seen consistently in only two of the seven cell lines. Staining for Melan A/MART-1 was most intense near areas of heavy melanin pigmentation. All except one of the clinical specimens were positive for vimentin. S 100a was expressed in the majority of both pigmented (15/20, 75%) and amelanotic (8/9, 88.8%) tumors. Seventeen of 29 (58.6%) tumors were positive for NSE. Melan A/MART-1 was expressed in 18/29 (62%) tumors, including 90% of pigmented tumors, but in no amelanotic tumors. Intensity of Melan A/MART-1 staining correlated positively with biologic behavior, with seven malignant tumors showing negative to weak staining and 10 benign tumors showing moderate to strong staining. Three malignant tumors showed moderate to intense staining for Melan A/ MART-1. Our results suggest that expression of Melan A/MART-1 may be unstable in cultured cell lines. Assessment of both S100a and Melan A/MART-1 expression is useful to confirm a diagnosis of canine melanoma, and Melan A/MART-1 may be especially informative regarding the biologic behavior of these tumors.     

Malignant peripheral nerve sheath tumor as a cause of chronic cardiac insufficiency in cattle

Chronic cardiac insufficiency was associated with a malignant peripheral nerve sheath tumor in a cow. An eight-year-old cow developed a progressive condition (over a period of three months) characterized by an enhanced abdominal volume, reluctance to move, a positive jugular pulse, watery diarrhea and death. At necropsy, moderate subcutaneous edema and an enhanced hepatic lobular pattern were observed. A 23x20x11 cm firm, grayish-white mass adhered to and infiltrated the right atrium. Multiple firm, yellowish-white nodules of 0.5 to 12 cm in diameter were diffusely scattered in the epicardium and parietal pericardium. Histologically, the tumor was poorly circumscribed with foci of infiltration of the myocardium. The neoplastic cells had two major histologic patterns, Antoni types A and B. Within occasional foci, pleomorphic cells with an epithelioid appearance were present in addition to multinucleated cells with periodic acid Schiff (PAS)-positive cytoplasmic globules. Foci of cartilaginous and granular differentiations were interspersed among the neoplastic cells. Multiple vessels presented wall hyalinization and tumoral embolus. Large necrotic foci with mineralization and cholesterol clefts were also observed. Immunohistochemically, the tumor was positive for S100 protein, vimentin and neuron-specific enolase labeling.