Olfactory neuroepithelioma in a dog: an immunohistochemical and electron microscopic study

A case of olfactory neuroepithelioma was investigated electron microscopically and immunohistochemically. The tumor mass was found in the nasal cavities of a 10-year-old female dog, which showed epistaxis, nasal discharge and facial swelling. The tumor tissue consisted of tubular structure of cuboidal to columnar cells and compactly arranged nests of small cells surrounded by a fibrovascular stroma. Mitotic figures were frequently observed. Immunohistochemically, the tumor cells frequently showed positive for neurofilament protein, synaptophysin and/or carnosine in addition to keratin. Ultrastructurally, tight junction was observed between the tumor cells. No dense-cored secretory granules were shown in the tumor cells. These findings indicated that the present tumor had neuronal and epithelial features probably originating from the olfactory epithelium.     

Peripheral giant cell granuloma in a cat

A gingival mass excised from a cat was determined to be a peripheral giant cell granuloma. Characteristic histologic features were large numbers of multinucleated giant cells intermixed with mononuclear mesenchymal cells in a loose fibrovascular stroma. The lesion recurred twice, indicating that these non-neoplastic growths may be locally invasive.     

Intracranial granular cell tumor in a dog

A 12-year-old female miniature poodle showed a 3-month history of neurological signs. Magnetic resonance imaging disclosed a high intensity tumor mass in the right cerebral hemisphere with compression of the lateral ventricle. At necropsy, a 2 x 3 cm white, friable mass was found in the right ventral pyriform lobe. Microscopically, the tumor cells were large, polygonal to round cells supported by a sparse fibrovascular stroma. The tumor cells typically possessed finely granular, pale eosinophilic cytoplasm with strongly positive periodic acid-Schiff (PAS) reaction. The tumor cells were immunopositive for vimentin, NSE and S-100. Ultrastructurally, the tumor cells showed large amounts of granules in the cytoplasm, and absence of basement membrane. Based on the above-mentioned findings, the intracranial granular cell tumor was diagnosed.     

Osteoclastic-like giant cell tumour in a cat

An 11-year-old neutered male domestic shorthair cat was presented with an epulis. A hemispherical mass, 8mm in maximum diameter, without a peduncle and bright reddish in colour, was observed on the gingiva of the left mandible. Radiography failed to show any infiltrating osteolysis. The epulis was surgically removed via gingival incision around the margin to the depth of connective tissue layer. Histopathological examination indicated that the epulis contained a large number of multinucleated giant cells (MGCs) intermixed with mononuclear mesenchymal cells in a loose fibrovascular stroma. Mitotic cells were found, mainly in the centre of the mass. MGCs were stained positive by the tartrase resistant acid phosphatase (TRAP) staining, indicating osteoclasts activity. Immunohistochemical staining for proliferating-cell nuclear antigen (PCNA) was observed within the majority of mononucleated cells, whereas multinucleated cells did not stain. An osteoclast-like giant cell tumour was concluded in this case. The origin of epulis is likely from the periosteal tissue. The cat recovered uneventfully and no recurrence has been noted for 3 years thereafter.     

Spontaneous pinealoma in a male Crj:CD (SD) IGS rat

A pinealoma (benign) was found in a 61-week-old male Crj:CD (SD) IGS rat. The neoplasm was located between the cerebral hemispheres and the cerebellum. Histologically, the tumor cells consisted of two cell types: large, pale-staining cells and small dark-staining cells. A fibrovascular stroma divided the tumor cells into incomplete lobules or nest structures. Relatively numerous mitoses were noted in the tumor cells. Ultrastructurally, the tumor cells contained dense-cored vesicles, approximately 120 nm in diameter.     

Pathologic and immunohistochemical findings in a feline aortic body tumor

The presence of a heart-base tumor was diagnosed by ultrasound imaging in a 10-year-old, female, domestic shorthaired cat presenting with dyspnea and pleural effusion because of the presence of a modified transudate. Hematology and clinical chemistry were unremarkable. The owner elected euthanasia. At necropsy, a locally extensive, firm, multilobulated nodule surrounded the pulmonary vein. The tumor was composed of lobules of large polygonal cells separated by a fine fibrovascular stroma. Tumor cells infiltrated the myocardium, and neoplastic emboli were present, but no metastases were macroscopically detectable. Tumor cells were immunohistochemically positive for chromogranin A, for synaptophysin and, faintly, for neuron-specific enolase and negative for vimentin, cytokeratin, alpha smooth muscle actin, glial fibrillary acidic protein, thyreoglobulin, and calcitonin. Based on histologic and immunohistochemical findings, the diagnosis of chemodectoma was made.     

Cytologic,histologic, and immunohistochemical features of maxillofacial alveolar rhabdomyosarcoma in a juvenile dog

Abstract: A 15‐month‐old castrated male dog with a history of intermittent epistaxis and sneezing was admitted for the examination of a maxillofacial mass. An impression smear of a biopsy sample from the cauliflower‐shaped gingival mass contained numerous round cells, 5–25 μm in diameter, which contained a moderate amount of clear to pale blue cytoplasm and resembled lymphoid cells. Mitotic figures were frequently observed. The mass was diagnosed as malignant round cell neoplasia. On histologic examination the tumor was composed of diffusely arranged, small, atypical round cells with a small amount of fibrovascular stroma. Immunohistochemically, the cells were negative for CD3, CD18, CD20, CD79α, cytokeratin, melan‐A, chromogranin A, α‐smooth muscle actin, and myoglobin but positive for vimentin and desmin. The cells also had strong positive nuclear staining for myogenin and MyoD1. A diagnosis of solid‐pattern alveolar rhabdomyosarcoma was made on the basis of morphologic and immunohistochemical results. Alveolar rhabdomyosarcoma should be considered in the differential diagnosis of tumors in juvenile dogs, especially when cytologic findings reveal round, undifferentiated cells.     

Invasive ductal carcinoma of the mammary gland in a mare

A 21-year-old thoroughbred mare had a 35 x 14 x 10 cm mass involving the mammary gland. Metastases were found in the kidneys, lungs, skeletal muscles, and regional lymph nodes. Histopathologic examination of the tumor revealed a ductal solid carcinoma with extensive intraductal and intralobular involvement and focal infiltration of the adjacent stroma. The intralobular neoplasms were divided into irregularly shaped islands and sheets of polygonal and spindle-shaped epithelial cells by thick or thin fibrous connective tissue bundles. The neoplastic cells had a small or moderate amount of cytoplasm that stained faintly with eosin and round or oval hyperchromatic nuclei. Immunohistochemically, the neoplastic cells were strongly positive for Lu-5, weakly positive for AE1/AE3, vimentin, and glial fibrillary acidic protein, and negative for cytokeratin 8, cytokeratin 14, alpha-smooth muscle actin, calponin, and S100. The neoplasm was diagnosed as an invasive ductal carcinoma of the mammary gland with multiple metastases.     

Peripheral neuroblastoma in a young labrador retriever

A 2-year-old Labrador Retriever developed atrophy of the right temporal muscle, subsequently showed generalized seizure and died 2 months after the clinical onset. Postmortem examination revealed the tumor masses in the right mandibulopharyngeal area, nasopharynx and intracranial space. Histopathologically, these tumor masses were composed of small round neoplastic cells and neuropil-like stroma separated by fibrovascular septa. In the neoplastic masses, small neoplastic cells with round to oval hyperchromatic nuclei and scanty cytoplasm predominated, and angulated neoplastic cells with larger nuclei and moderate cytoplasm were scattered. Immunohistochemically, neoplastic cells were positive for neuron specific enorase, neurofilament protein, chromogranin A, synaptophysin and tyrosine hydroxylase. Based on these findings, this case was diagnosed as peripheral neuroblastoma, presumably originated from the sympathetic ganglion, maybe right craninal cervical ganglion.     

Spontaneous necrotizing sialometaplasia of the submandibular salivary gland in a Beagle dog

A single mass was found on the left submandibular salivary gland at necropsy of a 15-month-old male commercially bred laboratory Beagle dog from a control dose group from a repeat toxicity study. Microscopically, the mass was composed of a well-demarcated area of coagulative necrosis surrounded and separated from the normal salivary gland tissue by a thick fibrovascular capsule. Necrosis was admixed with areas of hemorrhage, fibrin, edema, fibrinoid necrosis of the vascular tunica media, and thrombosis of small and large vessels. Within the necrotic tissue, there was marked ductal hyperplasia, and squamous metaplasia of duct and acinar epithelium. The mass was diagnosed as necrotizing sialometaplasia of the submandibular gland. Hyperplastic ductal elements and squamous metaplasia can be mistaken microscopically with squamous cell carcinoma. Therefore, pathologists should be aware of this lesion as to avoid errors in the diagnosis of this benign pathologic condition.     

Histopathological and immunohistochemical studies of apocrine sweat gland adenocarcinomas in cats

Seven adenocarcinomas of apocrine sweat glands among the 67cutaneous tumours of cats were evaluated between 1980 and 2005. Histopathologically, three tumours were solid, tubular, tubular‐ductal, tubular‐cystic and papillar‐cystic types were also diagnosed each one. Cuboidal and squamous epithelial cells surrounding the cystic lumina and their papillar extensions into the cyst lumens were evident in almost all tumour types. Besides, fibrovascular stroma which surrounding neoplastic foci showed proliferation and stromal invasion. Immunohistochemical features of these tumours were examined with pan‐cytokeratin, vimentin and carcinoembryonic antigen.     

Ovarian mucinous cystadenoma with smooth muscle proliferation in a cynomolgus monkey (Macaca fascicularis)

An ovarian mucinous cystadenoma was found in a 5-year-old female cynomolgus monkey (Macaca fascicularis). The tumor was composed of various sizes of multilocular cystic glands lined by a single layer of mucin-filled epithelium. Each of these cystic glands was surrounded by a large amount of solid fibrous stroma resembling smooth muscle. The ovarian surface epithelium showed partial invagination into the ovarian cortex, and a transition was observed between the surface epithelium and the mucinous cyst-forming epithelium. Immunohistochemically, the stromal cells were positive for alpha-smooth muscle actin and proliferating cell nuclear antigen. Ultrastructurally, the glandular epithelium had numerous mucinous secretory granules and microvilli. The stromal cells had numerous parallel microfibrils with focal density. It is rare to encounter evidence of a transition from the surface epithelium to the mucinous tumor epithelium and to show stromal smooth muscle proliferation in a mucinous cystadenoma.     

A spontaneously occurring malignant ovarian Sertoli cell tumor in a young Sprague Dawley rat

Primary ovarian tumors are generally uncommon in rats used in toxicologic studies. A malignant Sertoli cell tumor was present in the ovary of a 19-week-old female Sprague Dawley rat. Macroscopically, the mass was white and firm, 10 × 13 × 17 mm in size, and located in the right ovary. Histopathologically, the mass was composed of nests of pleomorphic cells, which formed seminiferous-like tubules separated by a thin fibrovascular stroma. The tubules were lined by tumor cells, which had basally located nuclei and abundant eosinophilic and vacuolated cytoplasm. In some areas, the tumor cells were arranged in a retiform growth pattern, mimicking a rete testis/ovarii. Disseminated metastases to the surfaces of the mesentery, spleen and liver were also present. Immunohistochemically, many tumor cells were strongly positive for vimentin, estrogen receptor α and Ki 67. Some tumor cells were positive for pancytokeratin and inhibin α. These findings closely resemble those of an ovarian-derived human malignant Sertoli cell tumor. From our review of the literature, we believe this is the first report of a spontaneous malignant Sertoli cell tumor in the ovary of a young laboratory rat. This case might provide useful historical control information for rat toxicity studies.     

Pancreatic Ductal Adenocarcinoma in a Wistar Hannover GALAS Rat

There are no reported spontaneous cases of pancreatic ductal adenocarcinoma (PDAC), and there are few reports about chemically-induced PDAC in rats. We encountered a PDAC in a Wistar Hannover GALAS rat that had been subjected to a medium-term multiorgan carcinogenicity bioassay. This article describes the histological and histochemical findings of the tumor. The tumor was located in the pancreatic tissue and had not invaded the liver parenchyma or the mucosal layer of the alimentary tract. The tumor cells were atypical and were mainly arranged in small tubules. In addition, abundant stroma and mucus production were observed in the tumor. In an immunohistochemical examination, the tumor cells were positive for cytokeratin, Sox9 and pancreas duodenum homeobox 1 and negative for amylase 2A and insulin. Therefore, the tumor was diagnosed as a PDAC based on its histological and histochemical findings. We considered that the tumor was caused by the carcinogens administered during the abovementioned bioassay.     

Glomus tumor in the digit of a cat

A solitary mass approximately 1.5 x 2 cm located on the outer side of the third digit of the left forepaw of a 7-year-old male cross-breed cat was examined pathologically. The excised tumor mass was hard and white and located within the deep dermis and subcutis. Histopathologically, the mass consisted of a mixed population of small round epithelioid cells arranged in ribbon- or cordlike structures and spindle-shaped cells forming loose irregular bundles in a mucinous stroma. The epithelioid cells were often arranged around small blood vessels. Neoplastic cells were intensely positive for vimentin and alpha smooth muscle actin and negative for keratin, desmin, S-100 protein, and neuron-specific enolase. Based on these pathologic features, the tumor was diagnosed as a glomus tumor, a neoplasm not previously reported in cats and extremely rare in animals.     

Immunohistochemical characterization of a hepatic neuroendocrine carcinoma in a cat.

A hepatic mass was identified in a 5-year-old, female mixed-breed cat that died spontaneously after a clinical history of progressive emaciation, ptyalism, and persistent coryza. At necropsy, a 7-cm-diameter, yellow-brown, firm, multilobulated tumor was identified in the liver. Microscopically, the mass consisted of neoplastic cells arranged in small, closely packed nests within a thin fibrovascular stroma. These cells were of medium sized and polygonal, with fine argyrophilic cytoplasmic granules. Nuclei were predominantly round with finely stippled chromatin and indistinct nucleoli. Mitotic figures were numerous. Immunohistochemically, most of the neoplastic cells were immunoreactive for chromogranin A, neuron-specific enolase (NSE), and cytokeratin AE1/AE3 and weakly labeled for synaptophysin. The tumor was negative for glial fibrillary acidic protein (GFAP), vimentin, and cytokeratins 5, 6, 8, and 17. Vascular emboli and intrahepatic micrometastasis were also identified with chromogranin A. All these features were consistent with a hepatic neuroendocrine carcinoma and emphasized the importance of using a panel of antibodies to diagnose such rare tumors.     

Oleic acid-associated bronchiolitis obliterans-organizing pneumonia in beagle dogs

Accidental intra-airway exposure of dogs with pure oleic acid produced bronchiolitis obliterans and bronchopneumonia. Pulmonary changes included multifocal to coalescing necrosis of bronchioles and adjacent alveoli, hemorrhage, inflammation, and exudation of fibrin. Hyperplasia of bronchiolar and alveolar epithelial cells and proliferation of loose fibrovascular connective tissue formed polyps or plugs of variable size and shape. Polyps in the airways primarily consisted of fibroblasts with loose or myxoid stroma and were variably covered with attenuated epithelial cells. Some polyps had prominent vasculature, mixed inflammatory cell infiltration, and/or necrosis. Polyps or plugs variably effaced bronchioles and adjacent alveoli. The changes closely resembled human bronchiolitis obliterans-organizing pneumonia (BOOP). Controlled intra-airway delivery of oleic acid in dogs may be a potential animal model of obstructive pulmonary diseases such as BOOP or bronchiolitis obliterans.     

Thyroid c-cell carcinoma in an African pygmy hedgehog (Atelerix albiventris).

A 3-yr-old African pygmy hedgehog (Atelerix albiventris) was submitted with dysphagia, weight loss, and tetraparesis. A palpable mass was found on the ventral neck. Histologic examination revealed replacement of the thyroid gland by a highly cellular, expansile, and infiltrative mass composed of lobules of polygonal cells separated by fine fibrovascular septa. Examination of ultrathin sections revealed tumor cells with few to many dense-core neuroendocrine granules, approximately 100-200 nm in diameter, and stromal amyloid. Immunohistochemical stains were positive for neuron-specific enolase. Only rare cells had positive immunohistochemical staining for calcitonin. Findings are consistent with a neuroendocrine tumor of C-cell origin. This is the first report of a C-cell carcinoma in a hedgehog.     

Renal dysplasia in a pig

A diagnosis of renal dysplasia was made in a six-month-old, male, mixed-breed pig. Both kidneys were small, firm, slightly pitted, and contained an indistinct corticomedullary junction. Histologically, primitive tubules were present surrounded by an abundant loose, mesenchymatous stroma. Occasionally, tubules were markedly dilated and lined by a pseudostratified columnar epithelium forming epithelial mats that obscured the lumina. Immature glomeruli were present. Multifocal glomerular sclerosis was evident. Other mature glomeruli were enlarged and characterized by mesangial cell hyperplasia forming an arborizing pattern.