Growth and morphological characteristics of canine venereal tumor cells in vitro

Canine venereal tumor cells were grown in monolayer and tumor tissue fragments were maintained in vitro for 56 days in medium-199. Attachment and cell replication were evident within 17 hours and monolayer was obtained by the tenth day. Growth at first comprised mainly round cells with abundance of cytoplasm and vesicular nuclei, and a few spindle-shaped cells. Later cells became more elongated and like fibroblasts. Cell degeneration started by the 17th day and most were degenerated by the 24th day. Necrosis and depletion of cell population were prominent in tumor explants during the first 2 weeks. Distinct cell multiplication was evident by the 21st day and tumor fragments were repopulated with cells resembling the original tumor by the 56th day. Two distinct morphological cell types were seen: small cells with vesicular, round to oval nuclei and acidophilic cytoplasm; and the large cells with large hyperchromatic nuclei and acidophilic cytoplasm.     

Lesions of bone and bone marrow in myeloid leukosis occurring naturally in adult broiler breeders

Lesions of bone and bone marrow in myeloid leukosis (ML) occurring naturally in adult broiler breeders were investigated pathologically. During gross examination, nodules and protrusions were commonly observed on the surface of the sternum, ribs, vertebrae, and synsacrum. The bone marrow of all the bones of the body was pale in color. Histologically, granulated myelocytes proliferated in the bone marrow of various bones and in the periosteum of the sternum, ribs, vertebrae, and synsacrum. The first proliferation of tumor cells occurred in the bone marrow of epiphysis. The myelocytes invaded through haversian and Volkmann's canals from the bone marrow to periosteal areas. Hematopoiesis was suppressed by marked proliferation of tumor cells in the bone marrow of the whole bone. Atrophy was also seen in the bones, including medullary bones of the chickens suffering from ML. Proliferation of myelocytes was seen in the bone marrow and periosteum of ossified cartilaginous rings of the trachea and larynx. Marked proliferation of myelocytes was seen in the dura mater of spinal cords, and it subsequently depressed the spinal cords. Bone formation with cartilage was seen in the periosteum of the sternum having marked proliferation of myelocytes in the bone marrow and periosteum. Ultrastructurally, tumor cells showed large nuclei and cytoplasm with large round electron-dense lysosomes. The virus particles were rarely detected in the cytoplasm of tumor cells. The polymerase chain reaction test of tumor samples showed positive for subgroup J avian leukosis virus. This study indicates that the myelocytes can invade through the compact bones to the periosteum in the sternum, ribs, vertebrae, synsarcum, and ossified cartilage of trachea and larynx having thinner compact bones. In addition, the periosteal osteogenesis with cartilage in the sternum may be reactive change against the bone atrophy because of the marked proliferation of myelocytes.     

Round cell variant of myxoid liposarcoma in a Japanese Macaque (Macaca fuscata)

A 5-year-old, female, Japanese Macaque (Macaca fuscata) was diagnosed with round cell variant of myxoid liposarcoma. At necropsy, multifocal to coalescing, reddish tan to white nodules, ranging from 0.5 to 1 cm in diameter, were noted throughout the omentum and retroperitoneum. Similar neoplastic nodules were also present in diaphragm, abdominal wall, and on hepatic capsule. Microscopically, neoplastic masses consisted of round to polyhedral cells, which had round, often eccentric nuclei and abundant eosinophilic granular and microvacuolated cytoplasm; Oil red O staining demonstrated large numbers of lipid droplets in the cytoplasm. Ultrastructurally, the cytoplasm of the tumor cells was packed with occasional lipid vacuoles and numerous enlarged mitochondria. Immunohistochemistry revealed tumor cells were positive for vimentin, while negative to cytokeratin, actin, and Factor VIII-related antigen. To the authors' knowledge, this is the first report of round-cell variant of myxoid liposarcoma in nonhuman primate.     

A spontaneous thymic carcinosarcoma in a young Sprague Dawley rat

We encountered a case of spontaneous thymic carcinosarcoma in a young Crl:CD (Sprague Dawley) rat. Grossly, a white multinodular mass replaced the thymus in the thoracic cavity. Histologically, multiple nodules were separated by fibrous stroma, and each nodule included isolated regions that were composed of epithelial or non-epithelial tumor cells. The epithelial tumor cells were relatively large and round to polygonal cells with large nuclei and weakly eosinophilic cytoplasm. These cells were cytokeratin-positive and vimentin-negative. These cells infiltrated the lungs. The non-epithelial tumor cells were poorly differentiated, small, round to spindle-shaped cells with small nuclei and basophilic cytoplasm. These cells were vimentin-positive and mostly cytokeratin-negative. Many islands of cartilage were observed near non-epithelial cells. Based on these findings, the tumor was diagnosed as a primary thymic carcinosarcoma consisting of a malignant thymoma composed of epithelial tumor cells and a mesenchymal chondrosarcoma composed of non-epithelial tumor cells.     

Spontaneous Subcutaneous Sarcoma in a 50-week-old Male Wistar Hannover GALAS Rat

A subcutaneous mass was noted in the abdomen of a 50-week-old male Wistar Hannover GALAS rat. Histologically, the tumor was composed of vimentin-positive small round cells with scant cytoplasm arranged in a trabecular, sheet or pericytoma-like pattern and spindle cells arranged in a bundle pattern and vimentin-negative round cells proliferating in an island-shaped pattern. Argentophilic thin fibers were observed to wrap up the individual cells, and some of the tumor cells showed coexpression of vimentin and cytokeratin that formed juxtanuclear globes in the cytoplasm by double immunohistostaining. Transmission electron microscopy did not reveal any characteristic features suggesting cellular differention toward a specific cell type. Based on these findings, it was difficult to specify the origin, and the tumor was diagnosed as a poorly differentiated mesenchymal tumor and classified as a sarcoma, NOS (not otherwise specified).     

Cytologic and immunohistochemical characterization of a lung carcinoid in a dog

An 11-year-old neutered male Yorkshire Terrier was presented to the Haemaru Referral Animal Hospital with a history of unresponsive tracheal collapse and an incidental finding of a lung nodule in the left caudal lung lobe on radiography. Thorough physical examination and imaging studies revealed no other masses. Cytologic examination of C-arm mobile fluoroscopy-guided fine-needle aspirates revealed numerous free nuclei and a low number of small round cells with moderate to abundant pale basophilic cytoplasm. Some cells contained indistinct basophilic granules in their cytoplasm, and extracellular pink material was noted. A caudal lung lobectomy was performed, and histologic evaluation of the mass revealed round to polygonal cells with abundant eosinophilic granular cytoplasm and round nuclei with mild anisokaryosis and 0-3 mitotic figures per high-power field. Cells were arranged in packets separated by fine fibrovascular stroma, suggestive of a pulmonary neuroendocrine neoplasm, specifically a carcinoma/carcinoid. The cells were immunoreactive for chromogranin A and neuron-specific enolase, and negative for cytokeratin, synaptophysin, calcitonin, thyroglobulin, parathyroid hormone, CD79a, light lambda, and vimentin. With these findings the tumor was diagnosed as a primary lung carcinoid. Eleven months after resection, there was no evidence of tumor regrowth or metastasis. The absence of necrosis, few mitotic figures, minimal pleomorphism, and benign behavior of this tumor resembled those of a typical carcinoid in humans.     

Granular cell variants in a rat schwannoma. Evidence of neurogenic origin of granular cell tumor (myoblastoma).

A large, intraabdominal rat schwannoma had numerous granule-containing cells cytologically identical to cells of granular cell tumor (myoblastoma). The small eosinophilic granules stained positively by the periodic acid-Schiff (PAS) reaction, with intensity not reduced by diastase pretreatment. Granules stained positively with the Tibor Pap silver impregnation for reticulin and by electron microscopy were identical to myoblastoma cell granules. The nuclei of granular cells were morphologically identical to those of the neoplastic Schwann cells. The granular cells were in numerous foci within the tumor, frequently were seen in mitosis, and possessed an extremely variable volume of cytoplasm. They seemed to evolve from neoplastic Schwann cells. Cells with only a narrow perinuclear rim of granular cytoplasm were of the same size and general configuration as adjacent neoplastic Schwann cells, while cells with increasing volumes of granular cytoplasm were increasingly swollen and round. One area of the tumor was composed almost entirely of such large cells and was histologically identical to classic granular cell tumor.     

Chromatophoroma in a crevice kelpfish (Gibbonsia montereyensis)

A captive adult crevice kelpfish, Gibbonsia montereyensis, developed a cutaneous mass, approximately 9 × 7 mm on the right side of the head in an area of nonscaled skin. Following surgical debulking, examination of both impression smears and histologic sections of the tumor revealed a predominant population of round to spindloid to polygonal cells with a moderate amount of lightly basophilic cytoplasm. The cytoplasm was filled with round, variably-sized reddish-brown granules that often obscured the nucleus. Nuclei were round to ovoid with coarsely granular chromatin. There was minimal anisocytosis and anisokaryosis. The cytoplasmic granules in histologic sections were weakly positive by the Fontana-Masson method, and staining was eliminated with melanin bleach. Immunohistochemical staining was strongly positive with a murine monoclonal antibody for melan A. As the specificity of melan A for melanophores is not clearly defined in nonmammalian species, the tumor was examined by transmission electron microscopy. Melanophores were not detected. Instead, neoplastic cells were filled with numerous intracytoplasmic organelles with triple-limiting membranes composed of concentric lamellae; these structures were most compatible with pterinosomes, which are the pigment-containing organelles of cells called xanthophores and erythrophores. As both of these organelles are ultrastructurally indistinguishable and as kelpfish skin is known to contain both xanthophores and erythrophores, a diagnosis of a mixed pigment cell tumor or chromatophoroma was made. As the tumor was grossly reddish-brown, the possibility of a neoplastic population of only erythrophores could not be excluded. Pigment cell tumors, arising from cells of the embryonic neural crest, are common in reptiles and bony fish.     

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.     

A Case of Spontaneous Malignant Hibernoma in a Crl:CD(SD)IGS Rat

A firm, tan, well-circumscribed mass that measured 25 × 30 × 35 mm was observed in the thoracic cavity of a 53-week-old male Crl:CD(SD) IGS rat. Histologically, the mass was encapsulated by fibrous tissue and contained fibrovascular septae. Tumor cells were compactly arranged, and most were oval to polygonal in shape with multivacuolated cytoplasm and a centrally located nucleus. In some parts of the tumor, marked cellular atypia and frequent mitoses were evident. Vacuoles in cytoplasm were positive for oil red O. The tumor cells were characterized ultrastructurally by abundant, round to oval mitochondria with transverse closely-packed cristae. Tumor cells were immunohistochemically positive for uncoupling protein 1 (UCP-1). Several thrombi and hemorrhagic or necrotic foci were also observed within the tumor mass. Vascular invasion of the tumor capsule was observed; however, invasion of surrounding tissues or metastases were not observed. Based on the pathology findings, this case was diagnosed as a malignant hibernoma.     

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 well-differentiated pancreatic islet cell carcinoma with vascular invasion in a male F344 rat

This case report describes a case of spontaneous pancreatic islet cell carcinoma with vascular invasion in a 110-week-old male F344 rat. Histologically, a pancreatic nodule consisting of tumor cells and many blood-rich vessels, and covered with a fibrous capsule showed local invasion in the capsule and adjacent acinar tissues, encircling a large duct-like structure (DS). The tumor was composed of well-differentiated tumor cells resembling normal pancreatic islet cells, which had small round nuclei and eosinophilic cytoplasm. Mitotic figures were rare. Immunohistochemistry revealed that the tumor cells were positive for insulin. Although endothelial cells were not detected, the DS wall showed cells positive for α-smooth muscle actin and elastic fibers, suggesting that the DS is the pancreatic artery. This is a rare case of islet cell carcinoma consisting of well-differentiated tumor cells with invasion of the pancreatic artery in a rat.     

Histopathological and Immunohistochemical Characterization of Spontaneously Occurring Uterine Deciduomas in Young Adult Rats

Uterine deciduomas were found in two female virgin rats, a 15-week-old Lewis rat and a 7-week-old Sprague-Dawley rat. The firm white nodules were located at the base of unilateral uterine horns and were approximately 6 mm and 4 mm in diameter. Histopathologically, the nodules were composed of three areas, each with a distinct type of proliferating cells: large epithelioid decidual cells with round nuclei, prominent nucleoli and abundant eosinophilic cytoplasm (antimesometrial region); compact spindle-shaped cells with oval nuclei and vacuolar cytoplasm (transitional region); and pleomorphic and spiny cells with round to oval nuclei and compact eosinophilic cytoplasm (mesometrial region). These cells proliferated in sheet-like arrangements and transformed into the other types of cells located in surrounding regions. Immunohistochemically, proliferating cells in all regions were strongly positive for proliferating cell nuclear antigen. The proliferating cells were positive for vimentin, and large decidual cells were positive for common acute lymphoblastic leukemia antigen 10, a marker of uterine interstitial cells. Large decidual cells were positive for α-smooth muscle actin and desmin, suggesting differentiation into muscular cells. Progesterone receptor was expressed in all cell types; however, estrogen receptor α was not expressed in the antimesometrial region. These extremely rare tumor-like nodules represent nonneoplastic lesions referred as decidual reactions of endometrial interstitial cells, and their biological behavior is that of a space-occupying benign tumor in young rats. Our cases might provide information as a historical control in toxicity and pharmacological studies in rats.     

Cerebral neuroblastoma and pituitary adenocarcinoma in two budgerigars (Melopsittacus undulatus)

Case 1: A tumor mass involving the rostral part of left cerebrum was found in a two-year-old female budgerigar (Melopsittacus undulatus) at necropsy. Histologically, the neoplastic cells were arranged in sheets or cords and occasionally showed nest growth patterns. These uniform tumor cells had a little cytoplasm and ovoid or round basophilic nuclei with clearly distinct cytoplasmic membranes. The tumor cells were strong diffusely immunostained with both neuron-specific enolase (NSE) and neurofilament protein and partially for synaptophysin. They lacked chromogranin A, glial fibrillary acidic protein (GFAP), vimentin, S-100, and cytokeratin antigen expression. Moreover, they had no reaction to antibodies against pituitary hormones, such as adrenocorticotrophic hormone (ACTH), growth hormone, and prolactin. The histological and immunohistochemical examination determined the tumor as neuroblastoma. Case 2: An extremely enlarged pituitary mass was found above the sella turcica of a male budgerigar. It was soft and well delineated from the adjacent structures. On histological examination, this tumor consisted of a sheet of large closely packed polyhedral cells that had scant to a large amount of pale to strongly eosinophilic cytoplasm. The pleomorphic nuclei were apparently variable in shape, from small round hyperchromatic to very large vesicular forms. The cell boundaries were not clearly distinct. The multifocal immunolabelling of neoplastic cells for NSE, synaptophysin, GFAP, and ACTH appeared, whereas a few cells reacted with vimentin and S-100 and stained negative for other markers, which were also utilized for case 1. Histological and immunohistochemical findings led to identification of corticotroph adenocarcinoma in the pituitary gland.     

Extra-adrenal pheochromocytoma (paraganglioma) in a cat

Extra-adrenal pheochromocytoma (paraganglioma) arising from periadrenal tissue was diagnosed in an 18-year-old spayed domestic shorthair cat. The tumor was palpable on physical examination, but not apparent on plain radiographs. The cat developed temporary cardiac arrhythmia while the mass was being handled during excision, suggesting that the tumor was functional. The tumor was characterized histologically by nests and sheets of neoplastic cells separated by thin, vascular stroma. The cells had abundant eosinophilic granular cytoplasm and prominent nuclei. Diffuse, dark, intracytoplasmic granules were seen in sections stained with Grimelius stain. Ultrastructurally, the cells contained round and oblong, membrane-limited, dense core neurosecretory-type granules. Serotonin was detected in the cytoplasm of the neoplastic cells by use of immunocytochemical analysis.     

Epididymal interstitial (Leydig) cell tumors in B6C3F1 mice

Six primary interstitial cell tumors of the epididymis were identified from 46,752 male B6C3F1 mice used in chronic toxicity and carcinogenicity studies. Five of the tumors occurred at the end of 2-year studies; none were attributed to treatment. None of the mice with epididymal tumors had a primary testicular tumor. Histologically, tumors were characterized by a nodular or diffuse proliferation of tumor cells in the epididymal interstitium. Most cells were polygonal with highly vacuolated cytoplasm (vacuolated cells) or eosinophilic cytoplasm (eosinophilic cells). Smaller hyperchromatic cells with scant basophilic cytoplasm (basophilic cells) and cells with yellow-brown pigment characteristic of lipofuscin (pigmented cells) were less common. In each tumor two or more cell types were present. Extension of these tumors through the capsule, invasion of the testis, or metastasis did not occur. By electron microscopy both eosinophilic and vacuolated cell types had a large round or oval nucleus with sparse heterochromatin, abundant mitochondria with tubulovesicular cristae, and frequent desmosome structures between cell membranes. Vacuolated cells contained numerous lipid droplets. Morphological features of the epididymal tumors are similar to those of the testicular interstitial (Leydig) cell tumor in mice and rats.     

Olfactory neuroblastoma in a horse

An 11-year-old thoroughbred gelding was euthanatized because of right nasal cavity tumor. The tumor consisted of round to oval cells with a scanty cytoplasm and hyperchromatic nuclei. Homer-Wright rosettes and pseudorosettes, as well as microcysts were seen. Neoplastic cells were immunoreactive to vimentin, S-100 protein, and neuron-specific enolase, glial fibrillary acidic protein and microtube-associated protein in varying degrees, indicating neurogenic nature. Based on these findings, this tumor was diagnosed as an olfactory neuroblastoma. Since this type is an uncommon tumor showing histological variety, the nature is discussed.     

Cytologic, histologic, and immunohistochemical features of lingual liposarcoma in a dog

A 9-year-old female spayed mixed-breed dog was presented to the referring veterinarian with a history of decreased appetite and difficulty with prehension and swallowing because of a firm oval mass in the tongue. On cytologic evaluation of a fine-needle aspirate of the mass there were numerous round to polygonal cells organized individually or in loose clusters with rare branching capillaries. The cells had eosinophilic granular cytoplasm, round to oval nuclei, and occasionally indistinct borders. The cytologic diagnosis was granular cell tumor (GCT) of the tongue. Impression smears of a biopsy sample of the lingual mass contained similar eosinophilic granular cells with variable numbers of clear vacuoles in the background, numerous perivascular arrangements, and occasional lipoblasts, suggestive of liposarcoma. On histologic examination the tumor was composed of numerous lipocytes with rare foci of round eosinophilic granular cells without evidence of vacuolation; occasionally, atypical mitotic figures were seen. Immunohistochemically, the cells were uniformly negative for periodic acid-Schiff and did not express smooth muscle actin, desmin, or cytokeratin but were immunoreactive for vimentin and S100. A diagnosis of well-differentiated liposarcoma was made on the basis of morphologic and immunohistochemical results. Eosinophilic granular cells may be a component of well-differentiated liposarcoma and are not limited to GCT. Liposarcoma should be considered in the differential diagnoses of lingual tumors in the dog when cytological evaluation reveals eosinophilic granular cells consistent with GCT.     

Well-differentiated biphasic synovial sarcoma in the atlanto-occipital joint of a Holstein cow

A 7-year-old Holstein cow developed a large cystic mass in the region between the atlantoaxis and larynx. The mass extended to the synovium in the atlanto-occipital joint. Many villous projections were present on the inner surface of the tumor tissue, and irregular clefts were formed in the inside. Two cell types, epithelioid-like synovioblasts and spindle cells, were present. Immunohistochemical analysis showed that the cells stained positively for cytokeratin (AE1/AE3) and vimentin. Both cells had similar fine structures ultra-structurally. Vacuoles present in the cytoplasm were full of an acid mucous substance. The tumor was diagnosed as a well-differentiated biphasic synovial sarcoma. This is the first report of a rare case of synovial sarcoma, from the viewpoint of its origin.     

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.