Cystic cholangioma in the thoracic cavity of a rat

A female congenic rat produced by repeated backcrossing of Nihon rats, a model for hereditary renal cell carcinoma, to Brown Norway rats was necropsied at 24 months of age. At necropsy, a white mass about 1 centimeter in size was observed in the thoracic cavity, and the mass partly adhered to the esophagus and the diaphragm. Histologically, the mass was clearly circumscribed by connective tissue, and consisted of neoplastic cuboidal epithelial cells that showed cystic tubular proliferation. Some islands of well-differentiated hepatocytes and some vessels were observed in the mass. Immunohistochemically, the tumor cells were strongly positive for cytokeratin and partly positive for vimentin but were negative for mesothelin and Von Willebrand Factor. The positive rate for Ki-67 was 2.4%. Based on these histological and immunohistochemical evidences, we diagnosed this tumor as a cystic cholangioma that might have arisen from the ectopic hepatic tissue in the thoracic cavity.     

Pinealoma in a broiler breeder

An incidental central nervous system tumor was found in a broiler breeder. The cellular mass was histologically similar to the normal pineal gland, but it was characterized by a decreased ratio of follicular/parafollicular cells, a relative increase in mitoses, a size three times greater than a normal pineal gland, and growth and expansion into adjacent cerebellar tissue. These characteristics warranted a diagnosis of pinealoma rather than pineal gland hyperplasia.     

A giant parovarian cyst in a dog with a granulosa cell tumor

A 13-year old intact female poodle showed persistent signs of estrus. Ultrasonographically, a large cystic mass containing echogenic fluid with a thin wall was observed, and it was 8 cm in diameter. The cystic mass was located at the mesovarium between the left ovary and uterine horn, and it was identified as a giant parovarian cyst. A right ovarian mass was histologically diagnosed as a granulosa cell tumor. Persistent estrogen hormone secretion by the granulosa cell tumor was thought to cause a rapid increase in the size of the parovarian cyst. This rare cystic mass originated from the genital system and was differentiated from the uterus.     

Ureteral mast cell tumor in a dog

A 6-year-old, castrated male, mixed-breed dog was diagnosed with partial unilateral ureteral obstruction secondary to a ureteral mass. The ureteral mass was surgically resected, and an ureteroneocystostomy was performed. Histopathology of the ureteral mass was consistent with a poorly differentiated mast cell tumor (MCT). The patient recovered well but was euthanized 5 months postoperatively for central nervous system signs. A choroid plexus tumor was diagnosed during necropsy examination. There was no evidence of recurrence or dissemination of the ureteral MCT. Extracutaneous MCTs are rare in dogs, and primary MCT associated with the urinary tract has not previously been reported in the veterinary literature.     

IMAGING DIAGNOSIS—ENDOMETRIAL MINERALIZATION IN A DOG

A 9‐year‐old intact female mixed breed dog was presented for mammary gland tumor surgery, and preoperative radiographs showed a tubular soft tissue opacity mass with multifocal mineralization in the caudoventral abdominal cavity. Subsequent ultrasonography demonstrated uterine dilation with echogenic fluid and endometrial acoustic shadowing consistent with mineralization. Resection of mammary gland tumors and ovariohysterectomy were performed. Pyometra was diagnosed on cytologic examination of uterine fluid. Histopathology of the uterine tissue confirmed a diagnosis of cystic endometrial hyperplasia with uterine mineralization.     

MALIGNANT PERIPHERAL NERVE SHEATH TUMOR IN A CAT

A report of a cat with a cranial tumor of nerve sheath origin is presented. The cranial mass, with a cyst-like character on presentation to the referring veterinarian suggested a benign lesion, but the clinical course was rapid and indicative of central nervous system involvement. The tumor was poorly differentiated by histologic examination, but immunohistochemistry was consistent with Schwann cell origin. Features of peripheral nerve sheath tumors in cats and other species are briefly discussed.     

Ganglioglioma in the thalamus of a puppy

A solitary brain mass of a 4-month-old miniature dachshund showing seizure-like neurological signs was examined histopathologically. At necropsy a white tumor mass, replacing the thalamus, approximately 1.5 cm in diameter, was found. There was cystic space filled with yellowish pale fluid in the central area of the tumor mass. Histopathological examination revealed that the mass consisted of irregularly arranged well-differentiated neuronal and glial cells, and multifocal mineral deposits. The neuronal cells had a large clear nucleus and various amount of Nissl substances in the cytoplasm. Some neural cells were bi-nucleated. Neither mitotic figures nor proliferating cell nuclear antigen (PCNA)-positive nuclei was found in the neuronal cells. Immunostaining for glial fibrillary acidic protein (GFAP) revealed diffuse proliferation of GFAP-positive glial cells and their processes, while these glial cells did not show apparent cellular atypism, mitotic activity, or PCNA-immunoreactivity. Accordingly, the present tumor was diagnosed as ganglioglioma, and hamartomatous histogenesis might be possible.     

Monophasic Teratoma of the Ovarian Remnant in a Bitch

An exploratory laparotomy on a mixed‐breed bitch of an estimated age of 5 years revealed that she had undergone ovariectomy in the past, but a cystic structure was present in the area of the right ovary and a whitish mass, approximately 3 cm in diameter, in the area of the left ovary. These structures were removed together with an apparently normal uterus. Histological examination of the cyst showed a thin layer of connective tissue, while the left ovarian mass revealed ovarian tissue and highly differentiated nervous tissue, confirmed through immunohistochemistry. A presumptive diagnosis of mature ovarian teratoma was made. Although teratomas generally contain recognizable elements from more than one of the three germ cell layers, they can also be monophasic, when there is only one germ layer component. Ovarian teratomas are rare in the dog and never before have been reported in an ovarian fragment.     

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.     

Functional cystic thyroid adenoma in a cat

A 9-year-old cat with hyperthyroidism was referred for radioactive iodine treatment. The cat also had a ventral cervical mass that the owners reported had been present for several years and had increased in size during the past few weeks. On physical examination, the mass was found to have caused lateral displacement of the trachea, esophagus, jugular vein, and common carotid artery. The mass was aspirated and was determined to be cystic in nature. Concentrations of thyroid hormones in the cystic fluid were similar to serum concentrations, and nuclear scintigraphy revealed thyroactive tissue lining the cyst wall. Magnetic resonance imaging suggested that the cyst originated from the right lobe of the thyroid gland. The cat was treated with sodium iodide I 131 but died 4 days later, presumably as a result of aspiration of gastric or esophageal contents. A necropsy was not performed, but histologic examination of a biopsy specimen of the mass indicated that it was a cystic thyroid adenoma.     

Oropharyngeal teratoma in a neonatal sable antelope (Hippotragus niger)

A neonatal male sable antelope (Hippotragus niger) was found dead. A 5 by 12-cm lobulated mass was present in the oral cavity, attached to the caudal border of the soft palate; this mass contained hair, cartilage, bone, nervous tissue, muscle, and multiple gland-like structures. Histopathologic diagnosis was consistent with oropharyngeal teratoma. As a result of the lack of wear of the fetal hooves, the firm, collapsed appearance of the lungs, and the lack of other gross or histopathologic abnormalities, the oropharyngeal tumor is suspected to have caused an airway obstruction, resulting in the calf's early postnatal death. This is the first report of an oropharyngeal teratoma in the veterinary literature.     

Lenticular invasion by a ciliary body adenocarcinoma in a dog

Ciliary body adenocarcinomas are well-recognized tumors in dogs; however, invasion of the lens by the tumor has not been described in veterinary species. Evaluation of the right eye of a 10-year-old Labrador Retriever revealed a ciliary body mass spanning from the 10 o'clock to 2 o'clock position that was impinging on the lens. Histologic evaluation of the enucleated eye revealed a ciliary body adenocarcinoma with lens invasion. Where the tumor encroached on the lens, the lens capsule was absent and there was scrolling of the broken ends of the capsule. Tumor cells were juxtaposed to the lens fibers and dissecting between the lens fibers. There were no inflammatory cells within the lens associated with the breaks in the capsule or within the anterior chamber. To our knowledge this is the first report of lens invasion by a tumor in any veterinary species.     

Thymoma in a dog with a part of granular cell proliferation and concurrent lymphoma cells

A 12-year-old male Shiba dog showed anemia and the swelling of systemic lymph nodes. X-ray and post mortal examinations revealed a anterior mediastinal mass. Histologically, the tumor mass consisted of four different elements; cord-like proliferation of cuboidal epithelial cells, tubular or cystic structures lined with ciliated epithelial cells, proliferation of large round-shaped epithelial cells with PAS-slightly positive granular cytoplasm, and diffuse proliferation of neoplastic lymphocytes. Epithelial cells in cord-like or cystic structures were strongly positive for cytokeratin. Granular or foamy cells were negative for all markers examined and had myelin-like bodies in the cytoplasm by electron microscopy. The neoplastic lymphocytes in the tumor mass were considered being derived from concurrent multicentric lymphoma. Based on these findings, the present case was diagnosed as thymoma with a part of granular cell proliferation and concurrent lymphoma cells.     

Acute hindlimb paresis caused by extension of a peripheral nerve sheath tumour into the spinal canal of a horse

A 10-year-old Quarter Horse gelding presented for a large, slowly growing mass in the right thoracic region caudal to the withers (approximately at the level of thoracic vertebrae 10 to 16). The mass was surgically removed, the horse returned to normal riding activity, and no external regrowth was observed. Two years after surgery, the horse developed progressive signs of hindlimb weakness, ataxia and adopting a dog-sitting stance. Post-mortem examination confirmed spinal canal infiltration and spinal cord compression (at the level of the 12th thoracic vertebra) by a similar soft tissue sarcoma as diagnosed previously. Immunohistochemistry confirmed the tumour as a peripheral nerve sheath tumour (PNST) likely originating from the twelfth thoracic spinal nerve. This report demonstrates that with incomplete tumour resection, local recurrence and extension of a PNST into the central nervous system can occur even years after initial tumour removal. Immunohistochemistry to differentiate the type of soft tissue sarcoma in cases with close association to the nervous system may prove beneficial to anticipate this uncommon complication. Early surgical resection with adjunctive therapies should be considered in these cases.     

A huge ovarian cyst in a hysterectomized bitch

A 11-year-old, spayed, female mixed breed-dog was presented with an abdominal mass that was detected 1 month ago. Upon abdominal palpation a large, firm, oval shaped, movable mass was found in the mid-abdominal region. Survey radiograph of the abdomen demonstrated an oval soft tissue dense mass located on the right side of the abdominal cavity. A large, heteregenous and cystic mass with solid components occupying the majority of the abdomen and a small, cystic mass with solid components caudal to the left kidney were identified by transabdominal ultrasonography. Computed tomography scans revealed bilateral ovarian masses, and a small volume of retroperitoneal fluid on the right side. A cystic, but otherwise solid mass located in the right ovary and small retained left ovary encapsulated in the ovarian bursa were excised surgically by midline laparotomy. Histopathological examination of the excised mass from the right side revealed a large cystic structure consistent with an ovarian cyst and multiple corpora lutea and follicles at different maturational stages were detected in the left ovary. The precise origin of the ovarian cyst could not be determined by morphological appearance. Immunohistochemical staining suggested a cyst of surface epithelial origin. At re-examination 6 months after the surgery, the bitch appeared healthy and the clinical findings were all normal. To our knowledge, the cyst described here is the largest reported in an incompletely ovariohysterectomized bitch.     

Caudal mediastinal thyroglossal duct cyst in a cat

An eight-year-old domestic shorthair cat was evaluated because of dyspnoea secondary to pleural effusion. Ultrasound examination identified a large anechoic cyst-like structure in the caudal thorax. A median sternotomy was performed, and the cystic mass was removed. Microscopically, the excised tissue was identified as a multilocular thyroglossal duct cyst with ectopic thyroid tissue. To the authors' knowledge, this is the first report of a mediastinal thyroglossal duct cyst in a cat. Despite the rarity of this lesion, it should be considered when a cystic thoracic structure is identified on thoracic ultrasound. Surgical excision of the cyst resulted in complete resolution of the pleural effusion and clinical signs.     

Cervical teratoma in a dog

A young adult boxer dog was examined for a painless swelling in the left cranial cervical area that was refractory to antibiotic therapy. Ultrasound examination revealed a hypoechoic mass abutting the rostrolateral aspect of the left mandibular salivary gland. The cystic mass was excised and was found to extend through the capsule of the salivary gland and appeared to be confluent with the glandular tissue at this point. Histopathological examination of the excised tissue demonstrated tissue from all 3 germinal layers. There was no indication of malignancy and the mass was diagnosed as a benign cervical teratoma. Hypotheses regarding the origin of teratomas in general are discussed and the origin of the teratoma in this case is suggested.     

Actinomycosis of the brain and temporal bone in a goat

A goat with neurologic signs had multifocal abscesses containing sulfur granules in the right brain and temporal bone. Histologically, the lesions consisted of pyogranulomas with several radiating bacterial colonies of various sizes. A tangled mass of filamentous and gram-positive bacteria was recognized in the central part of the colony. Actinomyces naeslundii antigen was detected in the colonies of bacteria in the brain and neighboring bone tissue by immunohistochemistry. Actinomycosis involving the central nervous system (CNS) and temporal bone is rare in animals. Cerebral infection with A. naeslundii may have resulted from direct extension from cervicofacial regions because the CNS lesions were distributed asymmetrically and were continuous with the right temporal bone.     

Sarcocystis encephalitis in a cockatiel

A sporozoan organism was considered to be the causative agent of central nervous system disease in a cockatiel. The ultrastructural characteristics were typical of the coccidian group Apicomplexa, and the fact that organisms were free within the cytoplasm of infected cells and not within a vacuole, indicated they were Sarcocystis. Light and electron microscopic evaluation of brain tissue demonstrated protozoal organisms associated with areas of necrosis. Differential diagnosis of central nervous system disease in pet birds should include protozoal encephalitis.     

Multiple cystic intestinal duplications in a cat

A 7-year-old, female European shorthair cat with a history of recurrent vomiting had a 2-cm cystic mass in the midjejunum. Cross-sectioning and histology revealed 3 separate cystic structures in the muscular layer, in addition to a regularly structured intestinal lumen. One cyst had a 3-layered wall consisting of a dysplastic mucosa, a regularly structured submucosa, and partly double-layered muscularis that sporadically contained neurons resembling a myenteric plexus. The remaining 2 cysts had similar structures except for granulation tissue lining the lumen. The lesion was diagnosed as multiple cystic duplications in the midjejunum, which is unknown to the veterinary literature to date.