A bronchopulmonary artery fistula in a horse.

A 24-year-old, Thoroughbred gelding presented with difficulty breathing for a few days and intermittent nose bleeding before dying. At necropsy, the bronchoesophageal artery and the bronchial artery that flowed into the left anterior lobe were tortuous and dilated, and it was found that dilated tortuous branches of the bronchial artery ran over the dorsal and ventral surfaces of the left anterior lobe. Histopathologically, an anastomosis between a muscular artery and an elastic artery were demonstrated, which were identified as bronchial and pulmonary arteries, respectively. Based on the gross and histopathological findings, a bronchopulmonary artery fistula was diagnosed. To the best of our knowledge, this is the first case report of a pulmonary vascular anastomosis in a horse.

Mediastinal basaloid carcinoma arising from thymic cysts in two dogs.

Mediastinal masses in dogs were diagnosed as basaloid carcinoma associated with multiple thymic cysts (MTCs). The masses were composed of MTCs and proliferating intracystic neoplastic basaloid cells, which immunohistochemically diffusely expressed p63 and cytokeratin 19. A gradual transition from the basal cell layers lining the cysts walls to the neoplastic cells was seen, and it was indicated that the neoplastic cells had originated from the basal cell layers of the cysts. To the best of our knowledge, this is the first report of basaloid carcinoma occurring in the mediastinal cavity in dogs. Although these tumors were demonstrated to be rare origins, basaloid carcinoma should be included in the differential diagnoses for canine mediastinal tumors.

Gross and histological lesions in the livers of sika deer with particular emphasis on fascioliasis.

We performed gross and histological examinations of the livers of sika deer (Cervus nippon yesoensis) in Hokkaido, Japan. Out of 1,381 deer slaughtered for venison production, thickening and dilation of the large intrahepatic bile ducts and Fasciola flukes in the duct lumens were detected in 621 deer (45.0%). Furthermore, 107 non-bile lesions (75 intrahepatic and 32 capsular lesions) were detected during gross examinations. Histologically, the bile duct lesions included chronic proliferative cholangitis, papillary hyperplasia, goblet cell and pyloric gland metaplasia, and periductal fibrosis. Many of the intrahepatic non-bile duct lesions (53/75, 71%) were considered to be Fasciola fluke migration-associated lesions, including two lesion types: necrosis, hemorrhage, and eosinophilic granuloma formation (29 lesions), and lymphoid tissue formation (24 lesions). Lymphoid tissue formation was considered to result from the persistent immune responses against dead Fasciola flukes. An epidermoid liver cyst was found incidentally, which has not been reported in the veterinary literature. In summary, this study demonstrated the predominance of fascioliasis-associated lesions in sika deer livers. The gross and histological lesions caused by Fasciola flukes in sika deer were similar to fascioliasis in other animals. Moreover, we described lymphoid tissue formation as a fascioliasis-associated lesion for the first time. The fact that bile duct lesions (45.0%) had a markedly higher prevalence than fascioliasis-associated parenchymal lesions (53/1,381, 3.8%) indicated that sika deer are a permissive host for fascioliasis. Our results provide information that will aid pathological examinations of sika deer.

Primary intrahepatic squamous cell carcinoma in a sika deer.

A white nodule was detected in the liver of a wild female sika deer. The nodule was histologically diagnosed as squamous cell carcinoma (SCC), and it transitioned into a hyperplastic and chronically inflamed intrahepatic bile duct showing Fasciola infection. Therefore, the tumor was demonstrated to have originated from the biliary epithelium of the intrahepatic bile duct. Hyperplastic and chronic inflammatory changes of the biliary epithelium might have contributed the carcinogenesis of the present case, as proposed in human primary intrahepatic SCC cases. To the best of our knowledge, this is the first reported case of primary intrahepatic SCC in an animal.

Peritoneal sarcomatoid mesothelioma in a sika deer.

A slaughtered 2-year-old female sika deer (Cervus nippon yesoensis) had diffusely distributed multinodular lesions on the serosal surface of the peritoneal cavity and several nodules in the pleural cavity. Histologically, they were composed of proliferating spindle-shaped neoplastic cells, arranged in a fascicular fashion. The cells in the invasive foci transitioned from a sarcomatoid to an epithelioid appearance. Immunohistochemically, both the spindle-shaped and epithelioid cells were at least focally positive for pancytokeratin, vimentin, calretinin, α-SMA, and desmin. From these findings, the deer was diagnosed with peritoneal sarcomatoid mesothelioma with metastasis to the pleural cavity. To our knowledge, this is the first reported case of peritoneal mesothelioma in a cervid species and the first case of mesothelioma in a sika deer.

Pulmonary adenofibroma in a sika deer.

A solitary firm nodule was found in the lung of a sika deer (Cervus nippon yesoensis). Histologically, it was a biphasic lesion composed of epithelial and stromal cell elements and exhibited a leaf-like growth pattern. The epithelial cells were immunohistochemically positive for pancytokeratin, cytokeratin 7, napsin A, and thyroid transcription factor-1, and the stromal cells were positive for vimentin and partially positive for desmin and α-smooth muscle actin. These observations were consistent with pulmonary adenofibroma, which is an extremely rare lesion in humans. To the best of our knowledge, this is the first reported case of pulmonary adenofibroma in an animal.

Basal cell adenocarcinoma on bulbar conjunctiva of third eyelid in a dog.

An 8-year-old castrated Toy poodle presented with swelling and proptosis of the right third eyelid caused by an exophytic mass on the bulbar surface. Histologically, the mass was composed of stratified neoplastic basaloid cells, arranged in nests and interconnecting islands, which were mixed with tubular structures. Immunohistochemically, the basaloid cells were positive for p63 and cytokeratin (CK) 14, and the inner epithelial cells of the tubular structures were positive for CK7, CK8, and CK19. According to these findings, the mass was diagnosed as a basal cell adenocarcinoma. Although basal cell adenocarcinoma is rare in animals, it should be included in the list of differential diagnoses for superficial tumors of bulbar conjunctiva of third eyelid in dogs.

Synchysis scintillans of the anterior chamber in a dog.

Intraocular cholesterol granuloma (CG) associated with synchysis scintillans (SS) was diagnosed in a 5-year-old spayed Shetland sheepdog. During the initial clinical examination, the patient exhibited SS in the anterior chamber. Canine SS is usually found in the vitreous cavity, and SS in the anterior chamber has not been described. Since canine SS has been reported to be a non-progressive condition, and its long-term clinical course has not been adequately documented. The present case report describes the long-term clinical course of a case of canine SS, in which SS occurred in the anterior chamber, leading to intraocular CG formation, and eventually glaucoma.

Blindness associated with nasal/paranasal lymphoma in a stallion.

A 29-year-old stallion presented with bilateral blindness following the chronic purulent nasal drainage. The mass occupied the right caudal nasal cavity and right paranasal sinuses including maxillary, palatine and sphenoidal sinuses, and the right-side turbinal and paranasal septal bones, and cribriform plate of ethmoid bone were destructively replaced by the mass growth. The right optic nerve was invaded and involved by the mass, and the left optic nerve and optic chiasm were compressed by the mass which was extended and invaded the skull base. Histologically, the optic nerves and optic chiasm were degenerated, and the mass was diagnosed as lymphoma which was morphologically and immunohistochemically classified as a diffuse large B-cell lymphoma. Based on these findings, the cause of the blindness in the stallion was concluded to be due to the degeneration of the optic nerves and chiasm associated with lymphoma occurring in the nasal and paranasal cavities. To the best of our knowledge, this is the first report of the equine blindness with optic nerve degeneration accompanied by lymphoma.

Characterization of equine hyalocytes: their immunohistochemical properties, morphologies and distribution.

In horse, the characterizations of hyalocytes under the steady state are still unclear. Therefore, we investigated characterizations of hyalocytes in normal equine eyes by their immunohistochemical phenotype, histomorphology and distribution. Thirty-one eyes from 18 horses, divided into 4 groups (G) by age, were used: early (G1) and late gestation (G2) fetuses, 1- to 3-year-old (G3) and 8- to 24-year-old (G4) horses. Equine hyalocytes were histologically classified into 4 types, and they immunohistochemically expressed MHC II and CD163. Hyalocytes were detected on and/or around ciliary processes and pars plana in G2, G3 and G4, but were not located on retina and optic papilla. A significant increase in distribution was found between G2 and both G3 and G4, and the largest distribution was found at ciliary processes in these groups. Equine hyalocytes were characterized as residential ocular macrophage and MHC II antigen-bearing cell, accompanied by a pleomorphic appearance and located in the contiguous ciliary body. Our data provided characterizations of hyalocytes in normal equine eyes and may well contribute to improving the understanding of pathogenesis of equine ocular disease.

Distribution of CD163-positive cell and MHC class II-positive cell in the normal equine uveal tract.

Antigen-presenting cells (APCs) in the uveal tract participate in ocular immunity including immune homeostasis and the pathogenesis of uveitis. In horses, although uveitis is the most common ocular disorder, little is known about ocular immunity, such as the distribution of APCs. In this study, we investigated the distribution of CD163-positive and MHC II-positive cells in the normal equine uveal tract using an immunofluorescence technique. Eleven eyes from 10 Thoroughbred horses aged 1 to 24 years old were used. Indirect immunofluorescence was performed using the primary antibodies CD163, MHC class II (MHC II) and CD20. To demonstrate the site of their greatest distribution, positive cells were manually counted in 3 different parts of the uveal tract (ciliary body, iris and choroid), and their average number was assessed by statistical analysis. The distribution of pleomorphic CD163- and MHC II-expressed cells was detected throughout the equine uveal tract, but no CD20-expressed cells were detected. The statistical analysis demonstrated the distribution of CD163- and MHC II-positive cells focusing on the ciliary body. These results demonstrated that the ciliary body is the largest site of their distribution in the normal equine uveal tract, and the ciliary body is considered to play important roles in uveal and/or ocular immune homeostasis. The data provided in this study will help further understanding of equine ocular immunity in the normal state and might be beneficial for understanding of mechanisms of ocular disorders, such as equine uveitis.

Systemic mycobacteriosis in an aborted thoroughbred fetus in Japan.

A male Thoroughbred fetus was aborted on day 251 of pregnancy. Gross and histological examinations detected systemic granulomatous lesions in many superficial and visceral lymph nodes and organs including the liver, tonsils, lungs, thymus, spleen, right thyroid gland and gastrointestinal tract, and suppurative placentitis, pyogranulomatous amnionitis and intralesional acid-fast bacilli were also detected. An examination of the DNA base sequence of the ß subunit of RNA polymerase demonstrated that Mycobacterium avium strain 104 had infected several organs. To the best of our knowledge, this is the first report of equine fetal mycobacterial infection in Japan.