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Histiocytic sarcoma (HS) is a haematopoietic tumour of histiocyte origin that has been sporadically reported in four-toed hedgehogs (Atelerix albiventris). The present study aimed to investigate clinical, gross, histopathological and immunohistochemical features of HS in eight hedgehogs. Histological and immunohistochemical features of normal histiocytes and Langerhans cells (LCs) of hedgehogs were also investigated. HLA-DR-, Iba-1- and E-cadherin-positive LCs were observed in the epidermis, while Iba-1- and CD204-positive histiocytes were detected in the lymph nodes and spleen of normal hedgehogs. Localized HS (six cases) developed in the skin and spleen, while disseminated HS (two cases) occurred in the intestine. Tumour cells of disseminated HS were also distributed within the mesenteric lymph nodes, liver, kidney, spleen, lung and adrenal glands. Tumour cells of both localized and disseminated HS were composed of histiocytic cells, spindle to pleomorphic cells, multinucleated giant cells and erythrophagocytic cells. Most tumour cells were immunopositive for Iba-1, CD204 and lysozyme. A small number of tumour cells were positive for E-cadherin and CD208, and the tumour cells in one case were positive for HLA-DR. These results suggest that the tumour cells have variable features of histiocyte origin, including dendritic cells, LCs and macrophages. The behaviour of HS in the hedgehog was very aggressive, and 50% of cases died within 90 days of resection. The present study also highlighted the tendency for local tumour recurrence in localized cutaneous HS cases, suggesting a requirement for a long-term follow-up after excision.

Summary Twenty-two newborn puppies that did not receive colostrum exhibited acute respiratory signs and died at a breeding facility. Pathological examinations were performed on four of the puppies. At necropsy examination, the lungs were firm and mottled dark red, consistent with acute bronchopneumonia. Histopathologically, there was marked infiltration of neutrophils and macrophages into the bronchi and alveoli, and gram-negative coccobacilli were attached diffusely to the cilia of bronchial mucosa. Immunohistochemistry for Bordetella bronchiseptica antigen revealed positive labelling of the bacterial agents. On electron microscopy, a large number of coccobacilli were observed attaching to the cilia of bronchial epithelial cells. Real-time polymerase chain reaction amplified a B. bronchiseptica gene from the affected lung tissue. Based on these findings, the four puppies were diagnosed with fatal B. bronchiseptica bronchopneumonia.

A 6-year-old intact female sugar glider (Petaurus breviceps) had a swelling at the pouch region and died 8 days after presentation. At necropsy, the urinary bladder and abdominal lymph nodes were enlarged and a mass was located in the pericloacal region. Tumour infiltration was also observed in the medial iliac lymph nodes, liver, spleen, small intestine, uterus and left ovary. Histopathologically, the tumours were composed of pleomorphic histiocytes that had round or bizarre nuclei and abundant pale eosinophilic cytoplasm. Immunohistochemically, tumour cells were positive for ionized calcium-binding adaptor molecule 1 and human leukocyte antigen and negative for CD3, B lymphocyte antigen 36 and cytokeratin. Histopathological and immunohistochemical examinations confirmed a diagnosis of disseminated histiocytic sarcoma. This neoplasm has not been previously reported in a sugar glider.

A 6-year-old female black-tailed prairie dog (Cynomys ludovicianus) was presented with a space-occupying lesion in the left submandibular region. On computed tomography, a low attenuating, poorly circumscribed mass infiltrated the left mandibular bone, with osteolytic change. Microscopically, the lesion was composed of odontogenic epithelium proliferating in nests and embedded in abundant dental papilla-like ectomesenchyme, including dentine and enamel. Multifocal amyloid deposition was observed. Immunohistochemically, the neoplastic epithelial cells were positive for cytokeratin (CK) AE1/AE3, CK14 and p63. Some epithelial cells were positive for amelogenin and some adjacent to the amyloid deposits co-expressed S100. The ectomesenchymal cells expressed vimentin and strong S100 immunoreactivity was observed in odontoblast-like cells. The amyloid was immunolabelled with amelogenin. The tumour was diagnosed as amyloid-producing odontoameloblastoma.

A 1 cm diameter mass was detected in the caudal superotemporal area of the left eye of a 6-year-old neutered male ferret (Mustela putorius furo). The mass and the left eye were removed surgically. Microscopical examination revealed a tumour of the adnexal gland of the eye that had invaded the surrounding ocular muscle. The tumour was composed of basal-type epithelial cells arranged in a solid, or occasionally tubular, pattern. Immunohistochemically, the tumour cells expressed cytokeratin and p63, but not smooth muscle actin. Based on these findings, the tumour was diagnosed as a basal cell adenocarcinoma of the lachrymal gland. In addition to the tumour, the retina of the left eye was detached and folded at the centre of the globe. This is the first report of a non-human case of basal cell adenocarcinoma of the lachrymal gland.

Stem cell factor (SCF) is a ligand of the molecule Kit, which is expressed in mast cells and is important for mast cell proliferation, migration and survival. Mast cell tumours (MCTs) are associated with mutations of c-kit, a proto-oncogene encoding the Kit protein. In this study, we examined SCF expression in 23 samples of feline MCTs. SCF expression was detected in 10 cutaneous MCTs and a case of splenic mastocytosis. In the cutaneous MCTs, SCF-positive tumour cells were located at the margins. Kit was expressed in eight of the 10 cutaneous cases of SCF-expressing MCTs. In these cases, Kit-positive cells were located near to SCF-positive cells, and SCF/Kit double-positive tumour cells were found. Ki67-positive tumour cells were not found near to SCF-positive cells. These results suggest that SCF autocrine/paracrine mechanisms are involved in the expansion of cutaneous MCTs, but not in tumour proliferation.

Trichoblastoma is the most common skin tumour in the rabbit. The aim of the present study was to characterize the histological and immunohistochemical features of trichoblastoma in 27 rabbits. Common sites of tumour occurrence were the neck (6/30, 20%), head (5/30, 16.7%), flank (4/30, 13.3%) and hindlimb (4/30, 13.3%). Histologically, rabbit trichoblastoma was categorized into ribbon (10/30, 33.3%), trabecular (8/30, 26.7%) and mixed types (12/30, 40%). The tumour tissue showed close interaction with the surrounding stroma where prominent fibroblastic aggregation, known as papillary mesenchymal bodies, was frequently observed (24/30; 80%). Peritumoural stroma of all cases was stained by Alcian blue (at pH 2.5 with weaker staining at pH 1.0). Immunohistochemically, the peripheral palisading basal-type cells of the tumour were positive for cytokeratin (CK) 14 while the inner cells were typically positive for CK17, differing from the immunohistochemical profile of the rabbit epidermis and hair follicle. The present study suggests that uncontrolled embryonic trichogenesis is involved in the development of trichoblastoma in the rabbit.

An 11-year-old female Chihuahua exhibited respiratory distress and a computed tomography scan showed a large mass in the anterior thoracic cavity. During surgery, it was found that the mass was strongly adherent to surrounding tissue. A histopathological examination of a biopsy sample from the mass revealed proliferation of atypical epithelial cells and cartilage formation admixed with mature lymphocytes. Immunohistochemically, the tumour cells, as well as the normal canine thymic epithelial cells, were positive for pan-cytokeratin (CK), CK5/6, CK19, p63 and bone morphogenetic protein (BMP) 6. Foci of cartilage tissue were formed in association with the neoplastic epithelial tissue. In the normal canine thymus, the subcapsular epithelial cells are positive for both CK19 and BMP6. These findings indicate that the cartilage element within the tumour developed from CK19-positive neoplastic epithelial cells, which were derived from the thymic subcapsular epithelium. This case represents a novel variant of canine thymic epithelial tumour that exhibits cartilage differentiation.

The OBE-1 strain of Akabane virus infects the fetus via the dam, resulting in abortion or congenital abnormalities in ruminants. In contrast, the Iriki strain of Akabane virus is highly virulent and causes encephalomyelitis by post-natal infection. To clarify the difference in pathogenicity between the two strains, BALB/cAJcl mice were inoculated either intraperitoneally or intracerebrally (IC) with either strain from 3 days to 8 weeks of age. Pathological examination revealed non-suppurative encephalitis in mice inoculated by either route with the Iriki strain. Virus antigens were distributed widely throughout the brain when the virus was inoculated into newborn mice, but distribution was limited to the brainstem in mice inoculated when 8 weeks old. However, brain lesions were observed only in mice inoculated with OBE-1 by the IC route when the mice were 3 days old, but these lesions were mild. To examine the manner of viral spreading, the Iriki strain was inoculated IC or intrastriatally into 8-week-old mice. Viral antigens were distributed prominently throughout the spinal cord as well as the brainstem and various cerebral nuclei, and were present with less prominence in the connective fibres. Virus antigens were also distributed in the subventricular zone, where neuronal stem cells exist. These results show that the neuroinvasiveness of the Iriki strain diminishes with age, while neurovirulence is maintained; however, for the OBE-1 strain both neuroinvasiveness and neurovirulence diminish with age. Furthermore, Akabane virus infects neuronal cells in the brainstem and spreads to the spinal cord via an unidentified transneuronal pathway.