Amyloid-producing Odontoameloblastoma in a Black-tailed Prairie Dog (Cynomys ludovicianus).

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.

Anti-tumour efficacy of etoposide alone and in combination with piroxicam against canine osteosarcoma in a xenograft model.

Osteosarcoma (OSA) in dogs is locally invasive and highly malignant. Distant metastasis is the most common cause of death. To date, the survival rate in dogs with OSA remains poor. The cytotoxic effects of etoposide against canine OSA cell lines, either alone or in combination with piroxicam, have been previously demonstrated in vitro. The aim of this study was to evaluate the anti-tumour effect of etoposide alone and in combination with piroxicam on canine OSA using murine models. Etoposide single agent treatment significantly delayed tumour progression with a marked reduction in Ki-67 immunoreactivity in tumour tissue. Concomitant treatment with piroxicam did not enhance the anti-tumour efficacy of etoposide. Etoposide single agent treatment and combination treatment with piroxicam down-regulated survivin expression, but was not followed by increased apoptotic activity. These findings indicate that etoposide might be a promising novel therapeutic for canine OSA. Further investigations into its potential for clinical application in veterinary oncology are warranted.

Histopathological and Immunohistochemical Study of Trichoblastoma in the Rabbit.

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.