EVALUATION OF HISTOPATHOLOGICAL GRADING, MITOTIC INDEX AND KIT LABELLING PATTERNS AS PROGNOSTIC INDICATORS FOR CANINE CUTANEOUS MAST CELL TUMOURS R.F. Strefezzi * , J.G. Xavier z , S.R. Kleeb z and J.L. Cat~ ao-Dias y * Departamento de Medicina Veterin aria da Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de S~ ao Paulo, y Departamento de Patologia da Faculdade de Medicina Veterin aria e Zootecnia, Universidade de S~ ao Paulo and z Universidade Metodista de S~ ao Paulo, Brazil Introduction: Mast cell tumours (MCTs) are the most frequent skin neoplasms in dogs. Cytoplasmic KIT labelling patterns have been associated with a worse prognosis for these tumours. The aim of the present work was to compare the histopathological grading system, KIT labelling and the mitotic index (MI) as prognostic indicators for canine cutaneous MCTs. Materials and Methods: Twenty-four cases of canine cutaneous MCTs were selected. The tumours were graded by four pathologists with no clinical information about the cases according to the grading systems of Patnaik et al. (1984), Kiupel et al. (2004) and Romansik et al. (2007). Results: KIT labelling was not associated with disease-related mor- tality or survival. Survival was significantly different between histo- pathological grades. MI and survival were correlated. Best results were obtained for histopathology, followed by MI and KIT labelling patterns as prognostic indicators. Conclusions: KIT immunolabelling and the MI add information to the Patnaik grading system. However, the histopathological grading system still remains the gold standard for classification of canine cutaneous MCTs until the development of a more efficient approach. INCREASED HYPOTHALAMIC DOPAMINERGIC NEURON TYROSINE HYDROXYLASE EXPRESSION IN LEAN WISTAR RATS J. Wright * , S. Plummer y , R. Weigand z and M. Millar z * Syngenta, y Micromatrices and z MRC Centre for Reproductive Health, UK Introduction: Calorific restriction in Wistar rats has been reported to show a decrease in mammary and pituitary tumours and an in- crease in uterine tumours associated with delayed hypothalamic dopaminergic neuronal senescence. Materials and Methods: Hypothalamus from formalin-fixed and paraffin wax-embedded (FFPE) brain blocks from 12 control and 12 lean 106-week-old Wistar rats was evaluated, using a combination of immunohistochemistry (IHC), RNAscopeTMTM in-situ hybridi- zation (ISH) for tyrosine hydroxylase (TH) protein, TH dual fluores- cence IHC/ISH and microarray analysis following laser dissection. The labelling was quantified by image analysis Results: IHC labelling was observed in the tubular infundibular dopaminergic (TIDA) neurons and the axonal projections onto the median eminence (ME), with stronger labelling in the ME. TH RNA expression was detected predominantly in the TIDA neurons. Dual fluorescence, IHC/ISH, demonstrated coincident TH protein and TH RNA expression in some neuronal cell bodies and axons. The rats with reduced body weight gain showed an increase in TH RNA (TIDA) and TH protein labelling in both TIDA and ME. Mi- croarray analysis of the hypothalamus revealed down-regulation of GABA B receptor, which is known to control dopamine production. Conclusions: These results support previous observations, that chronic reduction in body weight gain may alter regulation of TH expression at the RNA and protein levels in the TIDA hypothalamic nuclei. They also demonstrate a possible GABA control mechanism CASE REPORT: A RAT HEPATIC SCHWANNOMA C.I. Teixeira-Guedes * , A.I. Faustino-Rocha * , D. Talhada * , A. Andrade * , R. Pacheco * , R.M. Gil da Costa y , J.A. Duarte z , R. Ferreira x , F. Seixas * and P.A. Oliveira * * Department of Veterinary Sciences, UTAD, Vila Real, y Faculty of Engineering, UP, Porto, z Research Centre in Physical Activity, Health and Leisure, UP, Porto and x Department of Chemistry, UA, Aveiro, Portugal Introduction: Schwannomas occur naturally in several body tissues in both man and animals, exhibiting uniform immunoreactivity for vimentin, S100 protein and neuron-specific enolase (NSE). We describe a case of a hepatic schwannoma found in a rat model of chemically-induced mammary cancer. Materials and Methods: Animal procedures were approved by the Portuguese DGAV (No. 008961). A female Sprague-Dawley rat was injected with N-methyl-N-nitrosourea (MNU) at 7 weeks of age and died spontaneously 15 weeks later. A complete necropsy examination was performed and lesions were studied histologically. Results: On necropsy examination, a haemorrhagic, multicystic, well-circumscribed hepatic mass was observed. Histologically, hepatic parenchyma was replaced by a well-circumscribed mass composed of spindle-shaped cells arranged in a wavy pattern and supported by a poorly-stained matrix. Large haemorrhagic and necrotic cystic areas were present multifocally. The lesion invaded the costal wall and the diaphragm. Tumour cells displayed occasional positivity to vimentin and diffuse reactivity with S100 and NSE markers. Conclusions: Gross and microscopical findings were compatible with the diagnosis of hepatic schwannoma, chemically-induced by MNU administration. Although infrequent, the occurrence of schwannomas has been described in other species, and different or- gans, associated with N-ethyl-N-nitrosourea and MNU exposure. (The first two authors contributed equally to this study) PAROTID ADENOCARCINOMA WITH OSTEOLYTIC ACTIVITY IN A CAT A. Calado * ,y , A. Duarte A * and J. Pego * * Faculdade de Medicina, University of Coimbra and y Escola Universit  aria Vasco da Gama, Coimbra, Portugal Introduction: A 9-year-old female Siamese cat presented with ataxia, right ear canal bleeding and head tilt to the right. Antibiotic treatment for otitis did not lead to clinical improvement. Over the period of 1 week the cat developed anorexia, tongue displacement and a right ranula and left tracheal displacement. Materials and Methods: The cat was humanely destroyed and subjected to necropsy examination. Results: In the right parotid region there was a sessile tumour. This was white in colour, lobulated, friable, markedly infiltrative and os- teolytic. The temporal and parietal bones were absent and the tumour was in contact with the brain. Several branches extended to the tongue, regional lymph nodes and surrounding soft tissues. Microscopically, the tumour and the infiltrating branches were het- erogeneous with pale cells, having an eccentric small nucleus, ar- ranged in solid shape, in addition to pleomorphic polyhedral cells with a dense nucleus arranged in a papillary pattern. There was cen- tral necrosis. Abundant spindle cells resembling myoepithelium sur- rounded the basement membranes. Normal parotid gland was noted adjacent to the tumour. Conclusions: A diagnosis of parotid adenocarcinoma was made. Salivary gland tumours are rare in cats. The osteolytic behaviour of salivary adenocarcinoma is not commonly reported and it should be included as a differential diagnosis for skull osteolytic conditions and central neurological disease. 150:1, 2014 ESVP/ECVP Proceedings 2013 113