Nonocular melanocytic neoplasia is considered uncommon in cats yet is routinely encountered in diagnostic pathology and recognized to exhibit a wide variation in biological behavior. Accurate prediction of clinical outcomes is challenging with no widely recognized prognostic criteria. Signalment and tumor location were retrospectively evaluated in 324 cats diagnosed with nonocular melanocytic neoplasia. Histologic features were described in 141 neoplasms and outcome data were available in 79 cases. Immunohistochemistry using Melan-A, PNL-2, cyclooxygenase 2 (COX-2), and E-cadherin was performed in a subset ( n = 24). Multivariate analysis identified tumor site, mitotic count, and the presence of intratumoral necrosis to be independent predictors of tumor-related death. On the basis of these findings, we propose a novel histologic grading scheme in which nonocular melanocytic neoplasms involving the lips, oral or nasal mucosa, or nasal planum are considered high grade if they fulfill 1 or both of the following criteria: at least 4 mitoses in 10 high-power fields (HPF) or presence of intratumoral necrosis; those arising elsewhere are considered high grade if they fulfill both of the above criteria. Of 79 tumors with outcome data, 43 (54%) were low grade and 36 (46%) were high grade. The grading system had an 80% sensitivity and 92% specificity for predicting tumor-related death in this population of cats. Median survival for cats with low-grade tumors was not reached, and the median survival was 90 days for those with a high-grade tumor. PNL-2 and Melan-A were sensitive markers for feline nonocular melanocytic neoplasia, and although not significantly associated with prognosis, a large proportion expressed COX-2, suggesting a potential therapeutic role for COX-2 inhibitors.

Pathobiology and Population Sciences, The Royal Veterinary College, Hatfield, Herts AL9 7TA, UK 1 Corresponding author email: cebp3@cam.ac.uk Objectives: To identify the incidence, risk factors and presenting signs of lymphoma in dogs presenting to primary-care practice in the UK using analysis of data within the VetCompass™ programme. Materials and MethOds: Case records from the VetCompass™ programme from primary-care practices in the UK were searched for newly diagnosed lymphoma in dogs within a 1-year period: 2013. Diagnosis was based on clinical records with or without laboratory confirmation. Signalment was evaluated as risk factors for lymphoma diagnosis using multivariable logistic regression.results: There were 286 presumed newly diagnosed cases identified during 2013 from 455,553 dogs (overall incidence risk 63 of 100,000 dogs per year) of which 193 (67%) were laboratory confirmed (42 of 100,000 dogs per year). Advanced age, dogs older than 12 years, dogs weighing more than 30 kg and some specific breeds were significantly associated with lymphoma diagnosis. Only 18 dogs (6%) of the population identified were referred to a specialist clinic.clinical significance: This study concurs with others that age, bodyweight and breed are significant risk factors for lymphoma. Results of this study highlight: (1) the low number of dogs with lymphoma that are referred to specialists in the UK and (2) that few dogs undergo immunophenotyping (which can carry prognostic importance), emphasising the importance of epidemiological programmes that evaluate diseases presented to primary-care veterinarians.

Objectives To integrate external data sources with VetCompass postcode data to explore the spatial distribution and examine potential associations with environmental risk factors in dogs diagnosed with lymphoma at primary care veterinary practices. Materials and Methods Cases of lymphoma were identified from electronic patient records of 455,553 dogs under primary veterinary care during 2013 in the UK. Cases were defined as either laboratory‐confirmed or non‐laboratory‐confirmed. Disease maps at the postcode‐district level were used to define the geographic distribution of lymphoma incidence and spatial clustering was explored. Environmental risk factors from external data sources were transferred to a compatible format and logistic regression modelling was used to examine associations between environmental herbicide, fungicide and radon concentrations with lymphoma. Results From the denominator population of 455,553 dogs, 279 lymphoma cases (187 with laboratory confirmation and 93 without) were identified. Heterogeneous geographic variation was observed with weak evidence of clustering around London and the south‐west of England. Herbicide and fungicide exposures were weakly associated with a diagnosis of lymphoma in the univariable analysis. After accounting for the age at diagnosis and breed in the multivariable analysis, herbicide exposure was associated with a diagnosis of lymphoma. Clinical Significance The heterogeneous distribution of lymphoma in UK dogs provides further evidence for geographic variation of lymphoma, perhaps in part associated with underlying environmental risk factors. The results suggest an association between environmental herbicide and canine lymphoma.

Background Radiation therapy is commonly used as an adjunct to incomplete surgical excision in dogs with mast cell tumors (MCT), but the optimal dose and fractionation regimen have yet to be determined. Hypothesis We assessed outcomes (time to local recurrence, patient survival and toxicity) of a large population of dogs with MCT that received adjunctive radiation therapy. Animals Three hundred dogs with 302 MCT treated using adjunctive radiation therapy. Methods Retrospective observational study. Clinical records of 4 veterinary radiation centers were reviewed. Results Local recurrence rates were similar regardless of radiation protocol with 6.6% of patients developing recurrent cutaneous MCT at a median of 526 days. Local recurrence rate was similar between high and low‐risk MCT. Mast cell tumor related death was reported in 19% of all dogs, with 13% of dogs with low‐risk MCT dying of their disease compared to 29% of dogs with high‐risk MCT. No SC MCT (SCMCT) recurred after radiation therapy and only 7% of dogs with SCMCT were reported to have died of their disease. Mild late toxicity was common in both protocols and severe late toxicity occurred in 1.9% of dogs many years after treatment. Conclusions and Clinical Importance Our study supports the use of adjunctive radiation for the long‐term control of incompletely or narrowly excised cutaneous and SCMCT in dogs. More moderate dose and fractionation protocols may be appropriate in the adjunctive treatment of low‐risk MCT in dogs. Large multicenter prospective studies are required to establish the optimal dose and fractionation for MCT of different risk categories.