Grade II mast cell tumours (MCT) are tumours with variable biologic behaviour. Multiple factors have been associated with outcome, including proliferation markers. The purpose of this study was to determine if extent of surgical excision affects recurrence rate in dogs with grade II MCT with low proliferation activity, determined by Ki67 and argyrophilic nucleolar organising regions (AgNOR). Eighty-six dogs with cutaneous MCT were evaluated. All dogs had surgical excision of their MCT with a low Ki67 index and combined AgNORxKi67 (Ag67) values. Twenty-three (27%) dogs developed local or distant recurrence during the median follow-up time. Of these dogs, six (7%) had local recurrence, one had complete and five had incomplete histologic margins. This difference in recurrence rates between dogs with complete and incomplete histologic margins was not significant. On the basis of this study, ancillary therapy may not be necessary for patients with incompletely excised grade II MCT with low proliferation activity.

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Canine cutaneous mast cell tumors (ccMCTs) have a highly variable biological behavior and accurate prognostication is essential for therapeutic intervention. Internal tandem duplications (ITD) of exon 11 are the most commonly detected c-kit mutation in ccMCTs and are associated with poor prognosis and increased cellular proliferation. The prognostic value of detecting mutations in other exons of c-kit has not been systematically examined. In this study, we analyzed the prognostic value of ITD mutations of exon 8 in c-kit of ccMCTs in comparison to ccMCTs with ITD mutations of exon 11 and ccMCTs without mutations of exon 8 or 11. The mutational status, histological grade, KIT expression pattern, Ki67 index, AgNOR (argyrophilic nucleolar organizing region) score, and Ag67 score were determined in 221 ccMCTs, and outcome was available for 101 dogs. ITD mutations of exon 8 were found in 73/221 (33%), of exon 11 in 100/221 (45%), and none of these mutations in 50/221 (22%) of ccMCTs. None of the dogs with mutations of exon 8 died due to suspected ccMCT-related cause, but 23% dogs with ccMCTs with mutations of exon 11 died due to suspected ccMCT-related cause. Prognostic parameters in ccMCTs with exon 11 mutations were commonly associated with a high proliferative activity and poor prognosis, while prognostic markers in ccMCTs with mutations of exon 8 had lower values similar to those observed in ccMCTs without mutations in exons 8 or 11 of c-kit. This study indicates that screening for ITD mutations in exon 8 in ccMCTs may be helpful to identify less aggressive ccMCTs and may be recommended as a supplementary prognostic test.

Two littermates, a young male and female boxer, were admitted to the Utrecht University’s Department of Clinical Sciences of Companion Animals within a three month period. Both dogs suffered from anaemia caused by chronic intestinal blood loss, vomiting and weight loss. In both cases, there was no response to conservative medical management. Eventually, the dogs suffered significant gastrointestinal haemorrhage that resulted in collapse. Gastroduodenoscopy and exploratory surgery showed a duodenal diverticulum in both dogs. This is the first report that describes this congenital anomaly in two siblings.

Objective-To evaluate efficacy of hypotonic water as adjuvant therapy after marginal resection of canine mast cell tumors (MCT). Study Design-Double-blinded, placebo-controlled, prospective, randomized study. Animals-Dogs (n ¼ 30) with spontaneous, cutaneous, solitary MCT. Methods-The wound bed of MCT, resected with margins o0.5 cm, was injected with either hypotonic or isotonic water according to a standardized protocol. Follow-up was obtained by clinical examination at 1, 2, 3, 6, and 12 months and annual telephone contact with the owner. Results-Eighteen dogs were treated with isotonic lactated Ringer's solution and 12 dogs with hypotonic distilled water. All MCT were stage 0 tumors and most grade II. Six tumors (4 isotonic, 2 hypotonic) recurred locally, 3 of these dogs died from disease-related reasons within 4 months. The surviving 3 dogs were alive with a median survival time (ST) of 1092 days. The calculated 2-year recurrence-free rate was 92.7%; the 2-year disease-free rate 79.1%; and the 2-year survival rate 89.5%. No significant differences in local recurrence and ST were observed between treatment groups. Histologic grading was the only significant prognosticator for ST and recurrence-free periods. Conclusion-No significant differences in local recurrence and ST were observed between adjunctive hypotonic water and placebo treatment after marginal resection of solitary MCT. Clinical Relevance-Hypotonic water does not decrease the rate of local recurrence in dogs with solitary MCT after marginal surgical excision. r