Canine mast cell tumours part I: Clinical and survival outcomes.

BACKGROUND: Dogs have a species-specific susceptibility for developing mast cell tumours (MCTs). Mutations in the KIT proto-oncogene (KIT) are known to contribute to the neoplastic biology of mast cells. In dogs, the most common KIT mutation is an internal tandem duplication (ITD) in exon 11 which has been considered a useful prognostic supplement to traditional histopathological tumour grading. OBJECTIVE: The aim of this retrospective study was to explore the importance of KIT exon 11 ITD mutation status and known clinical and pathological indices in predicting prognosis in a cohort of Australian dogs diagnosed with MCT. METHODS: Clinical parameters, survival data, and KIT mutation status were collected and assessed for 220 dogs with cutaneous or subcutaneous MCT (n = 189 and n = 31, respectively). RESULTS: In at least one of the multivariable models, tumour grade (cutaneous Kiupel low or high grade) or tumour subcutaneous location, multiple concurrent MCTs, metastasis at the time of surgery, and senior age were statistically significant in predicting the outcome (MCT-related death and/or second MCT diagnosis) at 6- or 12-month post-tumour excision. KIT exon 11 ITD mutation status was not a significant predictor in any of the final multivariable models and was strongly correlated with high histological grade (p < 0.001). CONCLUSION: In this sample of dogs, tumour histological grading remained the single most powerful prognostic indicator for MCT outcome. However, concurrent evaluation of multiple prognostically significant parameters provides information of potential value to inform therapeutic management for each patient.

Successful treatment of multifocal pedal Prototheca wickerhamii infection in a feline immunodeficiency virus-positive cat with multiple Bowenoid in situ carcinomas containing papillomaviral DNA sequences.

CASE SUMMARY: A 16-year-old, castrated male, feline immunodeficiency virus (FIV)-positive, domestic shorthair cat developed multiple skin lesions. Most of these were Bowenoid carcinoma in situ and contained DNA sequences consistent with Felis catus papillomavirus type 2. Two additional lesions that developed in the skin and subcutaneous tissues between the digital and carpal pads on the left forelimb and right hindlimb were shown by cytology, histology and culture to be caused by Prototheca wickerhamii. These lesions failed to improve in response to systemic therapy treatment with itraconazole, but excision by sharp en bloc resection with follow-up oral itraconazole therapy proved curative for one lesion, although the other lesion recurred, necessitating a second surgery. RELEVANCE AND NOVEL INFORMATION: This is only the second reported case of feline protothecosis from Australia and the first case that has been cultured and identified to the species level. Also of great interest was the presence of multiple papillomavirus-associated neoplastic lesions, which may have afforded a portal of entry for the algal pathogen and the cat's positive FIV status; the latter might have impacted on both viral and algal pathogenesis by effects on immunocompetence.