16 Dec 2025
Some indicators found to be more useful than previously thought, while one proved less effective than expected.
Chris Simpson
Job Title
A study has offered fresh insight into how veterinary professionals can more accurately predict outcomes for dogs with mast cell tumours (MCTs).
Scholars examined data from a large UK-based commercial diagnostic laboratory – CVS’ Finn Pathologists – and the RVC VetCompass database.
The retrospective cohort study analysed 199 tumours from 197 dogs under primary practice care that had undergone additional prognostic testing, with the goal of providing greater clarity than the traditional Patnaik and Kiupel grading systems.
The authors noted that between 16 and 20% of all cutaneous and subcutaneous tumours in dogs are MCTs, and more than half of cutaneous MCTs fall into Patnaik grade II and Kiupel “low” grade categories, which are known to result in a wide range of clinical outcomes.
A broad panel of prognostic markers were examined; mitotic count (a measure of how quickly cells are dividing), Ki67 (a proliferation marker), AgNOR (a marker of nucleolar activity), KiAg (a combination of Ki67 and AgNOR), KIT staining pattern and genetic mutations in the c-kit gene (specifically exons 8 and 11).
The authors aimed to identify which markers could independently predict mast cell tumour-specific survival and the likelihood of tumour recurrence.
While the study did not identify a single factor with consistently high predictive prognostic value, it did find that a c-kit mutation in exon 11 was the only marker that independently predicted survival in Patnaik grade I/II and Kiupel low-grade cutaneous tumours.
The c-kit mutation in exon 11 and AgNOR counts above 2.25 per cell were also independently significant in predicting tumour recurrence.
In line with previous studies, a higher mitotic count also proved a strong independent histological predictor of poor survival across all tumour types, but unexpectedly Ki67 was not independently significant.
Both cutaneous and subcutaneous MCTs behaved similarly in terms of survival and recurrence.
No significant difference in recurrence was found between incomplete excision and a histological tumour-free margin of less than 2mm, although the authors advised interpreting this with caution.
Lead author Owen Davies, a veterinary oncology specialist at Bristol Vet Specialists, said: “This study shows that no single test can predict outcomes for every dog with a mast cell tumour.
“But we found that c-kit mutation in exon 11 and AgNOR may be more useful than previously thought, and Ki67 may be less useful than previously thought.
“We hope this helps vets make more informed decisions and tailor treatment plans more effectively.”
