Multivariate survival analysis of histological parameters and clinical presentation in canine cutaneous mast cell tumours.

The Patnaik histological grade is a good method for the prediction of long-term mast cell tumour behaviour but it is influenced by subjective inter-observer variations and intratumoral heterogeneity. The present study evaluated each of the histopathological parameters used to formulate Patnaik's grade in terms of prognosis and tested whether they have a different prognostic sensitivity, thereby disclosing which could be considered more useful in the prediction of tumour recurrence and patient survival. Clinical presentation (single or multiple tumours) was also considered as possible prognostic factor. The results demonstrated that individual histological criteria together with multiple presentation may be of value in predicting the outcome of mast cell tumours. Among these, invasiveness (beta1.85; standard error 1.15) and the number of mitotic figures (beta3.01; standard error 1.18) showed high prognostic significance (Cox proportional hazard regression for censored data; chi-squared = 15.52, degree of freedom = 6, p = 0.016) and could serve as reliable prognostic indicators avoiding more subjective parameters such as cellular differentiation, nuclear morphology and tumoural pattern.