Prognostic value of intratumoral vessel density in cutaneous mast cell tumors of the dog.

The biological behaviour of canine cutaneous mast cell tumours (MCTs) is highly variable. The aim of this study was to investigate whether intratumoral microvessel density (IMVD), as an indicator of angiogenesis, was predictive of biological behaviour in MCTs of canine skin, and to relate this parameter to histological grade and other histomorphological features. IMVD was evaluated by immunohistochemical labelling of the endothelial marker factor VIII (Von Willebrand's factor)-related antigen in 32 primary cutaneous MCTs. Computer image analysis was used to measure IMVD, expressed as the number of microvessels per square millimetre. Cases were assigned to low and high vessel density groups, the median value (14.1) being used as the "cut-off". Kaplan-Meier-estimated survival curves of the groups revealed that IMVD was significantly associated with survival time (P=0.046). One-way analysis of variance, performed to compare the IMVD values of tumours of different histological grades, showed a significant difference between grades I and III (P=0.0002). There was a significant difference in IMVD between moderately invasive and highly invasive tumours (P=0.002) and between tumours with different numbers of mitoses (P=0.0046). In multivariate analysis, performed to test the combined influence on survival of each parameter, only the mitotic index and IMVD were independent prognostic variables (P=0.00019). The relation of angiogenesis to biological behaviour and histological parameters of malignancy of cutaneous MCTs was consistent with previous findings in human and animal tumours.