Increased microvessel density in malignant and borderline mammary phyllodes tumours

Aims: Tumour vascularity is considered a prognostic indicator in breast carcinoma, but its utility in mammary phyllodes tumour was not been explored. The authors report the correlation between intratumoral microvessel density and the histological grade of phyllodes tumour. Methods and results: Forty cases of phyllodes tumour were reviewed for stromal cellularity, overgrowth, cytological pleomorphism, mitotic count and margin pattern, Using established criteria, these were diagnosed as benign (n = 28), borderline (n = 10) and malignant (n = 2). Microvessel density was counted on CD31-stained slides as the number of vessels per high power field. For benign phyllodes tumour, the range was 7-26.2 (mean 13.1); for borderline phyllodes tumour the range was 17.2-32.5 (mean 22.4); for malignant phyllodes tumour the range was 25.9-33.3 (mean 29.6). The difference between the benign and borderline groups was significant (P < 0.0001) but that between the borderline and malignant groups was not, due to the small number of malignant cases. Conclusions: There is a significant difference in stromal microvessel density between benign and borderline phyllodes tumour. Although the small number of cases of malignant phyllodes tumour limits further interpretation, we believe that microvessel density can be used as an additional objective histological parameter in the evaluation of phyllodes tumour.