The stroma of fibroadenoma and phyllodes tumor consists of fibroblas-tic proliferation. Rarely the stroma contains bundles of smooth muscle. Vascular stroma is not a feature of fi­broadenoma. We report a case of a 34-year old Chinese woman present­ed with a huge mass occupying much of the entire left breast. Left mastecto­my was performed and showed a large well-circumscribed lobulated rubbery firm tumor measure 13x10x6cm. Microscopic examination revealed a remarKable neoplasm in a form of fibroepithelial tumor formed by an organoid pattern of ductal struc­tures with very striking stromal ap­pearance composed of extensive vas­cular proliferation throughout the tumor confirmed by strong immunoreaction for the endothelial cell mark­ers CD31, CD34 and factor VIII. Ultra-structural examination confirm the en­dothelial nature of the lining of the vascular channels in the stroma which showed spindle cells with intercellular junctions, Basal lamina, Pinocytotic vesicles and some weibel-Palade bodies. Those finding rule out the di­agnosis of pseudoangiomatous hy-perpiasia. The patient developed a lo­cal recurrence few months latter and the resection showed a malignant phyllodes tumor with ductal carcino­ma in situ.In conclusion we described the fi­rst reported case of a unique giant fi­broadenoma with abnormal vascular proliferation with recurrence as malig­nant phyllodes tumor associated