Multifocal histogenesis of a cystosarcoma phyllodes.

An unusual multifocal cystosarcoma phyllodes is reported. It presented as a small, circumscribed tumour mass, which was associated with two diffuse neoplastic lesions which arose sequentially in two geographically separate parts of the mammary disc. Microscopically the tumour appeared to have been enlarging by the formation of isolated satellite tumour nodules within the adjacent normal breast tissue, which represents a third, though rarer way in which a cystosarcoma phyllodes may enlarge.