The lesion shown is circumscribed, by the skin on one surface and by fat and a little muscle on the
undersurface. There is recognisable, apparently normal, breast tissue at one pole. The lesion is
formed by an irregularly nodular mass in which there are large cystic spaces. There are also areas
of haemorrhage apparent.
This lesion had been present for some years in a women who was 23 years old when the
breast was removed. Histologically the solid areas are formed by spindle-shaped cells showing
little variation in size and almost no mitotic activity. The lesion has been variously described as
cystosarcoma phyllodes (foliage-like, branching protruberances of tumour tissue within cystic
spaces) and as giant fibroadenoma. A small proportion of these tumours metastasize so that the
name fibrosarcoma is probably appropriate. The patient is alive and well and free of metastatic
disease 20 years after the breast was removed.