Phyllodes tumours of the breast account for fewer than one percent of all breast cancers, and only 20 to 25 percent of these are malignant. They rarely spread to other organs, but do tend to grow quickly.
At times difficult to diagnose, phyllodes tumours must be differentiated from benign fibroadenomas, which typically appear between the ages of 30 and 40, as opposed to phyllodes which usually appear in between 40 and 50 years of age. These tumours, whether benign or malignant, require treatment due to their fast growth, which can create a visible lump on the breast and sometimes even break through the skin, causing pain and discomfort.
The main difference between the benign and malignant tumours is that malignant tumours may recur more quickly, and are able to spread beyond the breast.