Phyllodes tumours of the breast are rare. They grow quickly, but most are benign (though some are cancerous) and rarely spread outside the breast.  

Phyllodes tumours develop in the breast’s connective tissue, outside the ducts and lobules of the breast. They make up fewer than 1% of breast cancers and are most commonly diagnosed in women aged in their 40s.^[10] 

Read more about phyllodes tumours of the breast.