Fibroadenoma is a lump composed of glandular or fibrous tissue with clearly defined edge in the breast. Fibroadenoma is also termed as breast mice or breast mouse for the fact that it is highly mobile in the breast and would often run away if an attempt is made to touch it. Though it is non-cancerous, a doctor may still recommend biopsy on spotting it.

There can be multiple fibroadenomas in the breasts. These are typically an inch in diameter and the ones bigger than that are called giant fibroadenomas. While the cause of these painless lumps is not known as of now, changes in reproductive hormones are thought to be the major reason behind them.

In most of the cases, fibroadenomas are left as such, though periodic monitoring is done. In some of the cases, surgical intervention is required to remove the lump. However, the tissue might be examined to check if there is any cancerous growth.