A fibroadenoma is a common type of benign or noncancerous lump that can develop in the breast. Larger fibroadenomas may feel like a hard or rubbery marble that moves around under the skin.

Fibroadenomas are solid, benign tumors that develop within the breast tissue itself, composed of both glandular (milk-producing) and stromal (connective) tissue. They are among the most common ...