Breast fibroadenomas There are many types of breast lumps, fibroadenas are one of them. Breast fibroadenomas are the most common type of benign breast lump. They're made up of fibrous connective tissues that support the mammary gland and lobes that have developed hyperplasia---an enlargement due to an increased rate of cellular reproduction. Many women experience them as marbles and firm and able to be move easily around by pressing or pushing on the skin. Fibroadenomas can be experienced during your breast self-exam and will show up on mammograms and ultrasounds. Women who are under 30s are most likely to develop a breast fibroadenoma, which may grow larger during pregnancy or breastfeeding. Symptoms Symptom of a fibroadenoma is a small lump in the breast which you may experienced during a self-exam. These lumps feel firm, round or ovale, smooth, rubbery texture , and are movable. Fibroadenomas are so mobile that sometimes these refer as “breast mice,” as ...