Fibroadenomas are the most common benign tumors of the female breast. These tumors often grow as a spherical nodule ranging in size from under 1 cm to 10-15 cm (giant fibroadenomas). They are most frequently 2-4 cm in diameter. Their cut surface is white to gray and have a rubbery consistency.

Microscopically, fibroadenomas consist of a delicate fibroconnenctive tissue stroma. Within the stroma, either glandular sturctures, uncompressed by the stroma, have a round to oval lumen (pericanalicular fibroadenoma) or have a slit like appearance (intracanalicular fibroadenoma). The glandular lining consists of a single or multiple layers of epithelial cells. In some instances, the entire tumor consists of glands (tubular adenoma) with lillte intervening stroma. This form is often encountered during pregnancy (lactating adenomas).