Breast, juvenile fibroadenoma

Juvenile fibroadenoma of the breast is a tumour of adolescence characterized by rapid growth, and large size. Histologically it exhibits a biphasic (epithelial and stromal) pattern. It is characterized by hypercellular stroma and intraductal epithelial hyperplasia. It also commonly exhibits features in common with gynecomastoid hyperplasia, often distinguishing the juvenile-type from a conventional fibroadenoma, which has a canalicular-type architecture. Although the stroma can be cellular with scattered mitoses, the leaf-like architecture and peri-epithelial stromal condensation seen in phyllodes tumours are not present.