Juvenile fibroadenoma arising in ectopic breast tissue presenting as an axillary mass

The differential diagnosis of an axillary mass during childhood is extensive and malignant processes such as lymphoma or metastatic disease must be excluded. We describe an unusual case of a fibroadenoma growing within ectopic breast tissue located in the axilla in a 10 year old girl. The mass grew rapidly and was removed during an excisional biopsy. Histological evaluation revealed a diagnosis of fibroadenoma. Fibroadenoma of ectopic breast tissue has not previously been reported in the pediatric age group, and must be considered as part of the differential diagnosis for pediatric axillary masses.