Bilateral accessory axillary breast tissue in a premenarchal female.

A 9-year-old premenarchal female presented to pediatric dermatology with a 6-month history of periodically tender, bilateral and symmetric axillary masses. Magnetic resonance imaging and subsequent surgical excision confirmed the diagnosis of bilateral accessory axillary breast tissue. Accessory axillary breast tissue is a rare condition seen most in pubertal, pregnant and breastfeeding women. However, it can arise in pre-adolescent patients and should be added to the differential diagnosis of an axillary mass.