Pain in the right armpit developed in a 26-year-old woman 2 days after a normal vaginal delivery. Physical examination revealed a round, firm, well-circumscribed axillary mass (Panel A) that released a white discharge when pressed (Panel B). This finding was consistent with polymastia, a condition in which accessory breast tissue develops along the former embryonic mammary ridge. In the postpartum period, milk can drain from the tissue, which may become enlarged, in some instances causing pain and discomfort. The differential diagnosis included lymphadenopathy and lipoma. The patient was reassured that the condition is benign. In patients with polymastia, it is important that routine screening for breast cancer include examination of the accessory tissue.