While gynecomastia is common in adolescents, male breast cancer in the pediatric population is exceedingly rare. Occasional reports describe malignant and pre-malignant lesions in mastectomy specimens for gynecomastia in young adults. We present a 16-year-old male with unilateral gynecomastia discovered to have ductal carcinoma in situ (DCIS), treated by mastectomy with 4 year follow-up.