Open Label Arimidex in Gynecomastia

Inclusion Criteria: Signed informed consent/assent (as per local requirements), males aged 11-18 yrs. (after his 10th and prior to 19th birthday), gynecomastia, one breast measuring ≥ 2 cm in diameter (by ultrasound or caliper measurement) that has not decreased during the prior 3 month period by medical history and has been present for 12 months or less (date of onset based on best estimate of treating physician after discussion with patient and or patient's parent/guardian), normal renal liver and thyroid function, no evidence of hormone producing tumor, no evidence of hypogonadism or androgen resistance. Exclusion Criteria: Patients who have been given medications known to cause gynecomastia within the previous 6 months, involvement in the planning and conduct of the study (includes AZ staff and investigative site staff), previous enrollment in the present study, investigators opinion patient would be unable to comply with study protocol.