RADIOLOGY: BREAST: Case# 32944: CYST. 35 year old for screening mammogram. Close up view of mammogram shows a small, well circumscribed lesion. Cysts are thought to form from lobules that become progressively distended by fluid secretion, or from obstructed ducts. Usually they are multiple, but they may be single. Mammographically, they appear as rounded or slightly lobulated lesions with well circumscrebed margins. The diagnosis may be confirmed if the lesion disapears following needle aspiration.