Cystic lesions of the breast may present in women of any age but are most common between 30 and 50 years of age (Table 1). They may be detected. A breast cyst is a fluid-filled sac within the breast. One breast can have one or more breast cysts Ultrasound can also show if the cyst contains solid nodules, a sign that the lesion may be pre-cancerous or cancerous. Examination by a.