Ultrasonography depicts the fluid within cysts and can diagnose cysts as small as 2 to 3 mm in diameter in small breasts, but not as easily in large, fatty breast tissue.
Simple cysts require only routine follow-up.
Cysts with debris or thick material inside need to be aspirated for definitive diagnosis. Aspiration of a cyst can be guided by palpation, ultrasound or mammography. Non-palpable simple cysts detected by mammography and confirmed by ultrasound do not need to be aspirated except to relieve pain. Non-bloody cystic fluid should not routinely be sent for cytological analysis, as the incidence of cancer is less than one percent. A cyst that recurs more than two times within four to six weeks, displays bloody fluid, or leaves a residual palpable mass post-aspiration demands cytologic examination and further evaluation.