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Breast cysts are circumscribed fluid collections that most commonly occur in premenopausal women. The typical presentation includes single or multiple breast masses of variable size that may be tender. Because cysts cannot be reliably distinguished from a solid mass on palpation or mammography, the diagnostic evaluation requires a breast ultrasound. Based on ultrasound findings, breast cysts are characterized as simple, complicated, or complex. Complex breast cysts are associated with an increased risk of malignancy and should be biopsied. Complicated breast cysts are typically benign; a biopsy should be considered if there is clinical suspicion of malignancy. Simple breast cysts are benign and seldom require any further diagnostics. Management depends on the type of cyst and risk of malignancy and includes surveillance, therapeutic aspiration, and surgical excision.
- Follow .
- Use targeted ultrasound to evaluate any masses identified on mammography. 
- Tailor further management based on imaging findings.
Cytological evaluation is recommended if bloody fluid is obtained on therapeutic or diagnostic aspiration. 
Characterization of breast cysts 
|Types of breast cysts |
|Simple breast cyst||Complicated breast cyst||Complex breast cyst|
|Characteristic features on ultrasound|| |
|Risk of malignancy|| || || |
Management of simple breast cysts 
- Asymptomatic cysts: : no intervention required; most resolve spontaneously 
- Symptomatic cysts : Consider ultrasound-guided fine needle aspiration. 
Management of complicated breast cysts 
Management depends on patient preferences and clinical concern for malignancy and includes the following.
- Surveillance: close clinical and imaging follow-up over 1–2 years 
- Therapeutic fine needle aspiration: Any bloody aspirate should be sent for cytology.
- Core needle biopsy is indicated if there is clinical suspicion for malignancy, such as: