What are the causes and treatments of breast cysts formation?

Breast Cyst Formation: Causes and Management

Etiology

Breast cysts arise as an aberration of normal lobular involution under hormonal stimulation, with active secretion from apocrine epithelium being the primary mechanism. 1

• Cysts are the most common breast disorder, occurring in approximately 7% of adult women 1
• Peak occurrence is between ages 40-50 years, with 76% occurring in premenopausal women 2
• Only 5% occur in women over age 60, and postmenopausal cysts rarely recur 2
• Cyst recurrence patterns: 60% have no recurrence, 36% have 2-5 recurrences, and 4% have more than 5 recurrences 2

Classification and Risk Stratification

The NCCN classifies breast cysts into three categories based on ultrasound characteristics, each requiring distinctly different management approaches. 3, 4, 5

Simple Cysts (BI-RADS 2)

• Ultrasound features: Anechoic, well-circumscribed, round or oval with imperceptible wall and posterior acoustic enhancement 3, 6
• Malignancy risk: Essentially zero—not associated with subsequent breast cancer development 3, 5
• Management: Routine screening only if clinical and imaging findings are concordant 3, 5

Complicated Cysts (BI-RADS 3)

• Ultrasound features: Low-level internal echoes or debris without solid components, thick walls, or thick septa 3, 6
• Malignancy risk: Very low (<2%) 3, 4, 7
• Management options: Either aspiration or short-term surveillance 3, 4

Complex Cysts

• Ultrasound features: Discrete solid components including thick walls, thick septa, and/or intracystic masses 3, 6
• Malignancy risk: 14-23% 3, 5, 8
• Specific high-risk features: Thick cyst wall, lobulation, and hyperechogenicity are predictive of malignancy, with two or more criteria conferring a 13.6-fold higher risk 8
• Management: Immediate core needle biopsy required 3, 5

Treatment Algorithm

For Simple Cysts

• No intervention required if asymptomatic and concordant with clinical findings 3, 5
• Elective aspiration only for symptomatic patients, with typical cyst fluid discarded 9
• Return to routine screening 3

For Complicated Cysts

Follow a surveillance-based approach unless specific indications for aspiration exist. 4, 5

• Primary approach: Physical examination and ultrasound ± mammography every 6-12 months for 1-2 years 3, 4
• Follow-up interval varies based on level of suspicion 3, 4
• Aspiration indications: Symptomatic patients or those likely to be lost to follow-up 4
• If bloody fluid obtained: Place tissue marker, perform cytologic evaluation, proceed to vacuum-assisted biopsy or surgical excision if cytology positive 5
• If stable or decreasing: Continue follow-up until 1-2 years of stability documented, then return to routine screening 4
• If increasing in size or developing suspicious features: Perform core needle biopsy 3, 4

For Complex Cysts

Immediate tissue biopsy with core needle technique is mandatory due to the 14-23% malignancy rate. 3, 5, 8

• Core needle biopsy preferred over fine needle aspiration for definitive diagnosis 4
• After benign concordant biopsy results: Follow-up with physical examination at 6-12 months ± imaging for 1 year to ensure stability 4, 5
• Surgical excision required for increasing lesions 5

Critical Pitfalls to Avoid

• Never dismiss complex cysts with surveillance alone—the 14% malignancy rate demands immediate biopsy 8
• Do not confuse complicated cysts (low-level echoes, <2% malignancy risk) with complex cysts (solid components, 14-23% malignancy risk) 3, 7, 8
• Cytologic examination of aspirated fluid is required only if bloody 4, 9
• Ensure concordance between pathology, imaging, and clinical findings when needle biopsy is performed 3
• Geographic correlation between clinical and imaging findings must be confirmed; if lacking, further evaluation is necessary 3