What is the next step for a 5 mm septated breast cyst?

Management of a 5 mm Septated Breast Cyst

A 5 mm septated breast cyst should be classified as a complex cyst and requires tissue biopsy (core needle biopsy) due to its higher risk of malignancy (14-23%) 1.

Classification of Breast Cysts

Breast cysts are classified into three categories based on ultrasound evaluation:

1. Simple cysts:

   • Anechoic (cystic), well-circumscribed, round or oval
   • Well-defined imperceptible wall and posterior enhancement
   • Benign (BI-RADS 2)
   • Routine screening recommended

2. Complicated cysts:

   • Has most but not all elements of a simple cyst
   • May contain low-level echoes or intracystic debris
   • No solid elements, intracystic masses, thick walls, or thick septa
   • Low risk of malignancy (<2%) (BI-RADS 3)

3. Complex cysts:

   • Has discrete solid components
   • May include thick walls, thick septa, and/or intracystic mass
   • Higher risk of malignancy (14-23%)
   • BI-RADS 4-5

Management Algorithm for a 5 mm Septated Breast Cyst

A septated breast cyst contains internal septa, which classifies it as a complex cyst according to the NCCN guidelines 1. The presence of septa is a key feature that distinguishes it from simple or complicated cysts.

Step 1: Classification

• The presence of septa in a breast cyst classifies it as a complex cyst
• Complex cysts have a relatively high risk of malignancy (14-23%) 1, 2

Step 2: Recommended Management

• Tissue (core needle) biopsy is the recommended next step 1
• This is preferred over aspiration or observation due to the higher malignancy risk

Step 3: Post-Biopsy Management

If the biopsy result is:

• Benign and image-concordant: Physical examination with or without ultrasound or mammogram every 6-12 months for 1-2 years 1
• Benign but image-discordant or indeterminate: Surgical excision 1
• Atypical hyperplasia, LCIS, or other concerning pathology: Surgical excision (though select patients may be suitable for monitoring) 1
• Malignant: Treatment according to breast cancer guidelines

Evidence Strength and Considerations

The NCCN guidelines provide clear recommendations for the management of complex cysts, including those with septations 1. These guidelines are considered the gold standard for breast cancer screening and diagnosis.

Research studies support this approach:

• Complex cystic lesions with septations have been found to have malignancy rates of 23-31% in case series 2
• A study of 175 cystic breast lesions found that cysts with thick septa had a significantly higher risk of malignancy 3

Important Caveats

1. Size consideration: While the 5 mm size is small, the presence of septations is more important than size in determining management 1

2. Avoid aspiration as primary management: Unlike simple or complicated cysts, complex cysts should not be managed with aspiration alone due to the higher risk of malignancy 1, 3

3. Correlation with clinical findings: Ensure concordance between imaging and clinical findings. If there is discordance, further evaluation is necessary 1

4. Biopsy technique: Core needle biopsy is preferred over fine needle aspiration (FNA) for complex cysts, as FNA may not adequately sample the solid components and requires cytologic expertise 1

5. Follow-up importance: If biopsy confirms benign pathology, follow-up is still essential to ensure stability of the lesion 1