What is the next step in diagnosis for a 34-year-old woman with a 3x4 cm retroareolar breast mass and nipple retraction after an ultrasound (US) has been performed?

Core Needle Biopsy is the Next Step for a 34-Year-Old Woman with a Retroareolar Breast Mass

For a 34-year-old woman with a 3x4 cm retroareolar breast mass with nipple retraction who has already had an ultrasound, the next appropriate step is core needle biopsy under ultrasound guidance.

Rationale for Core Needle Biopsy

The ACR Appropriateness Criteria for palpable breast masses provides clear guidance in this case 1:

1. The patient has concerning clinical features:

   • Large mass (3x4 cm)
   • Nipple retraction (highly suspicious for malignancy)
   • Retroareolar location

2. Imaging workup sequence:

   • Ultrasound has already been performed (first-line imaging for women <30 years)
   • For suspicious findings on ultrasound, tissue sampling is warranted

3. Core needle biopsy advantages over FNA:

   • Superior sensitivity and specificity for palpable masses 1
   • Allows correct histological grading
   • Enables tumor receptor status evaluation if malignant
   • Preferred over FNA except in rare circumstances (e.g., lesion abutting implant)

Why Not Other Options?

A. FNA (Fine Needle Aspiration)

• Less accurate than core biopsy for palpable masses 1
• Limited tissue sampling prevents definitive diagnosis and grading
• Cannot reliably distinguish invasive from in-situ disease
• Does not allow for receptor status testing if malignant

B. Mammogram

• While mammography is valuable, the patient has already had an ultrasound
• For retroareolar carcinomas, mammography has lower sensitivity in this area compared to other breast regions 2
• With a suspicious palpable mass and nipple retraction already identified, proceeding directly to tissue diagnosis is appropriate

C. MRI

• Not indicated as the next step for a palpable mass with suspicious features 1
• MRI may be useful later for staging if malignancy is confirmed, but not for initial diagnosis
• ACR guidelines clearly state: "There is no evidence to support MRI breast without and with contrast as the next step in evaluating a palpable mass with suspicious sonographic features" 1

Special Considerations for Retroareolar Masses

Retroareolar breast carcinomas have specific characteristics:

• Often present as palpable masses (78% in one study) 2
• May be associated with nipple inversion/retraction (as in this case)
• Ultrasound typically shows hypoechoic masses 2, 3
• Core biopsy under ultrasound guidance is particularly valuable for these lesions

Practical Approach

1. Perform ultrasound-guided core needle biopsy of the retroareolar mass
2. Place a post-biopsy marker clip
3. Obtain post-biopsy imaging to confirm accurate sampling
4. If malignancy is confirmed, additional imaging (including mammography and possibly MRI) may be needed for complete staging

Common Pitfalls to Avoid

• Delaying tissue diagnosis with additional imaging when suspicious features are present
• Using FNA instead of core biopsy for initial evaluation of suspicious breast masses
• Performing biopsy without image guidance, which reduces diagnostic accuracy
• Failing to place a marker clip, which is essential for surgical planning if malignancy is found

Core needle biopsy under ultrasound guidance is the most appropriate next step to establish a definitive diagnosis for this concerning retroareolar breast mass.