What is the best imaging modality for a postmenopausal woman with a new breast bruise on anticoagulation therapy after a recent knee replacement?

Breast Ultrasound is the Most Appropriate Imaging Modality for a Postmenopausal Woman with a Breast Bruise on Anticoagulation

Breast ultrasound is the most appropriate initial imaging modality for evaluating a quarter-sized, purple-blue bruise on the right lateral breast in a postmenopausal woman on anticoagulation therapy following knee replacement surgery. 1

Clinical Scenario Assessment

The patient presents with:

• Quarter-sized bruise on right lateral breast
• Purple-blue coloration
• Non-tender to touch
• No swelling or nipple discharge
• No reported injury
• Recent right knee replacement (7/7/25)
• Currently on ASA BID (anticoagulation therapy)
• Using walker for ambulation
• Attending physical therapy twice weekly
• Mammogram is up to date

Imaging Recommendation Algorithm

First-Line Imaging: Breast Ultrasound

Ultrasound is the imaging modality of choice for this clinical scenario because:

1. Excellent for distinguishing fluid from solid tissue: Ultrasound can effectively differentiate between a simple hematoma (expected with anticoagulation) versus a solid mass 1, 2

2. No radiation exposure: Important consideration in a patient who may need multiple follow-up examinations 1

3. High sensitivity for palpable abnormalities: According to ACR Appropriateness Criteria for palpable breast masses, ultrasound has high sensitivity (84%) for detecting abnormalities 1

4. Appropriate for anticoagulated patients: No need to discontinue anticoagulation therapy for the examination 1

5. Can guide intervention if needed: If aspiration or biopsy is required, ultrasound provides real-time guidance 1

Second-Line Imaging (If Ultrasound Is Inconclusive):

• Diagnostic mammography/tomosynthesis: Consider if ultrasound findings are equivocal, but this would be a secondary approach since the patient's mammogram is already up to date 1

• MRI breast without and with IV contrast: Only if ultrasound and mammography are inconclusive and there is high clinical suspicion for malignancy 1

Clinical Considerations in This Case

Anticoagulation Impact

• Patients on anticoagulation therapy (ASA BID in this case) have increased risk of spontaneous bruising and hematoma formation 3, 4
• The recent knee replacement (7/7/25) and use of a walker suggest potential for minor trauma that may have gone unnoticed

Key Differential Diagnoses

1. Simple hematoma: Most likely given anticoagulation therapy
2. Fat necrosis: Can develop following trauma, even minor unnoticed trauma
3. Underlying mass with hemorrhage: Less likely but important to exclude

Potential Pitfalls to Avoid

• Delaying imaging: Despite anticoagulation being a likely explanation, imaging should not be delayed to rule out underlying pathology
• Relying solely on mammography: While mammography is excellent for screening, ultrasound is superior for characterizing palpable abnormalities and fluid collections 1, 5
• Overlooking the need for follow-up: If a hematoma is diagnosed, follow-up imaging should be scheduled to ensure resolution

Follow-up Recommendations

• If ultrasound confirms simple hematoma: Follow-up imaging in 4-6 weeks to ensure resolution
• If ultrasound shows complex or suspicious features: Consider image-guided biopsy
• If ultrasound is normal but clinical concern persists: Consider diagnostic mammography with tomosynthesis as the next step 1

Breast ultrasound represents the optimal balance of diagnostic accuracy, patient safety, and resource utilization for evaluating a breast bruise in a patient on anticoagulation therapy following orthopedic surgery.