What is the best course of action for a female of childbearing age with a history of breastfeeding, granulomatous mastitis (inflammatory breast condition), and duct ectasia (abnormal dilation of milk ducts), presenting with a large right breast lump, nipple inversion, and previous blood discharge from the right breast?

Urgent Breast Clinic Referral is Mandatory for This Patient

This patient requires immediate breast clinic referral and comprehensive imaging evaluation given the concerning constellation of findings: a large 9-10cm breast mass with nipple inversion, history of bloody nipple discharge, and prior granulomatous mastitis—malignancy must be excluded urgently. 1, 2

Critical Red Flags Requiring Urgent Evaluation

This presentation contains multiple high-risk features that mandate urgent specialist assessment:

• Large palpable mass (9-10cm) with significant growth - This size and progression pattern raises substantial concern for malignancy, particularly given the history of granulomatous mastitis which can mask or mimic breast cancer 3, 4
• Nipple inversion with scarring - New or progressive nipple retraction is a classic sign of underlying malignancy, though it can occur with benign inflammatory conditions 5, 6
• Previous bloody nipple discharge - Up to 12% of patients with ductal carcinoma in situ (DCIS) present with nipple discharge, and pathologic discharge carries a 5-21% risk of underlying malignancy 7, 8
• History of granulomatous mastitis - This condition frequently mimics inflammatory breast carcinoma both clinically and mammographically, making definitive diagnosis challenging 3, 4

Recommended Imaging Algorithm

Initial imaging should include diagnostic mammography (or digital breast tomosynthesis) with complementary ultrasound of both breasts, as this patient is of childbearing age and presents with pathologic findings. 1, 2

First-Line Imaging:

• Diagnostic mammography/DBT - Rated 9/9 appropriateness by the American College of Radiology for women ≥30 years with pathologic breast findings 1
• Bilateral breast ultrasound - More sensitive than mammography for identifying intraductal lesions, though with lower specificity; essential for evaluating the retroareolar region 7

Advanced Imaging if Initial Studies Are Negative or Equivocal:

• Breast MRI - Has sensitivity of 86-100% for invasive cancer and 40-100% for noninvasive disease in patients with pathologic nipple discharge; higher positive and negative predictive values than ductography 7, 8
• Ductography - May be considered but has 10-15% technical failure rate and is invasive; MRI is increasingly preferred 7, 1

Tissue Diagnosis is Essential

Image-guided core needle biopsy (CNB) is mandatory for any identified lesions, as imaging alone is unreliable for predicting histology in patients with pathologic breast findings. 7

• CNB is superior to fine-needle aspiration for sensitivity, specificity, and correct histologic grading 1
• Vacuum-assisted CNB is particularly useful for complete sampling of small intraductal papillary lesions 7
• A negative mammogram and ultrasound reduce malignancy risk to approximately 0%, but given this patient's concerning clinical findings, tissue diagnosis remains critical 1

Differential Diagnosis Considerations

Recurrent Granulomatous Mastitis:

• Affects women of childbearing age with history of breastfeeding (this patient is currently breastfeeding from contralateral breast) 4, 5
• Recurrence rate of 23% after treatment 3
• Presents with painful breast mass, erythema, and can cause nipple retraction 5, 6
• However, the 9-10cm size and significant growth pattern are atypical and concerning 3, 9

Malignancy:

• Must be excluded given the size, growth, nipple changes, and history of bloody discharge 1, 8
• Granulomatous mastitis can mask or mimic inflammatory breast carcinoma 3, 4
• The patient's previous refusal of breast clinic referral after ultrasound showing only inflammatory changes represents a critical missed opportunity for earlier evaluation 3

Critical Pitfalls to Avoid

• Do not attribute findings solely to recurrent granulomatous mastitis without tissue diagnosis - The clinical presentation overlaps significantly with malignancy 3, 4
• Do not delay imaging due to breastfeeding status - Breast imaging during lactation is very similar to imaging in non-breastfeeding women and should not be postponed 7
• Do not rely on negative previous ultrasound - That study was performed at an earlier time point and showed only mild duct ectasia; the current 9-10cm mass represents significant interval change 1
• False-positive ultrasound results can occur due to volume averaging with ductal wall in tortuous ducts, intraductal and periductal fibrosis, or adherent blood clots 7, 1

Management During Breastfeeding

• The patient can continue breastfeeding from the unaffected left breast during evaluation 6
• Diagnostic imaging (mammography and ultrasound) is safe during lactation 7
• If tissue diagnosis confirms recurrent granulomatous mastitis and treatment with intralesional steroids is planned, breastfeeding from the affected breast must be discontinued 6

The urgent breast clinic referral decision is absolutely correct and should be expedited given the high-risk clinical presentation. 1, 2