What are the possible causes and treatments for a rash on the breast?

Evaluation and Management of Breast Rash

Any unusual skin changes on the breast require immediate diagnostic evaluation with bilateral diagnostic mammogram ± ultrasound, followed by skin biopsy if imaging is benign, because these changes may represent life-threatening malignancies including inflammatory breast cancer or Paget's disease. 1

Critical Diagnoses to Exclude First

Inflammatory Breast Cancer (IBC)

• IBC must be ruled out urgently when erythema and dermal edema (peau d'orange appearance) involve one-third or more of the breast skin with a palpable border to the erythema 1, 2
• This aggressive malignancy accounts for 1-6% of breast cancers and requires rapid diagnosis as delayed recognition significantly impacts survival 1, 3
• IBC is a clinical diagnosis and does not require positive biopsy confirmation to initiate workup 1
• Key features include rapid onset (within 6 months), warmth of affected breast, and lack of response to antibiotics 3

Paget's Disease of the Breast

• Suspect when nipple excoriation, scaling, eczema-like changes, bleeding, ulceration, or itching are present 1, 4
• This rare breast cancer presents with neoplastic cells in the nipple-areolar epidermis and is frequently confused with benign dermatologic conditions, causing diagnostic delays 1
• 80-90% of cases have associated underlying breast cancer (DCIS or invasive) elsewhere in the breast, not necessarily adjacent to the nipple 1, 4
• Pure Paget's disease is often occult on mammography, so negative imaging does not exclude the diagnosis 1, 4

Diagnostic Algorithm

Step 1: Initial Imaging

• Begin with bilateral diagnostic mammogram with or without ultrasound for any unusual breast skin changes, regardless of patient age 1, 4
• This is mandatory even if clinical suspicion is low 3

Step 2: Tissue Diagnosis Based on Imaging Results

If imaging shows BI-RADS category 1-3 (negative, benign, or probably benign):

• Perform punch biopsy of the skin or nipple biopsy 1, 4
• Antibiotics may be given if infection is suspected, but should not delay diagnostic evaluation 1
• If biopsy is benign but clinical suspicion remains, reassess clinical-pathologic correlation and consider breast MRI, repeat biopsy, and consultation with breast specialist 1

If imaging shows BI-RADS category 4-5 (suspicious or highly suggestive of malignancy):

• Perform core needle biopsy (preferred) with or without punch biopsy 1, 4
• Surgical excision is an alternative option 1
• If benign, still perform punch biopsy of skin if not already done 1

Step 3: Advanced Imaging for Confirmed Paget's Disease

• Breast MRI is strongly recommended when biopsy confirms Paget's disease to define extent of disease and identify additional lesions 1, 4

Common Pitfalls to Avoid

• Do not treat presumed infection or eczema empirically without tissue diagnosis if clinical features suggest IBC or Paget's disease 1
• A short trial (7-10 days) of antibiotics for suspected mastitis or topical steroids for suspected eczema may be considered only if clinical suspicion for malignancy is low, but this should not delay diagnostic workup 1, 4
• A benign skin biopsy does not rule out IBC if clinical suspicion is high; further evaluation is mandatory 1
• Never assume negative mammography excludes Paget's disease; skin biopsy is required 1, 4
• Do not confuse normal asymmetry or benign dermatologic conditions with malignant skin changes; when uncertain, always biopsy 4, 5

Benign Differential Diagnoses

While malignancy must be excluded first, benign causes include:

• Atopic, irritant, or allergic contact dermatitis affecting the nipple or breast skin 5, 6
• Bacterial mastitis (especially in lactating women) 7, 6
• Nipple candidiasis 5
• Radiation-induced skin changes in patients with prior breast cancer treatment 8, 6
• Psoriasis of the nipple 5

Treatment of benign conditions (only after malignancy excluded) includes topical corticosteroids or calcineurin inhibitors, avoidance of irritants, and intensive moisturization 5