What is the recommended diagnostic and management approach for an adult female patient presenting with breast dimpling, rash, and swelling, using Canadian guidelines, with a suspicion of underlying breast cancer?

Diagnostic and Management Approach for Suspected Inflammatory Breast Cancer or Paget's Disease

For an adult female presenting with breast dimpling, rash, and swelling suspicious for inflammatory breast cancer (IBC) or Paget's disease, immediately obtain bilateral diagnostic mammography with ultrasound, followed by skin/nipple biopsy regardless of imaging results, as these aggressive cancers can be mammographically occult. 1, 2

Initial Clinical Assessment

Distinguish between two critical diagnoses:

• Inflammatory Breast Cancer (IBC): Characterized by dermal edema (peau d'orange), breast erythema involving ≥1/3 of the breast skin with a palpable border to the erythema 1
• Paget's Disease: Presents with nipple excoriation, scaling, or eczema-like changes of the nipple-areolar complex 1, 2

Both conditions represent serious disease requiring urgent evaluation, as IBC accounts for 1-6% of breast cancers and is highly aggressive 1

Diagnostic Imaging Protocol

Mandatory First-Line Imaging

Obtain bilateral diagnostic mammography with ultrasound immediately, regardless of patient age 1, 2:

• This applies even to women under 30 years, as skin changes override typical age-based imaging algorithms 1, 2
• Mammography may be negative in pure Paget's disease or IBC, so negative imaging does NOT exclude malignancy 2

Advanced Imaging Considerations

Breast MRI is strongly recommended once biopsy confirms Paget's disease 2:

• 80-90% of Paget's cases have associated DCIS or invasive cancer elsewhere in the breast 2
• MRI defines disease extent and identifies additional foci not adjacent to the nipple 2

Tissue Diagnosis Requirements

Critical Principle: Clinical Suspicion Trumps Imaging

Proceed to biopsy based on clinical findings even if imaging shows BI-RADS 1-3 (negative/benign/probably benign) 1, 3, 2:

• Skin changes indicating IBC or Paget's disease mandate tissue diagnosis regardless of mammographic findings 1, 2

Biopsy Technique Based on Imaging Results

For BI-RADS 1-3 imaging with suspicious skin/nipple changes:

• Perform punch biopsy of the affected skin or full-thickness surgical biopsy of the nipple-areolar complex including epidermis 1, 2
• For suspected Paget's disease, the biopsy must include at least a portion of the clinically involved nipple-areolar complex 2

For BI-RADS 4-5 imaging findings:

• Perform core needle biopsy (preferred) of any suspicious mass or architectural distortion 1, 2
• Add punch biopsy of skin/nipple if surface changes are present 2

Pathology Requirements

Core needle biopsy is mandatory before any treatment to:

• Confirm invasive disease versus in situ carcinoma 1
• Assess biomarkers (ER, PgR, HER-2, Ki67) for treatment planning 1
• Place a marker clip at the biopsy site to ensure correct surgical resection 1

Management of Discordant Results

If biopsy shows benign pathology but clinical suspicion remains high:

• Repeat imaging to confirm the biopsy targeted the correct area 4
• Obtain additional tissue sampling through repeat core biopsy or proceed directly to surgical excision 4
• Consult a breast specialist for reassessment 2

This represents a critical discordance pattern where benign pathology from highly suspicious clinical findings requires escalation 4

Staging Workup

Once malignancy is confirmed, complete the diagnostic workup per ESMO guidelines 1:

• Full blood count, liver and renal function tests, alkaline phosphatase, calcium levels 1
• Assess menopausal status (measure serum estradiol and FSH if uncertain) 1
• Cardiac function evaluation (echocardiogram or MUGA scan) if anthracyclines or trastuzumab are planned 1
• Physical examination for distant metastases; additional imaging only if locally advanced or symptomatic 1

Common Pitfalls to Avoid

Do not mistake Paget's disease for benign eczema or dermatitis 2:

• If uncertain, a short trial of topical steroids may be considered, but this should not delay diagnostic evaluation 2
• When in doubt, perform biopsy rather than observe 2

Do not rely on negative mammography to exclude IBC or Paget's disease 2:

• These conditions can be mammographically occult 2
• Clinical diagnosis of IBC is based on physical findings, not imaging 1

Do not observe without tissue diagnosis in women ≥30 years with suspicious clinical findings 1, 3:

• Observation is never appropriate when skin changes suggest IBC or Paget's disease 1