DermatologyTier 1Disease (DEADMAN)

Cutaneous oncology - breast cancer skin changes

Description

Three distinct cutaneous presentations of breast malignancy, each with a different mechanism and prognostic weight
Paget's disease of the nipple - intraepidermal spread of malignant cells into the nipple-areolar epidermis, associated with an underlying ductal carcinoma (in situ or invasive) in the vast majority
Inflammatory breast cancer (IBC) - tumour emboli obstruct dermal lymphatics -> peau d'orange, erythema, warmth - a clinical diagnosis of a highly aggressive cancer, not a true inflammatory/infective process
Cutaneous metastases - direct skin infiltration, including carcinoma en cuirasse (sclerotic, armour-like chest wall induration)

Paget's disease of the nipple - ~1-3% of breast cancers, almost always unilateral, median age ~50-60
Inflammatory breast cancer - rare (~1-5% of breast cancers) but disproportionately responsible for breast cancer mortality given aggressive biology and frequent delayed diagnosis
Cutaneous metastases - most commonly from breast cancer in women (breast is the commonest primary site for skin metastasis overall)

Paget's disease

Malignant ductal cells ("Paget cells") migrate along lactiferous ducts into the epidermis of the nipple
>90% have an associated underlying breast carcinoma (DCIS or invasive) - the nipple change is a marker, not an isolated skin disease

Inflammatory breast cancer

Dermal lymphatic tumour emboli -> lymphatic obstruction -> oedema of the skin around hair follicles -> peau d'orange (orange-peel dimpling)
Rapid onset over weeks, often without a discrete palpable mass - a clinical + pathological diagnosis (dermal lymphatic invasion on skin biopsy supports but is not mandatory)

Cutaneous metastases

Direct local extension (chest wall) or haematogenous/lymphatic spread to distant skin
Carcinoma en cuirasse - diffuse dermal infiltration and fibrosis -> tight, sclerotic, armour-plate-like chest wall skin -> restrictive effect on chest wall movement

Paget's disease

Unilateral eczematous, scaly, crusted nipple/areolar change that fails to respond to topical steroids - the single biggest trap is misdiagnosis as eczema
May involve nipple erosion, itching, burning, nipple retraction/discharge in advanced disease
Full-thickness nipple punch/wedge biopsy - diagnostic; mammography + breast MRI to assess for the (usual) underlying carcinoma

Inflammatory breast cancer

Clinical diagnosis: rapid-onset erythema/oedema/peau d'orange over >=1/3 of the breast, +/- warmth, +/- palpable mass
Core biopsy of breast parenchyma + skin punch biopsy (dermal lymphatic invasion supportive) - confirms and stages
Staged as T4d, at minimum stage IIIB at diagnosis by definition (skin involvement alone confers locally advanced staging)
Frequently misdiagnosed initially as mastitis/cellulitis - failure to improve on antibiotics within days should prompt biopsy

Cutaneous metastases

New nodules/plaques/induration in a patient with known or prior breast cancer - punch biopsy confirms

A. Paget's disease

Managed as per the underlying breast carcinoma - mastectomy or breast-conserving surgery (excising the nipple-areolar complex) plus radiotherapy, per stage of the associated tumour
Sentinel node biopsy per standard invasive/DCIS staging pathway

B. Inflammatory breast cancer - multimodal, sequenced

Neoadjuvant chemotherapy first (anthracycline/taxane-based +/- anti-HER2 therapy if HER2-positive) -> mastectomy (breast-conserving surgery contraindicated) with axillary staging -> adjuvant radiotherapy -> ongoing systemic/endocrine or anti-HER2 therapy per receptor status
Never start with surgery - upfront surgery in IBC carries poor outcomes; systemic therapy first is standard

C. Cutaneous metastases/carcinoma en cuirasse

Systemic therapy per receptor status and disease burden (endocrine therapy, chemotherapy, targeted anti-HER2/CDK4-6 inhibitors)
Radiotherapy for symptomatic/localised skin disease
Palliative wound care for ulcerating/fungating lesions

Paget's disease - underlying DCIS or invasive ductal carcinoma in the great majority
IBC - triple-negative and HER2-positive subtypes overrepresented; younger age, higher BMI, Black ethnicity described as risk factors in some populations
Cutaneous metastases - advanced/recurrent breast cancer, poor prognostic marker

Paget's disease with an associated invasive carcinoma - prognosis follows that of the underlying tumour stage, not the nipple change itself
Inflammatory breast cancer - most aggressive breast cancer subtype clinically; 5-year survival substantially lower than non-inflammatory locally advanced disease even with modern multimodal therapy
Cutaneous metastases/carcinoma en cuirasse - indicate systemic/advanced disease, generally a poor prognostic sign, management shifts toward disease control and quality of life
Delay to diagnosis is the recurring theme across all three - each is frequently mistaken for a benign dermatological or infective process first

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