Paget Disease of the Breast
A rare manifestation of breast carcinoma characterized by malignant cells extending from an underlying ductal carcinoma (usually DCIS) into the nipple skin.
1. Clinical Presentation
- Classic Symptoms: Erythematous, scaly, crusting plaque on the nipple or areola.
- Common Misdiagnosis: Often mistaken for eczema or dermatitis, leading to delayed diagnosis. Any persistent nipple lesion should be biopsied.
2. Pathological Features
| Feature | Description |
|---|---|
| Paget Cells | Large, pleomorphic malignant cells with abundant clear cytoplasm found within the epidermis. |
| Underlying Lesion | Associated with an underlying **DCIS** (most common) or invasive ductal carcinoma. |
3. Exam Must-Knows
- Prognosis: Depends on the underlying breast cancer (DCIS vs. invasive carcinoma).
- Distinction: Unlike Paget disease of the bone (which involves osteoclasts and bone deformities), this is purely a dermatological manifestation of underlying breast malignancy.
Pathology Board Hint: For test questions, remember that Paget disease of the breast is not just a skin condition. Always look for the associated underlying DCIS. If a patient presents with a chronic, non-healing nipple lesion that looks like eczema but does not respond to topical steroids, perform a biopsy.