Paget's disease of the breast, also known as mammary Paget's disease, is a rare dermatological manifestation typically linked to underlying breast cancer. First identified by Sir James Paget in 1874, this condition accounts for 1 to 4% of all breast cancer cases. It is almost invariably associated with underlying breast cancer, with 92% to 100% of patients having concurrent malignancies.

Paget's Disease of the Breast

Signs and Symptoms

Paget's disease of the breast primarily affects the nipple and areola, usually starting at the nipple and spreading outward. Symptoms often wax and wane and typically affect only one breast. Key symptoms include:

• Skin changes: An eczema-like rash is usually the first symptom, with the nipple and areola appearing red, itchy, or tingly. Over time, the skin may become flaky, scaly, or thickened.
• Nipple discharge: Discharge, which may be yellow or bloody, can ooze from the nipple.
• Nipple changes: Inversion of the nipple may occur.
• Breast changes: Palpable lumps or masses may be present, along with redness, oozing, crusting, and sores that do not heal.

Patients often experience symptoms for several months before a diagnosis is made, as the condition is sometimes mistaken for minor contact dermatitis or eczema.

Pathophysiology

Paget's disease is characterised by the presence of Paget cells, which are large cells with clear cytoplasm and eccentric, hyperchromic nuclei dispersed throughout the epidermis. The leading theory of pathogenesis is the migratory theory, where ductal carcinoma in situ (DCIS) cancerous cells migrate through the lactiferous ducts to the nipple, disrupting the epithelial barrier and causing fluid accumulation and crusting of the nipple and areola.

Diagnosis

Diagnosis is challenging due to the disease's similarity to dermatitis and eczema. However, Paget's disease typically begins at the nipple and spreads outward, unlike eczema, which usually starts at the areola. Additionally, eczema usually responds to topical steroids, whereas Paget's disease does not.

Common diagnostic steps include:

• Physical examination: Assessment of the nipple and areola for skin changes and palpation of the breast and armpit for lumps.
• Mammogram and biopsy: A biopsy involves examining a tissue sample under a microscope to identify Paget cells using immunohistochemistry.
• Nipple discharge analysis and ultrasound: Less commonly, nipple discharge may be examined, and an ultrasound may be performed if mammography is inconclusive.

Treatment

Treatment varies based on the type and stage of the underlying breast cancer. Management often involves surgical intervention, such as a lumpectomy or mastectomy, accompanied by chemotherapy and/or radiotherapy.

• Breast-conserving surgery: This approach is used when the disease has not spread beyond the nipple, involving removal of the cancerous area while preserving the rest of the breast. Adjuvant radiation therapy is typically employed post-surgery.
• Mastectomy: For cases with underlying invasive breast cancer, a radical mastectomy may be performed, removing the breast, chest muscle lining, and affected lymph nodes. In noninvasive cases, a simple mastectomy, involving only the breast and chest muscle lining, is performed.

Prognosis

Prognosis is influenced by the presence of a palpable mass, lymph node involvement, and underlying metastatic cancer. The specific presence of Paget's disease does not independently affect prognosis in the context of underlying breast cancer. Patients without underlying breast cancer have a 5-year relative survival rate of 82.6%.

Epidemiology

Paget's disease of the breast is predominantly diagnosed in patients over the age of 50, with an average age at diagnosis of 57. It is rare in both women and men but is more commonly observed in women.

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Self-assessment MCQs (single best answer)

What is the primary area affected by Paget's disease of the breast?

What percentage of breast cancer cases does Paget's disease account for?

Which of the following is NOT a typical symptom of Paget's disease of the breast?

What is the leading theory of pathogenesis for Paget's disease of the breast?

Which diagnostic method is specifically used to identify Paget cells?

Paget's disease of the breast does not respond to which of the following treatments?

In the context of treatment, what does a simple mastectomy involve?

What age group is predominantly diagnosed with Paget's disease of the breast?

What is the 5-year relative survival rate for patients without underlying breast cancer?

Which of the following is a significant indicator influencing the prognosis of Paget's disease of the breast?