Paget disease of the breast

Paget disease of the breast, also Paget's disease of the breast, is a thingy seen in the breast... and elsewhere - except bone.

There is also a Paget disease of the bone - just to make things confusing. This is dealt with in the bone article and has nothing (from a pathologic perspective) to do with the Paget disease discussed in this article; these two things just happened to be discovered by the same guy.

Non-bone Paget disease is subdivided into:

1. Mammary Paget disease.
2. Extramammary Paget disease.

Histologically, i.e. under the microscope, the above are essentially identically; however, the associations (and prognosis) are quite different!

Mammary Paget disease

General

• Cells in the epithelium, i.e. skin, that look like they don't belong.
• Associated with underlying breast carcinoma.

Note:

• Extra-mammary Paget's disease is not assoc. with malignancy.

Microscopic

Features:

• Epitheliod morphology (round/ovoid).
• Cells nested or single.
• Clear/pale cytoplasm key feature - may also be eosinophilic.
• Large nucleoli.

Images:

• Paget's disease - low mag. (WC).
• Paget's disease - high mag. (WC).

DDx

• Benign Toker cell hyperplasia.
• Malignant melanoma.
• Bowen disease.
• Nipple (duct) adenoma (clinical DDx).

IHC

Panel:

• S-100 -ve, HMB-45 -ve (both typically +ve in melanoma).
• CK7 +ve
• CEA +ve (-ve in Bowen's disease, -ve in Toker cells).

Additional:

• HER2/neu - usually +ve.
• CK5/6 -ve.
  • Usu. +ve in squamous cell carcinoma.

Extramammary Paget disease

General

• Usually not associated with malignancy.

Microscopic

Features:

• Indistinguishable from mammary paget's disease.
  • See Microscopic section in mammary Paget's disease.

See also

• Breast.
• Invasive breast cancer.