Breast: Practice Question

A breast lesion with papillary architecture is located within a duct. Myoepithelial markers are positive on the duct periphery but negative in the papillae. What is the most likely diagnosis?
  1. DCIS with papillary architecture
  2. Solid papillary carcinoma
  3. Encapsulated papillary carcinoma
  4. Papilloma with atypical ductal hyperplasia
  5. Intraductal papilloma
Show Answer and Explanations

DCIS with papillary architecture — Correct answer

Correct. DCIS with papillary architecture, also known as papillary DCIS is the most likely diagnosis. As with all DCIS, native duct wall retains myoepithelial cells, but the neoplastic structures (in this case, the papillae) do not contain myoepithelial cells.

Solid papillary carcinoma

Incorrect. Solid papillary carcinoma have no myoepithelial cells. It has solid papillary architecture and is not encapsulated.

Encapsulated papillary carcinoma

Incorrect. Encapsulated papillary carcinoma have no myoepithelial cells at the periphery OR at the papillae. It differs from solid papillary carcinoma in that it has a fibrous capsule.

Papilloma with atypical ductal hyperplasia

Incorrect. Papillomas with ADH have myoepithelial cells lining the duct periphery, and lining some of the papillae except for the region of ADH.

Intraductal papilloma

Incorrect. Intraductal papillomas have myoepithelial cells lining the duct periphery AND the papillae.

Summary

Summary: Myoepithelial markers are key in the diagnosis of papillary breast lesions. Papillary DCIS (DCIS with papillary architecture) has myoepithelial cells lining the duct but not in the papillae. Intraductal papillomas have myoepithelial cells lining the duct AND the papillae. Encapsulated papillary carcinoma and solid papillary carcinoma have no myoepithelial cells at the periphery OR at the papillae. Papillomas with ADH have myoepithelial cells lining the duct periphery, and lining some of the papillae except for the region of ADH.
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