Discussion:

Papillary lesions are not an uncommon finding in the breast. The differential includes: - Intraductal papilloma
- DCIS, papillary type
- DCIS involving an intraductal papilloma (or intraductal papilloma with ADH)
- Encapsulated papillary carcinoma
- Solid papillary carcinoma

The diagnosis rests heavily on the distribution of myoepithelial cells.

Formerly known as intracystic papillary carcinoma.

Myoepithelial cells are absent within the papillae as well as around the periphery of the tumor.

Traditionally see a thick fibrous capsule.

Degree of invasion is a controversial issue.

loss of an intact myoepithelial cell layer may indicate an indolent course of the tumor with “pushing” or “rounded” invasion.

Some regard it to be in a transition stage from in situ to invasive, or possibly a minimally invasive for of low-grade carcinoma.

Currently regarded as a Tis stage tumor.