Breast, Invasive ductal carcinoma, EMA stain

This is an example of invasive ductal carcinoma (IDC) with micropapillary features. The definition of “micropapillary” can differ somewhat depending on the anatomical sites. However, in most cases, including breast, the term refers to small clusters of cells (papilla-like) within clear empty spaces, lacking the fibro-vascular cores. These presumably represent horizontal sections of long, papillary structures.

Pure cases of “micropapillary” carcinoma are rare; rather these areas are often seen admixed with more conventional ductal carcinoma. In the cases that make the 90% cut-off, micropapillary carcinoma is associated with worse survival and very frequent lymph node metastases. While this case did not qualify as “micropapillary carcinoma”, lymph nodes were positive for micrometastatic carcinoma.

This slide shows EMA stain. See related content for H&E stain.