Breast, Epithelial-myoepithelial invasive carcinoma, CK7 stain

Invasive breast carcinoma can have epithelial or myoepithelial (metaplastic) differentiation; however, this mixed form is uncommon. Although a benign adenomyoepithelioma component is not seen in this case, mixed epithelial-myoepithelial carcinoma falls within the same WHO classification group. Some authors suggest that this pattern is analogous to a salivary-type carcinoma. Prognosis and treatment are generally as for a metaplastic carcinoma of the breast with similar grade and biomarker profile.

Sections show a tumor with a solid pattern with irregular borders and large areas of necrosis. The tumor is composed of discohesive epithelioid cells separated by fibrous septae. Cell nuclei are enlarged and pleomorphic and have prominent nucleoli. The mitotic rate is high with multiple atypical mitoses. The majority of cells have ill defined, pale cytoplasm and a minority of cells have dense cytoplasm.

Immunohistochemical staining shows that a majority of the cell population is positive for S100. Immunostaining for CK-7 and p63 shows scattered positivity.

This slide shows CK7 stain. See related content for H&E, S100, and p63 stains.