Which markers are used to establish the presence or absence of invasive breast carcinoma?

• A. Myoepithelial
• B. EGFR
• C. CK 5/6
• D. HER2

Answer: (A)

Myoepithelial markers are used to determine whether invasive breast carcinoma is present by assessing the myoepithelial cell layer around ducts and lobules. In situ lesions keep an intact myoepithelial layer, so staining shows a continuous ring of myoepithelial cells around the ducts. If the tumor has invaded the surrounding stroma, this layer is disrupted or lacking in the invaded areas, and myoepithelial markers no longer outline the ducts there. Because of this, immunostaining for myoepithelial cells (examples include p63, SMA, calponin, and related markers) directly indicates invasion status.

Markers like EGFR are used to study tumor biology and potential targeted therapies but do not by themselves confirm invasion. CK 5/6 helps classify certain breast cancer subtypes, particularly basal-like features, rather than invasion. HER2 status guides treatment decisions and prognosis, but it does not determine whether tumor cells have invaded the surrounding tissue.