Breast Microinvasion Cocktail contains which markers?

• A. p63 + Cytokeratin 8/18
• B. Cytokeratin 14 + 18
• C. Cytokeratin 5/6 only
• D. Cytokeratin 5/6 + p63 + Cytokeratin 8/18

Answer: (D)

The test is about using an IHC cocktail that lets you see both the myoepithelial layer and the tumor epithelial cells to assess microinvasion in breast tissue. For this purpose you want markers that highlight the myoepithelium (the layer you look for to determine if invasion has occurred) and markers that label the epithelial tumor cells themselves. Cytokeratin 5/6 and p63 are used to identify myoepithelial/basal cells—p63 is a nuclear marker, while CK5/6 is a basal cytokeratin. Cytokeratin 8/18 marks luminal epithelial cells, which include the tumor cells you’re trying to delineate. Using all three together lets you visualize the intact myoepithelium around ducts and simultaneously outline the epithelial tumor component, enabling accurate assessment of invasion. That combination—CK5/6 plus p63 plus CK8/18—provides the most informative staining for microinvasion. Without the luminal marker you’d miss the tumor cells; without the myoepithelial markers you’d lose the invasion context.