The most specific immunohistochemical marker to rule out invasive ductal carcinoma would be?: (A) Ki-67, (B) p 63, (C) Desmin, (D) HER 2 / neu
Answer is B. p63 is a marker for myoepithelial cells. When neoplastic cells are identified outside the myoepithelial layer around the ducts, the lesion is said to be invasive. So p63 is most specific marker.