<prompt> The most specific immunohistochemical marker to rule out invasive ductal carcinoma would be?Ki-67p 63DesminHER 2 neu  <response>: 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. 