This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
The most specific immunohistochemical marker to rule out invasive ductal carcinoma would be? 
Select and explain. 
A. Ki-67, B. p 63, C. Desmin, D. HER 2 / neu
B: p 63
Answer: B: p 63 
Explanation: 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.