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
Which is the most important feature to differentiate carcinoma in situ from invasive carcinoma? 
Select and explain. 
A. Metastasis, B. Anaplasia, C. Number of mitotic spindles, D. Breach in basement membrane
D: Breach in basement membrane
Answer: D: Breach in basement membrane 
Explanation: Penetration of basement membrane is the hallmark of invasive carcinoma. In carcinoma in situ basement membrane is not  involved.