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 reliable single histologic criterion for diagnosis of oral squamous cell carcinoma is: 
Select and explain. 
A. Invasion, B. Degeneration, C. Pleomorphism, D. Encapsulation
A: Invasion
Answer: A: Invasion 
Explanation: None