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
All of the following act as cell adhesion molecules, EXCEPT: 
Select and explain. 
A. Integrin, B. Selectin, C. Cadherin, D. Lecithin
D: Lecithin
Answer: D: Lecithin 
Explanation: Most adhesion proteins, also called CAMs (cell adhesion molecules), can be classified into four main families: immunoglobulin family CAMs, cadherins, integrins, and selectins. Ref: Robbins 8th edition, Chapter 3.