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 of the following is not included under diagnostic criteria for NF - 1? 
Select and explain. 
A. Optic glioma, B. Cafe - au - lait macules, C. periungual fibroma, D. Sphenoid dysplasia
B: Cafe - au - lait macules
Answer: B: Cafe - au - lait macules 
Explanation: Periungal fibroma is not included under diagnostic criteria for NF - 1.