This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous System, Subject name: Pathology
10 year old child with posterior fossa mass. On biopsy following features were seen. What are these dense eosinophilic fibers marked with arrow? 
Select and explain. 
A. Rosenthal fibers, B. The Alzheimer type II astrocyte, C. Corpora amylacea, D. None
A: Rosenthal fibers
Answer: A: Rosenthal fibers 
Explanation: Ans. (a) Rosenthal fibers*Rosenthal fibers are eosinophilic, corkscrew fibers found in pilocytic astrocytoma, the most common primary brain tumor in children. They contain two heat-shock proteins (aB-crystallin and hsp27) as well as ubiquitin.*They are seen in Alexander disease and, pilocytic astrocytoma.