View source for WBR0613

{{WBRQuestion
|QuestionAuthor={{Rim}} (Reviewed by {{SSK}} and {{YD}})
|ExamType=USMLE Step 1
|MainCategory=Pathology
|SubCategory=Neurology
|MainCategory=Pathology
|SubCategory=Neurology
|MainCategory=Pathology
|SubCategory=Neurology
|MainCategory=Pathology
|MainCategory=Pathology
|MainCategory=Pathology
|SubCategory=Neurology
|MainCategory=Pathology
|SubCategory=Neurology
|MainCategory=Pathology
|SubCategory=Neurology
|MainCategory=Pathology
|SubCategory=Neurology
|MainCategory=Pathology
|MainCategory=Pathology
|SubCategory=Neurology
|Prompt=A 10-year-old child is brought to the neurology clinic for worsening chronic headache and gait disturbance.  CT scan demonstrates a well-circumscribed mass in the cerebellum with both solid and cystic components. The tumor is successfully resected and treatment is initiated based on the histopathological findings (shown below). What is the most likely function of the cells from which this tumor arises?

[[Image:Rosenthal fibers.jpeg|350px]]
|Explanation=Given the age of the patient, the subtentorial location of the mass, and the cystic and solid features, pilocytic [[astrocytoma]] is the most likely diagnosis.  Pathology of the tumor reveals [[Rosenthal fibers]] which are eosinophilic corkscrew fibers classically observed in pilocytic astrocytoma tumors. The diagnosis can usually be confirmed with GFAP staining. [[Astrocytes]] play a role in the maintenance of the [[blood brain barrier]], regulation of potassium metabolism and [[reactive gliosis]].

Shown below is an image depicting Rosenthal fibers.

[[Image:Rosenthal fiber arrow.png|350px]]
|AnswerA=Reactive gliosis
|AnswerAExp=[[Astrocytes]] play a role in [[reactive gliosis]].
|AnswerB=Phagocytosis
|AnswerBExp=[[Microglia]] play a role in [[phagocytosis]].
|AnswerC=Myelin production
|AnswerCExp=[[Schwann cells]] and [[oligodendrocytes]] produce myelin.
|AnswerD=Action potential generation
|AnswerDExp=[[Neurons]] are responsible for the generation and propagation of [[action potentials]].
|AnswerE=Production of CSF
|AnswerEExp=[[Ependymal cells]] in the inner lining of the ventricles produce [[CSF]].
|EducationalObjectives=Pilocytic astrocytoma is a tumor arising from astrocytes and usually affects children.  It is commonly located in the posterior fossa, but can be found in the supratentorial area. It is pathologically characterized by the presence of [[Rosenthal fibers]] which are eosinophilic corkscrew fibers.  [[Astrocytes]] play a role in the maintenance of the [[blood brain barrier]], regulation of potassium metabolism and [[reactive gliosis]].
|References=First Aid 2015 page 492
|RightAnswer=A
|WBRKeyword=Pilocytic astrocytoma, Brain tumor, Astrocytes, Reactive glioma
|Approved=No
}}