WBR0613

Author	[[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Serge Korjian M.D. and Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Neurology
Prompt	[[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? ]]
Answer A	AnswerA::Reactive gliosis
Answer A Explanation	[[AnswerAExp::Astrocytes play a role in reactive gliosis.]]
Answer B	AnswerB::Phagocytosis
Answer B Explanation	[[AnswerBExp::Microglia play a role in phagocytosis.]]
Answer C	AnswerC::Myelin production
Answer C Explanation	[[AnswerCExp::Schwann cells and oligodendrocytes produce myelin.]]
Answer D	AnswerD::Action potential generation
Answer D Explanation	[[AnswerDExp::Neurons are responsible for the generation and propagation of action potentials.]]
Answer E	AnswerE::Production of CSF
Answer E Explanation	[[AnswerEExp::Ependymal cells in the inner lining of the ventricles produce CSF.]]
Right Answer	RightAnswer::A
Explanation	[[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. Educational Objective: 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]]
Approved	Approved::No
Keyword	WBRKeyword::Pilocytic astrocytoma, WBRKeyword::Brain tumor, WBRKeyword::Astrocytes, WBRKeyword::Reactive glioma
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::