Case Study 3Gabrielle Yeaney, M.D.

Question 1A 7-year-old boy with three month history of nausea, vomiting and headaches. Describe the MRI findings (location, enhancement, mass effect).

Axial T1

Axial T2

Axial T1 +contrast

Coronal T1 +contrast

AnswerThere is a discrete midline mass with mixed cystic and solid components within the posterior fossa/region of the fourth ventricle.  Irregular nodular enhancement is identified in the wall and central aspect.  The tumor exerts mass effect on the pons and midbrain.  The lateral and third ventricles are moderately dilated.

Question 2Name at least three tumors that classically show a cystic architecture with a mural nodule.

Answer1.  Pilocytic astrocytoma2.  Ganglion cell tumor/ganglioglioma3.  Pleomorphic xanthoastrocytoma4.  Hemangioblastoma5.  Supratentorial ependymoma

Question 3The pediatric neurosurgeon gives you a biopsy specimen from the posterior fossa for intraoperative diagnosis.  Describe the cytologic features of the smear.

Click here to view slide.

AnswerSmall bland nuclei in a finely fibrillar backgroundBipolar cells with long hair-like processesRosenthal fibersEosinophilic granular bodiesRare mitotic figure(s)Capillaries

Question 4

What is your intraoperative diagnosis? (A. Neoplastic/Defer/Non-neoplastic, B. ________)

AnswerA. Neoplastic

B. Juvenile pilocytic astrocytoma

Question 5Review the permanent section.  What is your final diagnosis?

Click here to view slide.

AnswerJuvenile pilocytic astrocytoma

Question 6What ARCHITECTURAL feature(s) do you observe on permanent section that was not obvious on the smear?

AnswerLoose microcystic areas are seen in addition to the answers listed in the answer for question 3.  These less cellular areas are suggested on the smear but are not as easily appreciated.

Question 7The bipolar astrocytes in this lesion are thought to produce dense eosinophilic aggregates called ____________ on H&E light microscopy.

AnswerRosenthal fibers are usually seen in the compact areas of JPA.  While helpful, they are not required for the diagnosis of JPA, nor are they specific for JPA.

Question 8In this neoplasm in general (not necessarily this case), what histologic feature would be most concerning for more aggressive behavior (higher grade lesion)?

A.Glomeruloid vessels

B.Mild nuclear atypia

C.Brisk mitotic activity

D.Meningeal infiltration

E.All of the above

AnswerThe correct answer is C. JPA may contain glomeruloid vessels, nuclear atypia and meningeal infiltration.  However, mitotic figures should be infrequent, and the Ki-67/MIB-1 labeling rate is usually very low (0-1%).  Extension into the subarachnoid space is common, particularly in lesions of the optic nerve and cerebellum, and is not a sign of aggressive behavior.  Glomeruloid microvascular proliferation, as a solitary feature, is common and is more often present in the cyst wall.  On the other hand, hyperplasia of endothelial cells in larger vessels is rarely seen.  Focal infarct-like necrosis may also be noted.

Question 9Name three CNS neoplasms with eosinophilic granular bodies.

Answer1.  Ganglion cell tumor/ganglioglioma2.  Pilocytic astrocytoma3.  Pleomorphic xanthoastrocytoma