Case Study 46Julia Kofler, M.D.

Clinical history:

29-year-old man who presented with a history of near syncopal episode, headache and mild ataxia.

Describe the lesion on the following MRI scan.

Question 1

T1 T1 with contrast

Question 1

Minimally contrast-enhancing fourth ventricular mass.

Answer

Question 2What is your differential diagnosis based on the radiologic appearance and location of the lesion?

Answer Subependymoma

Ependymoma

Choroid plexus tumor

Pilocytic astrocytoma

Meningioma

Medulloblastoma

Question 3

Which of the tumors in your differential is least likely to be contrast-enhancing?

AnswerSubependymoma

Question 4

A resection of the tumor was performed. Describe the findings on the permanent section.

Click here to view slide.

Answer Clusters of tumor nuclei in a densely fibrillar

background with large anuclear areas

Mildly pleomorphic nuclei with inconspicuous nucleoli

Variable microcystic changes

Rare calcifications

Hyalinized vessels

Focal intratumoral hemorrhage

No mitoses are seen

Question 5

What is your diagnosis?

Answer

Subependymoma

Question 6

Subependymomas correspond to which WHO grade?

AnswerWHO grade 1

Question 7

Some differences with regard to dominant histologic features have been described for supratentorial and fourth ventricular subependymomas. Name some of these features.

Answer

Supratentorial subependymomas are more prone to microcystic change and are usually not calcified

Fourth ventricular subependymomas are commonly calcified and often lack microcystic change

Question 8Some subependymomas contain a component of ependymoma and are classified as mixed subependymoma/ependymoma.

How common are these mixed tumors?

Answer

About 5-20% of subependymomas have an ependymomatous component

Question 9

What is the prognostic significance of the ependymomatous component in mixed tumors?

Answer

Mixed tumors are graded based on the ependymoma component as WHO grade II or III neoplasms

Question 10

What is the immunohistochemical profile of subependymomas?

AnswerGFAP positive

S100 positive

Vimentin positive

Variable reactivity for neuronal markers of low specificity (NCAM, NSE)

Ki-67 labeling index usually <1%