1. Case Study 46
Julia Kofler, M.D.

2. Question 1
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.

3. Question 1
T T1 with contrast

4. Answer
Minimally contrast-enhancing fourth ventricular mass.

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

6. Answer Subependymoma Ependymoma Choroid plexus tumor
Pilocytic astrocytoma
Meningioma
Medulloblastoma

7. Question 3
Which of the tumors in your differential is least likely to be contrast-enhancing?

8. Answer
Subependymoma

9. Question 4
A resection of the tumor was performed. Describe the findings on the permanent section. Click here to view slide.

10. 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

11. Question 5
What is your diagnosis?

12. Answer
Subependymoma

13. Question 6
Subependymomas correspond to which WHO grade?

14. Answer
WHO grade 1

15. Question 7
Some differences with regard to dominant histologic features have been described for supratentorial and fourth ventricular subependymomas. Name some of these features.

16. 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

17. Question 8
Some subependymomas contain a component of ependymoma and are classified as mixed subependymoma/ependymoma. How common are these mixed tumors?

18. Answer
About 5-20% of subependymomas have an ependymomatous component

19. Question 9
What is the prognostic significance of the ependymomatous component in mixed tumors?

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

21. Question 10
What is the immunohistochemical profile of subependymomas?

22. Answer GFAP positive S100 positive Vimentin positive
Variable reactivity for neuronal markers of low specificity (NCAM, NSE)
Ki-67 labeling index usually <1%