1. Case Study 17 Gabrielle Yeaney, M.D.

2. 17-year-old female with no past medical history. Describe the MRI findings (location, enhancement, mass effect). Question 1

3. Axial T1 T1 post contrast FLAIR

4. Coronal T1 post contrast

5. The ventricular system is normal in size and configuration. In the midline inferior aspect of the 4th ventricle, there is a nodular mass which demonstrates slight T2 prolongation and avidly enhances. There is no adjacent T2 signal abnormality, and this therefore likely is representative of an intraventricular mass lesion. Answer

6. Question 2 What is your differential diagnosis for this enhancing 4th ventricular lesion based on MRI/ age?

7. Answer Choroid plexus papilloma; Ependymoma; Subependymoma (most don’t enhance); Meningioma

8. Question 3 A suboccipital craniectomy is performed for removal of the 4th ventricular mass. Describe the cytologic features of the smear. Click here to view slide.here

9. Answer The smear shows papillae and cohesive clusters of monomorphic epithelioid cells with round regular nuclei. No mitotic figures are seen.

10. Question 4 What is your intraoperative diagnosis? (A. Neoplastic/Defer/Non-neoplastic, B. ______)

11. Answer A. Neoplastic B. Choroid plexus tumor

12. Question 5 Review the permanent section. What are the histologic characteristics that separate is neoplasm from normal choroid plexus? Click here to view slide.here

13. Answer CP papilloma epithelium shows a flat surface (instead of hobnail/ cobblestone), cell crowding, and increased N:C ratio.

14. Question 6 Not that IHC is necessary, but for educational purposes the following stains were obtained. Give your interpretation. Click here to view slides.here

15. Answer Tumor cells strongly and diffusely express CAM5.2, S-100 and prealbumin (transthyretin). There is rare GFAP reactivity. Note: Papillomas occasionally have cells with long tapering processes and focal glial differentiation.

16. Question 7 How is atypical choroid plexus papilloma defined?

17. Answer 2 or more mitotic figs per 10 HPF

18. Question 8 What age group is usually affected by choroid plexus carcinoma? What location is favored?

19. Answer Children; lateral ventricles—Another tumor with similar histology and clinical presentation is atypical teratoid rhabdoid tumor. AT/RT would be EMA positive, INI-1 negative in tumor nuclei (although reports exist that some CP carcinomas are INI-1 negative as well)

20. Question 9 What is Aicardi syndrome?

21. Answer Aicardi syndrome is an X-linked disorder including psychomotor retardation, infantile spasm, corpus callosum agenesis and chorioretinal abnormalities. Cases of choroid plexus papilloma have been reported in association with Aicardi syndrome. Flexion spasms in the infant represent the usual mode of clinical presentation. The chorioretinal abnormality is in the form of lacunae.