Case Study 46 Julia Kofler, M.D.

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.

Question 1 T1 T1 with contrast

Answer Minimally contrast-enhancing fourth ventricular mass.

Question 2 What 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?

Answer Subependymoma

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?

Answer WHO 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 8 Some 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?

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