1. EM of a CNS tumor shows prominent interdigitating processes without a basal lamina. There are well formed desmosome junctions and prominent cytoplasmic inclusions. These findings are most consistent with:

2. EM of an undifferentiated tumor is noted to have long thin microvilli (height to width ~ 10:1). Which of the following tumors is this most consistent with:

3. Based on the findings in the image below for Case #5, which of the following is the best diagnosis?

4. A biopsy from the tongue shows pseudoepitheliomatous hyperplasia with histiocyte like cells underneath, which contain a granular cytoplasm. A diagnosis is suspected and confirmed with S-100 positivity. Which of the following is true with regards to this tumor:

5. An undifferentiated tumor shows prominent profiles of rough endoplasmic reticulum. Which of the following markers would also be positive in this lesion?

6. EM of a CNS tumor showed intracellular lumens lined by microvilli with specialized junctions between cells and glial features. This is most conisistant with which of the following tumors:

7. EM of a tumor shows rhomboid crystalline inclusions. Cytogenetics also showed a t(X;17). These findings are consistent with which of the following neoplasms?

8. Based on the findings in the images below for Case #3, which of the following is the best diagnosis?

9. Based on the findings in the images below for Case #2, which of the following is the best diagnosis?

10. Based on the findings in the images below for Case 1, which of the following is the best diagnosis?

11. A specimen being prepared for electron microscopy should be fixed in:

12. Based on the findings in the images below for Case #4, which of the following is the best diagnosis?

13. EM of an undifferentiated tumor shows microvilli with long filamentous core rootlets (electron dense). This finding suggests which diagnosis: