Clayton Wiley MD/PhD Question 1 46-year-old male with mental status change and rightsided hemiparesis. Describe the MRI findings (location, enhancement, mass effect). Axial T1 pre and post contrast Axial T2/ FLAIR/ T1 post-contrast Question 2 Give a differential diagnosis based on MRI/ age. Answer • • • • • Lymphoma PML Atypical infection Glioma Imaging features are not consistent with toxoplasmosis or pyogenic abscess (ring-enhancing lesion). Question 3 Describe the cytologic features of the smear. Click here to view slide. Question 4 What additional history might be ascertained to refine the differential diagnosis? Answer Clinical signs of infection. Is this patient immunosuppressed, HIV-positive? Blood analysis? Was CSF culture/ PCR done? Question 5 The surgeon tells you that this patient has a known diagnosis of HIV with a CD4 count of 64. Stereotactic biopsies of the left cerebral white matter are given to you on saline moistened Telfa. You perform a smear the tissue on a glass slide. What is your intraoperative diagnosis? Click here to view slide. Question 6 The surgeon thanks you for your assessment and indicates that s/he is about to close. At this point, before leaving the OR/ frozen room, what should you do? A.Make sure you have enough tissue for diagnosis B.Ask the surgeon if s/he has sent sterile tissue for culture Question 7 Review the H&E paraffin section and give a microscopic description. Click here to view slide. Question 8 What can the Neuropathologist due to further evaluate this lesion? Question 9 You receive the following immunohistochemical study. What is you interpretation? Click here to view slide. Question 10 What is your final diagnosis? Answer Progressive multifocal leukoencephalopathy (PML)—a demyelinating opportunistic infection of the CNS caused by the JC papova virus. Question 11 What cell of the central nervous system is infected in this disease? Answer The oligodendrocyte shows the cytopathic effect in PML.