WBR0206

Author	[[PageAuthor::William J Gibson (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Histology, MainCategory::Microbiology, MainCategory::Pathology
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 60-year-old HIV-positive man is brought to the emergency department after experiencing gradual blurring in both eyes for the past 3 days. Upon further investigation, the patient admits that he has been non-compliant with his anti-retroviral therapy. Physical examination is remarkable for vision loss in the left superior quadrants of his visual fields bilaterally. A brain MRI scan of the patient is shown below. Which of the following findings is most likely to be observed on biopsy of this lesion? ]]
Answer A	AnswerA::Monoclonal B-cell proliferation
Answer A Explanation	AnswerAExp::Monoclonal B-cell proliferation is characteristic of primary CNS lymphoma (PCNSL).
Answer B	AnswerB::Protozoan parasite
Answer B Explanation	[[AnswerBExp::Toxoplasma gondii is a protozoan parasite that causes brain abscesses and focal central nervous system disease among HIV-positive patients with CD4 counts < 100 cells/mm3. Distinguishing a PCNSL vs. toxoplasmosis infection can be difficult. First, the majority of PCNSL are solitary lesions (65%), whereas cerebral toxoplasmosis typically present with multiple foci of disease (86%). Although brain MRI in PCNSL may demonstrate a ring-enhancing lesion similar to cerebral toxoplasmosis, PCNSL lesion is usually larger and is more likely to appear uniformly-enhanced on MRI. Finally, the clinical presentation may be helpful to distinguish both diseases. In the case, the patient has no fever, constitutional symptoms, or epilepsy due to encephalitis.]]
Answer C	AnswerC::Reactive gliosis and vascular proliferation
Answer C Explanation	AnswerCExp::Reactive gliosis and vascular proliferation is the typical histological appearance of a glial scar that appears 1-2 weeks following ischemic stroke.
Answer D	AnswerD::Yeast with narrow-based budding that stains positively with india ink
Answer D Explanation	[[AnswerDExp::Cryptococcus neoformans is a yeast with narrow-based budding that stain positively with india ink. It is a cause of meningioencephalitis in HIV patients with CD4 counts < 50 cells/mm3. Patients infected with cryptococcal meningitis usually have symptoms of meningitis but no signs of meningitis on physical examination.]]
Answer E	AnswerE::Pseudopalisading pleomorphic cells
Answer E Explanation	[[AnswerEExp::Pseudopalisading pleomorphic cells that stain positively for GFAP are characteristic of glioblastoma multiforme (GBM), a highly malignant brain tumor of adults. GBM often crosses the corpus callosum (butterfly glioma) and shows areas of necrosis and hemorrhage on brain MRI.]]
Right Answer	RightAnswer::A
Explanation	[[Explanation::Primary CNS Lymphoma (PCNSL) is a primary intracranial form of extranodal non-Hodgkin's lymphoma that commonly affects patients with AIDS and other immunosuppressive conditions. Non-AIDS patients with post-transplant lymphoproliferation (PTLD) may develop PCNSL that is EBV-induced, where EBV is characteristically identified in CSF of these patients. Common manifestations PCNSL include headache due to increase intracranial pressure, cognitive dysfunction, personality changes, and disorientation. Physical examination is usually remarkable for motor impairment and abnormal findings on ophthalmological exam. In fact, PCNSL is a unique tumor that may manifest with ophthalmological manifestations (10%) because it involves the vitreous, the retina, and the optic nerve, as well as it produces a mass effect that may result in visual changes. In this case, a tumor of the right temporal lobe has disrupted Meyer’s loop causing the visual field defect. Meyer’s loop is a collection of axons from relay neurons in the lateral geniculate nucleus that carry visual information corresponding to the superior lateral visual field to the visual cortex. PCNSL may be visualized by brain MRI, which often shows a single (65%) or multiple (35%) lesions, most of which are greater than 15 mm and attached to the meninges or the subarachnoid space. Patients diagnosed with PCNSL should undergo further work-up for staging and to identify possible infiltration of the disease. Cerebrospinal fluid (CSF) analysis and PCR amplification may help in the diagnosis, since patients often have elevated levels of monoclonal B cells with CD19, CD20, and CD79a positivity. The diagnosis of PCNSL is made by biopsy of the intracranial lesion(s). Since the majority of PCNSL are B-cell lymphomas of germinal B-cell origin, the most likely finding on biopsy is the presence of monoclonal B-cell proliferation. Although low-dose steroid therapy may provide symptomatic relief, steroids may significantly alter the results of the biopsy and yield false-negative findings, which is why steroid therapy needs to be temporarily discontinued prior to biopsy. The mainstay of therapy of PCNSL is anti-retroviral therapy for HIV-positive patients, along with high-dose methotrexate (MTX)-based polychemotherapy with either deferred radiation or autologous stem cell rescue. Radiotherapy has been associated with severe long-term neurotoxicity, and surgery was associated with worse clinical outcomes. Primary CNS lymphoma. Note the solitary subependymal lesion. Cerebral toxoplasmosis. Note the multiple ring-enhancing lesions which fill the basal ganglia. Educational Objective: Primary CNS lymphomas can affect AIDS patients; they cause focal neurological defects and appear as single, uniformly enhancing masses on MRI. References: "Primary CNS Lymphoma, MRI, T1 axial" by user:Tdvorak, licensed under the Creative Commons, terms of GNU Free Documentation License v.1.2 (Image) Kuker W, Nagele T, Korfel A, et al. Primary central nervous system lymphoma (PCNSL): MRI features at presentation in 100 patients. J Neurooncol. 2005;72:169-77. Schlegel U. Primary CNS lymphoma. Ther Adv Neurol Disord. 2009;2(2):93-104. First Aid 2014 page 169]]
Approved	Approved::Yes
Keyword	WBRKeyword::Brain, WBRKeyword::Cancer, WBRKeyword::Intracranial tumor, WBRKeyword::Lymphoma, WBRKeyword::Brain tumor, WBRKeyword::HIV, WBRKeyword::AIDS, WBRKeyword::Primary CNS lymphoma, WBRKeyword::PCNSL, WBRKeyword::Non-Hodgkin's lymphoma, WBRKeyword::NHL, WBRKeyword::HIV-positive
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