1 April 2010 – Case of the Week #175
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Thanks to Dr. Julia Braza, Beth Israel Deaconess Medical Center, Boston, Massachusetts (USA), for contributing this case and much of the discussion. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.
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Case of the Week #175
A 70 year old woman presented with confusion, lethargy, short term memory loss, disorientation, and fever. She had a history of CNS vasculitis and a right thalamic CVA.
MRI showed a rounded lesion in the right cerebral peduncle and the right putamen / inferior lateral thalamus. Radiologically it was a homogeneous lesion with slight effacement of the right lateral ventricle. The radiologic differential diagnosis was lymphoma, primary glial neoplasm or subacute infarct. There was no other significant medical history.
A biopsy was obtained.
H&E and reticulin
EBER (in situ hybridization stain for EBV encoded RNA)
What is your diagnosis?
Primary diffuse large B cell lymphoma of the CNS
Primary diffuse large B-cell lymphoma of the central nervous system is a rare tumor that by definition, arises exclusively in the CNS with no obvious lymphoma elsewhere at diagnosis. It represents 5-10% of CNS neoplasms in patients ages 75+ (Hum Path 2003;34:1137). A majority of these neoplasms arise supratentorially within the white matter and in the periventricular area. They may be multifocal and may affect the leptomeninges, but primary leptomeningeal involvement is rare. At diagnosis, 20% have ocular involvement; and 80-90% of these patients develop contralateral tumors and intraparenchymal CNS lesions, with invasion of the subretinal pigment epithelial space and vitreous. Dissemination to extraneural sites such as bone marrow is extremely rare.
Radiologically, these tumors are generally solitary, homogeneously contrast enhancing and usually have no ring enhancement, in contrast to glioblastoma multiforme and metastases.
Clinically, patients usually present with focal neurological deficits, signs of increased intracranial pressure or neuropsychiatric symptoms. Leptomeningeal involvement generally presents with a headache. Intraocular involvement may cause blurred vision or floaters.
Grossly, most central lymphomas are solid, grey, ill-defined, and usually deep-seated. Some travel along white matter tracts and transcend the corpus callosum, like infiltrating gliomas. Histologically, they are widely infiltrating with a perivascular predilection. Most are discohesive, but may occur in a glial meshwork within the CNS. Primary brain lymphomas have scant cytoplasm, high grade nuclei and multiple nucleoli, but less pleomorphism than other high grade CNS tumors. Most primary CNS lymphomas are diffuse large B cell subtype, and are immunoreactive for CD20, CD79a and CD22, but negative for CD3. However, nearly all tumors have a background of reactive T cells that may lead to an erroneous diagnosis of T cell lymphoma. The mitotic index is often > 50%.
Smears show single cells with discrete cell borders, vesicular nuclei, prominent nucleoli and frequent apoptosis.
Treatment includes high-dose methotrexate therapy with or without radiation. Chemotherapy has extended median survival in immunocompetent patients to 44 months (eMedicine). Although tumors can be classified by immunohistochemistry into germinal center and non-germinal center phenotypes, this does not appear to influence prognosis (Neuropathology 2009 Nov 18 [Epub ahead of print], J Neurooncol 2009 Dec 13 [Epub ahead of print]).
Additional references: Neurol India 2009;57:756
Nat Pernick, M.D., President,
and Kara Hamilton, M.S., Associate Medical Editor
30100 Telegraph Road, Suite 408
Bingham Farms, Michigan (USA) 48025
Alternate email: NatPernick@gmail.com