DIAGNOSIS: LYMPHOMATOSIS CEREBRI
Neither the clinical story of rapidly progressive dementia nor the diffuse leukoencephalopathy without gadolinium enhancement on MRI led to a diagnosis of primary central nervous system lymphoma (PCNSL) in this patient. Most PCNSL present with symptoms consistent with single or multiple intracranial mass lesions, and these are contrast enhancing on MRI (4). The diagnosis of Creutzfeldt-Jakob disease initially suggested in our case of rapidly progressive dementia with positivity of 14.3.3 protein in the CSF was not supported by neuroimaging findings and was immediately refuted by microscopic examination of autopsy specimens. Diffuse encephalitis was also considered as a possible diagnosis, but all clinical investigations in this way remained negative. No lesion was noticed at gross examination of the brain, and only microscopic examination permitted identification of scattered lymphomatous cells with cytologic atypia and mitoses on all sections from brain hemispheres, brain stem and cerebellum. Immunopositivity of these tumor cells for CD20 attested their B phenotype.
A condition to discuss here is intravascular lymphomatosis because this systemic disorder may be revealed by neurologic manifestations including dementia resulting from the occlusion of small arteries of the brain with lymphoma cells (2, 3). The diffuse pattern of infiltration outside the lumens of blood vessels was absolutely different in our case.
In fact, Bakshi et al (1) reported two cases of diffusely infiltrating PCNSL involving much of the cerebral neuraxis and presenting as rapidly progressive dementia. By analogy with gliomatosis cerebri, the authors proposed the term "lymphomatosis cerebri" to qualify such an infiltrating PCNSL. No "lymphomatosis cerebri" has been reported since this first description, but the present observation illustrates this entity should be considered in the differential diagnosis of a rapidly progressive dementia in adults.
Contributed by Anne Vital, MD, PhD; Igor Sibon, MD