The Multiple Faces of Nervous System Lymphoma. Atypical Magnetic Resonance Imaging Features and Contribution of the Advanced Imaging.

Primary central nervous system lymphoma (PCNSL) is an uncommon variant of extranodal non-Hodgkin lymphoma, which involves the brain, leptomeninges, eyes, or spinal cord without evidence of systemic disease. In addition to a detailed history and physical examination, the evaluation of patients suspected of having a PCNSL should include a contrast-enhanced magnetic resonance imaging. Occassionaly, PCNSL shows peculiarities on magnetic resonance imaging, which delay the diagnosis and thus the start of treatment. It is essential that radiologists be aware of these less common presentations such as isolated spine or meningeal lymphoma, angiocentric lymphoma, ocular lymphoma, and Epstein-Barr virus-associated lymphoma. Advanced neuroimaging (diffusion and perfusion sequences, spectroscopy-magnetic resonance, and positron emission tomography metabolic imaging) are useful techniques for the differential diagnosis of PCNSL with processes such as brain glioblastoma, multiple sclerosis, and metastases and brain abscesses, especially in atypical presentations. In this article, a review of unusual radiological findings for PCNSL in immunocompetent patients is made, highlighting the usefulness of functional and metabolic imaging for establishing an early presumptive diagnosis, which reduces delays in treatment.