Primary B Cell Lymphoma of the CNS Mimicking Anti-LGI1 Limbic Encephalitis

Abstract

Limbic encephalitis is a potentially paraneoplastic type of encephalitis mainly involving the limbic system. Recently, diagnostic criteria comprising clinical presentation as well as imaging, laboratory and electrophysiological findings have been established. Here, we show that incipient primary central nervous system lymphoma can closely resemble limbic encephalitis including positive testing for anti-LGI1 antibodies illustrating the need for thorough interpretation of initial laboratory and radiologic findings and tight follow-up examinations.

Keywords: LE; MRI; PCNSL; antibodies; diagnostic criteria.

Figure 1

MRI at initial presentation showing volume and signal increase of the right medial temporal lobe with focal extension to neocortical areas on T2/FLAIR images (a) without contrast enhancement (b,c). In contrast, follow-up MRI showing multiple lesions in axial T2/FLAIR (d) with contrast enhancement (e,f). On histopathological examination, a malignant lymphoid tumor (g) with expression of CD20 (h) and some intermingled reactive CD3-positive lymphocytes (i) was encountered. Ki67/Mib1 proliferation index accounted for 92% (j). All scale bars represent 50 μm.