A 13-Year Review of Non-Diffuse Large B Cell Lymphomas of the Central Nervous System at a Tertiary Hospital: A Case Series Study.

Non-diffuse large B-cell lymphomas (non-DLBCL) of the central nervous system (CNS) are rare and diagnostically challenging. This study aims to characterize the clinical, radiological, and pathological features of non-DLBCL CNS lymphomas diagnosed at a tertiary care center over 13 years, highlighting diagnostic pitfalls. A retrospective review was conducted of non-DLBCL CNS lymphoma cases diagnosed at Sunnybrook Health Sciences Centre, Toronto, from 2010 to 2022. Clinical, demographic, and radiological data were extracted from medical records. Imaging was reviewed by a neuroradiologist, and histopathological slides and molecular data were re-evaluated by a pathology team. Additional tests were performed to update classifications per the 5th edition of the WHO Classification of Haematolymphoid Tumors. Seventeen cases were identified (11 males, 6 females; age 38-76), compared to 72 DLBCL cases during the same period. Nine cases were extra-axial and eight intra-axial. Eight were primary and nine secondary CNS lymphomas. B-cell lymphomas (n = 13) included extra-nodal marginal zone lymphoma (n = 6), follicular lymphoma, mantle cell lymphoma, CLL, intravascular large B-cell lymphoma (n = 2), EBV+ LBCL, and polymorphic PTLD. T-cell lymphomas (n = 4) included PTCL, NOS (n = 2), ALK-negative ALCL, and secondary mycosis fungoides. Imaging revealed four major patterns, and symptoms were largely due to mass effect. This case series emphasizes the considerable heterogeneity of non-DLBCL CNS lymphomas and the diagnostic challenges they present. It highlights key features that can aid recognition and improve diagnostic accuracy for these rare CNS entities. Trial Registration: SUN-5771.