117 Primary Central Nervous System Lymphoma in Puerto Rican Patients: A Case Series and Diagnostic Profile

Introduction/Objective Primary central nervous system lymphoma (PCNSL) is a rare, aggressive extranodal non-Hodgkin lymphoma confined to the brain, spinal cord, leptomeninges, or eyes, accounting for approximately 4% of intracranial tumors and 4–6% of extranodal lymphomas. Most PCNSLs are diffuse large B-cell lymphomas (DLBCL), typically affecting older adults. Their clinical presentation varies, reflecting involvement of distinct CNS regions, and may include cognitive decline, focal neurological deficits, or neuropsychiatric symptoms. Diagnosis relies on clinical suspicion, neuroimaging, and histopathologic confirmation. Molecular and immunophenotypic features, including double expression of MYC and BCL2, carry prognostic implications. Despite growing understanding of PCNSL, literature on its presentation and biology in Hispanic populations—especially in the Caribbean—is limited. This is particularly relevant in resource-constrained environments, where ancillary studies may be limited and timely diagnosis is critical. This case series highlights the clinical, histopathological, and molecular characteristics of PCNSL in three Puerto Rican patients, contributing to the broader understanding of this rare malignancy in underserved populations and underscoring the importance of comprehensive immunophenotyping in diagnosis and risk stratification. Methods/Case Report A retrospective search of the laboratory information system (LIS) was conducted at two affiliated pathology laboratories: ASEM Pathology Laboratory and the Department of Pathology at the University of Puerto Rico Medical Sciences Campus. Brain biopsy and resection specimens with a diagnosis of lymphoma between June and December 2024 were reviewed. Inclusion criteria were cases with histopathologic and immunophenotypic confirmation of primary CNS lymphoma (PCNSL), defined as lymphoma limited to the CNS without systemic involvement at diagnosis. Histological evaluation included H&E staining and reticulin special stain. Immunohistochemistry (IHC) was used to assess expression of CD20, CD10, BCL6, MUM1, BCL2, MYC, and Ki-67 and classification was performed using the Hans algorithm. FISH analysis for MYC, BCL2, and BCL6 gene rearrangements was performed on available samples. Clinical data, including age, sex, presentation, imaging findings, and relevant medical history, were extracted from pathology reports and medical records, in consultation with the neurosurgery department. Results NA Conclusion All three patients in this series were diagnosed with diffuse large B-cell lymphoma (DLBCL), non-germinal center subtype, based on immunophenotypic features. Two cases demonstrated double expression of MYC and BCL2 by IHC, a profile associated with poorer prognosis, but FISH studies were negative for MYC, BCL2, and BCL6 rearrangements. These findings reinforce the diagnostic and prognostic value of IHC, particularly in settings where molecular testing may be limited or when translocations are not detected. The classic perivascular growth pattern and reticulin staining supported the histologic diagnosis. This case series adds to the limited literature on PCNSL in Hispanic and Caribbean populations, contributing valuable demographic, diagnostic, and molecular insights. Broader recognition of this entity’s presentation and pathology in underrepresented groups may improve early diagnosis, risk stratification, and ultimately, patient outcomes.