Real-world lymphoma cohort in an HIV-endemic setting: cohort design, epidemiological features and impact of implementing novel classification standards

Lymphoma real-world observational data and accurate diagnostic systems are lacking in low-resource HIV-endemic settings. We established a new lymphoma registry to generate internationally comparable, clinically validated data, with up-to-date disease classification. We also describe our findings on aggressive B-cell lymphoma. The descriptive retrospective cohort included patients ≥ 13 years of age newly diagnosed with lymphoma from 2005 to 2020. Patients were enrolled at a single site in a registry with hierarchical groupings to capture, interrogate, and subtype lymphoma diagnoses. These were standardised on the most recent version of the World Health Organisation Classification of Haematolymphoid Tumours (WHO-HAEM5) and correlated with the novel International Consensus Classification of mature lymphoid neoplasms (ICC). Differences due to nomenclature and diagnostic category were annotated. The cohort consisted of 2354 incident lymphoma cases; 1891 (80.3%) non-Hodgkin lymphoma and 463 (19.7%) Hodgkin lymphoma (HL). Twenty-one lymphoma NOS cases were excluded due to inadequate specimen for standardised subclassification. Overall reclassification according to WHO-HAEM5 was 25.8% (n = 608). Notable nomenclature differences between WHO-HAEM5 and ICC included 44 (1.9%) transformations of indolent B-cell lymphomas; also 857 (36.4%) lymphoid proliferations and lymphomas associated with immune deficiency/dysregulation due to HIV (33.1%) and EBV (31.8%). EBV-association was highest among HL cases, of which 77 (50.3%) were HIV reactive. We report here the impact of adopting international lymphoma classification standards in an HIV-endemic setting. Our findings highlight the persistent prevalence of large B-cell lymphoma, raise concern around inadequate HIV suppression as a potential ongoing driver of disease in our setting, and provide further evidence for EBV-associated HL as a distinct subtype.