Disease patterns in pediatric classical Hodgkin lymphoma: a report from a developing area in Brazil.

Epidemiological patterns established about 20 years ago, divided classical Hodgkin lymphoma (cHL) in three entities with regard to Epstein-Barr virus (EBV) status and histological subtypes and suggested different epidemiological patterns associated with degree of economic development. Here, we investigated histopathological features and EBV association in 100 consecutive pediatric cHL cases occurring in Rio de Janeiro (Brazil). Age at diagnosis ranged from 3 to 18 years (median 14 years) with 27% of cases ≤10 years. Unexpectedly, we did not observe an early childhood peak with most cases occurring in the >10 years age group. Nodular sclerosis (NS) was the most frequent subtype (69%) and was more frequently observed in the >10 years age group, followed by mixed cellularity (MC, 23%) which was distributed equally between age groups. EBV was identified in 44.8% of cases, without preferential association with age groups (≤10 years vs. >10 years). MC cases were independently associated with EBV infection of tumour cells (p = 0.045) and with a CD4/CD20 ratio <1 in the microenvironment (p = 0.014). Our results suggest that a gradual shift from childhood peak to early adulthood peak may be observed in developing regions. The development of MC subtype may result from early exposure to EBV in the context of an impaired immune system reflected by a CD4/CD20 ratio <1. Conversely, it is possible that NS originates predominantly in the context of a better immune response against EBV and/or tumour antigens expressed in the neoplastic cells.