Pediatric gray zone lymphoma according to the 2022 WHO classification: An Italian cohort study

BackgroundThe 2022 World Health Organization (WHO) classification redefines the concept of gray zone lymphoma (GZL), restricting it in practice to cases of mediastinal/thymic origin (mediastinal gray zone lymphoma, MGZL) with overlapping features between primary mediastinal B-cell lymphoma (PMBCL) and classical Hodgkin lymphoma (CHL). Cases with histological characteristics of GZL but occurring without mediastinal involvement are better classified as diffuse large B-cell lymphoma, not otherwise specified (DLBCL NOS), with few exceptions. ProcedureWe collected clinical and pathological data about all Italian pediatric patients diagnosed with GZL over a 20-year period. ResultsWe identified only four cases of bona fide MGZL. All patients were adolescent and presented with a mediastinal disease, always associated with other nodal involvement. B symptoms and increased levels of both erythrocyte sedimentation rate (ESR) and lactate dehydrogenase (LDH) were observed. Only two patients achieved a first complete remission, suggesting a more aggressive clinical behavior than either PMBCL or CHL. ConclusionProspective studies evaluating prognostic factors and establishing the most effective first-line therapy for MGZL are highly needed.

Automated summary

The 2022 WHO classification redefines gray zone lymphoma (GZL) and restricts it to mediastinal origin cases called mediastinal gray zone lymphoma (MGZL) with overlapping features between primary mediastinal B-cell lymphoma (PMBCL) and classical Hodgkin lymphoma (CHL). Cases without mediastinal involvement are better classified as diffuse large B-cell lymphoma, not otherwise specified (DLBCL NOS). Clinical and pathological data of Italian pediatric patients with GZL were collected over a 20-year period. Only four cases of bona fide MGZL were identified, showing a more aggressive clinical behavior than PMBCL or CHL. Prospective studies are needed to evaluate prognostic factors and establish the most effective first-line therapy for MGZL.