UCLA

OBJECTIVES: The 2015 Workshop of the Society for Hematopathology/European Association for Haematopathology submitted small and large B-cell lymphomas (BCLs), including classical Hodgkin lymphoma (CHL), in the context of immunodeficiency. METHODS: Clinicopathologic and molecular features were studied to explore unifying concepts in malignant B-cell proliferations across immunodeficiency settings. RESULTS: Cases submitted to the workshop spanned small BCLs presenting as nodal or extranodal marginal zone lymphoma and lymphoplasmacytic lymphoma, Epstein-Barr virus (EBV) positive in 75% of cases. Submitted large BCLs formed a spectrum from diffuse large B-cell lymphoma (DLBCL) to CHL across immunodeficiency settings. Additional studies demonstrated overexpression of PD-L1 and molecular 9p24 alterations in the large BCL spectrum and across different immunodeficiency settings. CONCLUSIONS: Small BCLs occur in all immunodeficiency settings, and EBV positivity is essential for their recognition as immunodeficiency related. Large BCLs include a spectrum from DLBCL to CHL across all immunodeficiency settings; immunohistochemical and molecular features are suggestive of shared pathogenetic mechanisms involving PD-L1 immune checkpoints.