The FOXP1 transcription factor is expressed in the majority of follicular lymphomas but is rarely expressed in classical and lymphocyte predominant Hodgkin's lymphoma.

The expression of the FOXP1 forkhead/winged helix transcription factor has been investigated in normal and neoplastic lymphoid tissues using the FOXP1-specific monoclonal antibody, JC12. Using single and double immunoenzymatic staining, FOXP1 expression has been studied in a series of classical and lymphocyte predominant Hodgkin's lymphomas, follicle centre lymphomas and Hodgkin's lymphoma-derived cell lines. Neoplastic cells in the majority of classical and lymphocyte predominant Hodgkin's lymphoma were FOXP1-negative. In two cases of classical Hodgkin's lymphoma, the tumour cells showed mislocalisation of FOXP1 to the cytoplasm, while in one case of lymphocyte predominant Hodgkin's lymphoma, and in the Hodgkin's lymphoma cell line KMH2, scattered tumour cells showed nuclear expression of FOXP1. In contrast, the tumour cells in the majority of follicle centre lymphomas showed strong nuclear FOXP1 reactivity. Double labelling studies of lymphoid tissue indicated that a variable proportion of CD20-positive germinal centre B cells express FOXP1 while the vast majority of CD30-positive cells are FOXP1-negative. The heterogeneity of FOXP1 expression in germinal centre-derived lymphomas, may have more to do with the transforming events underlying these distinct types of lymphoma than with their common origin.