HGAL protein expression persists in disorders of germinal center dissolution: Potential role of HGAL in the germinal center microenvironment

Human Germinal Center-associated Lymphoma (HGAL) is a germinal center (GC) B-cell marker associated with a favorable outcome in diffuse large B-cell and classic Hodgkin lymphomas (CHL). To test its potential role in GC function, 75 cases involving GC disruption including 23 progressive transformation of germinal centers (PTGC), 25 follicle lysis and 27 Castleman disease (CD) were studied. HGAL protein expression uniformly correlated with GC B-cells in all except a subset of hyaline-vascular CD that showed severe regression of GCs. HGAL staining highlighted dismantled GCs in PTGC, in contrast to weak or absent CD10 and BCL6 staining. In follicle lysis, HGAL staining was comparable to that of CD10, BCL6, and CD21 in highlighting lysed follicles. Our findings show that HGAL protein expression effectively discriminates clusters of GC B-cells in disrupted follicles. Its persistence in disrupted GCs, suggests that it may be necessary for GC maintenance and supports its proposed role of confining B-cells to the GC microenvironment.