Identification of the BRAF-V600E kinase mutation as the genetic cause of HCL has opened the way, in the relapsed/refractory experimental setting, to targeted and non-myelotoxic effective strategies that are based on inhibition of BRAF with vemurafenib, co-inhibition of BRAF and its target MEK with dabrafenib and trametinib, and BRAF inhibition with vemurafenib combined with anti-CD20 immunotherapy.
We hypothesized that detection of phospho-ERK (pERK) in tissue sections may be a useful marker for diagnosis of HCL. pERK/CD20 double immunostaining was performed on 90 formalin-fixed bone marrow trephine samples affected with small B-cell lymphoproliferative disorders, including 28 cases of HCL. pERK staining was observed in all 28 cases of HCL and in 1 of 62 cases of non-HCL B-cell lymphoproliferative disorders.
The cytochemical, transmission electron microscopy, and surface antigens data (CD3+, CD8+, CD11+, HLA-DR+, CD19-, CD20-) were consistent with a T-cell hairy-cell leukemia.