HDAC9 and primary cutaneous T-cell non-Hodgkin lymphoma: Several HDAC inhibitors are approved for the treatment of hematologic malignancies, including belinostat for peripheral T cell lymphoma (PTCL), panobinostat for multiple myeloma, vorinostat for cutaneous T cell lymphoma (CTCL) and romidepsin for both CTCL and PTCL.