To date, four HDAC inhibitors (panobinostat, romidepsin, heliostat, and vorinostat) have been approved by the United States Food and Drug Administration for the treatment of hematological malignancies, such as cutaneous T-cell lymphoma, peripheral T-cell lymphoma, and multiple myeloma [35–39]. The gene discussed is HDAC9; the disease is primary cutaneous T-cell non-Hodgkin lymphoma.