OS according to WHO category among leukemic T-cell tumors. Kaplan-Meier analysis demonstrates a significant difference in disease-specific OS between patients with T-PLL, primary SS, secondary SS, T-LGL leukemia and HSTCL (P = .0002). Ten of 32 patients with primary SS and 1 of 15 patients with T-LGL leukemia had died at last follow-up but some follow-up times were short compared with OS, precluding calculation of a meaningful median survival. Abbreviations are explained in Figure 1.