T-MN is easily distinguished from APL relapse by evaluating hematologic features. (A) Relapse risk was predicted by pretreatment WBC and platelet counts of each patient at APL diagnosis. Patients with APL could be stratified into low-risk (WBC count ≤ 10 × 103/μL, platelet count > 40 × 103/μL), intermediate-risk (WBC count ≤ 10 × 103/μL, platelet count ≤ 40 × 103/μL), and high-risk (WBC count > 10 × 103/μL) groups. The number of patients in high-, intermediate-, and low-risk groups were 21 (25.6%), 40 (48.8%), and 21 (25.6%), respectively, in the disease-free population, whereas they were 5 (50%), 1 (10%), and 4 (40%), respectively, in the relapse patients and 2 (18.2%), 3 (27.3%), and 6 (54.5%), respectively, in the t-MN patients. (B) Overall survival from date of starting chemotherapy for the relapsed APL or t-MN patients after successful APL treatment. Patients with t-MDS-RCMD and patient 78 who were treated without chemotherapy were excluded. (C) Surface-marker analysis of the leukemic cells by the CD45RO gating method. Because of their low blast percentages, t-MDS-RCMD patients were excluded. *Patient 48 and **patient 109 were mixed lineage leukemia with MLL chimera. (D) APL relapse and t-MN were distinguished by CD34/HLA-DR expression patterns. (E) Clinical course of a 69-year-old man. The patient developed APL in 2009, although he had a normal blood count until 2008. Eight months after starting the treatment for APL with ATRA and chemotherapy, the patient showed persistent thrombocytopenia and trilineage dysplasia (megaloblastic changes of erythroblasts, decreased granules of granulocytes, and micromegakaryocytes), and he was diagnosed as t-MN.
