Expression of CD2 in Acute Promyelocytic Leukemia Correlates with Short Form of PML-RARα Transcripts and Poorer Prognosis

We studied the immunophenotype of 100 cases of acute promyelocytic leukemia (APL) with cytogenetic evidence of t(15;17)(q22;q21), 72 hypergranular (M3) and 28 microgranular (M3v), and correlated the results with molecular and clinical features. Most neoplasms (75/100 [75%]) had a typical immunophenotype: CD13+CD33+CD34-HLA-DR-. CD64, CD2, CD34, and HLA-DR were expressed in 27% (24/88), 23% (22/94), 21% (21/100), and 9% (9/98), respectively. CD34 expression was restricted to M3v; HLA-DR and CD2 were expressed more often in M3v than in M3 (P < .001). PML-RARα fusion transcripts were detected by reverse transcriptase-polymerase chain reaction in all 70 patients assessed. The short form of PML-RARα transcripts was found more frequently in M3v (P < .002) and CD2 + APL (P < .0001) than in M3 and CD2- APL, respectively. The median follow-up was 128 weeks. CD2+ APL was associated significantly with leukocytosis (P = .004), shorter complete remission duration (P =.03), and a trend toward shorter overall survival (P =.07) than CD2- APL. Overall survival for M3v vs M3 (P = .68) and short vs long transcripts (P = .21) was not significantly different. Immunophenotyping is useful for predicting the biologic and clinical behavior of APL.