Aberrant phenotypic expression of CD15 and CD56 identifies poor prognostic acute promyelocytic leukemia patients.

Limited information is available on the relationship between expression of some additional aberrant phenotypic features and outcome of acute promyelocytic leukemia (APL) patients. Here, we set out to assess the frequency of CD15 and CD56 expression, and their prognostic value in a large series of APL patients. One hundred and fourteen adult patients consecutively diagnosed with PML/RAR alpha-positive APL and homogeneously treated with the AIDA induction schedule at a single institution were included in the study. Twelve (10.5%) and 9 (8%) of the 114 patients expressed CD15 and CD56, respectively. CD15 expression identified a subset of patients with a classic morphologic subtype (92%), a prevalent association with a bcrl expression (67%) with an unexpectedly higher frequency of relapses (42% vs 20% for the CD15 patients, p=0.03) and a low overall survival (OS) (median OS at 5 years 58% vs 85% for the CD15 patients, p = 0.01). CD56 expression was detected only in patients with a classic morphologic subtype, a prevalent bcr3 expression (67%), high incidence of differentiation syndrome (55%), higher frequency of relapse (34% vs 20% for the CD56 population, p = 0.04) and a low OS (60% vs 85% for the CD56 population p = 0.02). We hereby confirm the negative prognostic value of CD56 and we show that the same applies also to cases expressing CD15. These aberrant markers may be considered for the refinement of risk-adapted therapeutic strategies in APL patients.