Background: Aberrant phenotypes in acute leukemia have variable frequency and their prognostic andpredictive relevance is controversial, despite several reports of clinical significance. Aims: To determinethe prevalence of aberrant antigen expression in acute leukemia, assess clinical relevance and demonstrateimmunophenotype-karyotype correlations. Materials and
Methods: A total of 73 (40 AML and 33 ALL) newlydiagnosed acute leukemia cases presenting to KAMC, Kingdom of Saudi Arabia, were included. Diagnosis wasbased on WHO criteria and FAB classification. Immunophenotyping by flow cytometry, conventional karyotypingand fluorescence in situ hybridization for gene rearrangements were performed.
Results: Aberrant antigens weredetected in 27/40 (67.5%) of AML and in 14/33 (42.4%) in ALL cases. There were statistically significant higherTLC in Ly+ AML than in Ly-AML (p=0.05) and significant higher blast count in ALL with aberrant antigensat presentation and day 14 (p=0.005, 0.046). There was no significant relation to clinical response, relapse freesurvival (RFS) or overall survival (p>0.05), but AML cases expressing ≥2 Ly antigens showed a lower medianRFS than those expressing a single Ly antigen. In AML, CD 56 was expressed in 11/40. CD7 was expressed in7/40, having a significant relation with an unfavorable cytogenetic pattern (p=0.046). CD4 was expressed in 5/40.CD19 was detected in 4/40 AML associated with M2 and t (8; 21). In ALL cases, CD33 was expressed in 7/33and CD13 in 5/33. Regarding T Ag in B-ALL CD2 was expressed in 2 cases and CD56 in 3 cases.
Conclusions:Aberrant antigen expression may be associated with adverse clinical data at presentation. AML cases expressing≥2 Ly antigens may have shorter median RFS. No specific cytogenetic pattern is associated with aberrant antigenexpression but individual antigens may be related to particular cytogenetic patterns. Immunophenotype-karyotypecorrelations need larger studies for confirmation.