OBJECTIVETo explore the clinical and experimental features of acute leukemia (AL) with trisomy 4.

METHODSA retrospective analysis on the clinical and laboratory data of 21 cases of AL with trisomy 4 was performed. Chromosomes were prepared using direct method and/or short-term (24 h) cultures of bone marrow cells. Karyotypic analysis was carried out by using R-banding technique. Thirteen cases were studied by interphase fluorescence in situ hybridization (FISH) by using a chromosome 4-specific alpha -satellite DNA probe labeled by spectrum Green to ascertain the presence of a clone with trisomy 4. Five cases with t (8; 21) revealed by karyotypic analysis were detected by dual-color FISH using t (8; 21) translocation probe to confirm the AML1/ETO rearrangement.

RESULTSAll the patients with AL and trisomy 4 were with de novo AL except two cases with secondary AL. M2 was the most frequent Franch-American-British(FAB) subtype in this series (9/21 cases). The initial leukocyte count more than 10x 10(9)/L was seen in 16 cases. An enlargement of liver, spleen and/or lymph nodes in varying degrees was found in 15 cases. Among 15 cases received immunophenotypic analysis, 11 cases showed CD34 positivity and 6 cases co-expressed myeloid and lymphocyte antigens. Karyotypic analysis disclosed clonal trisomy 4 in 18 cases and one cell with +4 in 3 cases. Isolated trisomy 4 was found in 7 cases, while 14 cases had other abnormalities besides trisomy 4 among which t (8; 21) was found in 8 cases. Dual-color FISH confirmed that all 13 cases including 3 cases having one cell with +4 on karyotypic analysis had clonal trisomy 4. Dual-color FISH confirmed that all 5 cases with t (8; 21) had AML1/ETO rearrangement.

CONCLUSIONAL patients with trisomy 4 have unique clinical and experimental features and a poor prognosis.