Spectral karyotyping refined the identification of a der(Y)t(Y;1)(q11.1 or.2;q12) in the blast cells of a patient with atypical chronic myeloid leukemia.

We report a case of atypical chronic myeloid leukemia who showed leukocytosis with immature granulocytes and dysplastic features but no monocytosis or basophilia. Cytogenetic analysis by conventional G-banding showed an abnormal clone, which was interpreted as 46,X,-Y,+der(?)t(?;1)(?;q?1), and no Philadelphia chromosome. Reverse transcription-polymerase chain reaction did not show either major or minor BCR-ABL chimeric mRNA. Spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH) refined the karyotype to 46,X,der(Y)t(Y;1)(q11.1 or.2;q12). The der(Y)t(Y;1) abnormality was reported previously in 9 cases and associated with myelodysplastic syndrome or chronic myeloproliferative disorders. SKY in combination with the standard banding method and FISH may be useful for exploring undefined chromosome abnormalities in hematological disorders.