Evidence for deletion of 9q as a two-step process in chronic myeloid leukemia.

Evidence for deletion of 9q as a two-step process in chronic myeloid leukemia. Chronic myeloid leukemia (CML) is characterized by the Philadelphia translocation t(9;22)(q34;q11) resulting in the BCR/ABL fusion gene. Submicroscopic deletion of the derivative chromosome 9 occurs in a subset of these patients and is associated with poor prognosis. In the current study, we present two unusual cases of CML selected from a series of 54 consecutive cases. A detailed study using classical cytogenetics and fluorescence in situ hybridization (FISH) analysis was done using dual color extra signal FISH and whole chromosome paint in order to elucidate the mechanism of 9q deletion. One case had two clones on interphase FISH, one with and one without chromosome 9q deletion. The other case had two clones on both cytogenetic and FISH analyses, one with and one without a marker chromosome carrying chromosome 9q sequences. In this latter case, the clone with deletion of the derivative chromosome 9 comprised 21.1% at diagnosis, increasing to 36.8% after 11 months, suggesting a growth advantage. We report here evidence that deletions on 9q in CML may occur through breakage and rearrangement of chromosomes resulting in derivative chromosomes and either a marker chromosome or fragment/episome, followed by loss of chromosome material from the cell.

Pseudodicentric (16;12)(q11;p11.2) in a type AB (mixed) thymoma.

Genetic alterations of thymomas are rarely described in the literature. In this study, a previously unreported instance of aberrant karyotypic change consisting of 45,XX,pseu dic(16;12) (q11;p11.2) [cp23]/87-90,idemx2[cp4] in a Masaoka Stage II mixed thymoma or type AB thymoma affecting a 56-year-old Chinese woman is detailed. Abnormalities involving 12p containing important tumor suppressor-like genes have been documented especially in hematological malignancies. Recently, recurrent losses involving 16q, a locus known to harbor several tumor suppressor genes, have been described in type C thymomas (squamous cell carcinoma), suggesting a possible relationship between type AB thymoma and type C thymoma. Whether these genes are involved in the pathogenesis of type AB thymoma remain to be clarified and it is currently unclear if cytogenetic studies may eventually play a role in the classification of thymic tumors.