False Positive Conventional Cytogenetic Findings that Mimic the Recurrent Chromosome Abnormalities Associated with Hematolymphoid Disorders

Recurrent chromosome abnormalities as defined in the World Health Organization (WHO) play a major role in diagnosis, prognosis, and treatment. Herein, we describe two cases of hematologic malignancies with chromosomal abnormalities mimicking WHO-define recurrent abnormalities. Both cases demonstrate clinical utility of interphase and metaphase fluorescence in-situ hybridization (FISH) in confirming the WHO defined recurrent cytogenetic abnormalities. The first is a case of chronic myeloid leukemia (CML) with both t(9;22)(q34;q11.2) and inv(3)(q21q26.2) by conventional cytogenetics but no EVI1::MECOM rearrangement by FISH. The second is a case of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) with deletion of 11q (ATM) and a subclone with deletion of 6q (MYB) and t(9;22)(q34;q11.2) detected by conventional cytogenetics but no BCR::ABL1 fusion by FISH. These cases demonstrate that conventional cytogenetics and FISH studies are complementary and especially so when recurrent abnormalities are suggested by karyotype.