Isolated isochromosomes i(X)(p10) and idic(X)(q13) are associated with myeloid malignancies and dysplastic features

Cytogenetics in the management of myelodysplastic neoplasms (myelodysplastic syndromes, MDS): Guidelines from the groupe francophone de cytogénétique hématologique (GFCH)

Myelodysplastic neoplasms (MDS) are clonal hematopoietic neoplasms. Chromosomal abnormalities (CAs) are detected in 40-45% of de novo MDS and up to 80% of post-cytotoxic therapy MDS (MDS-pCT). Lately, several changes appeared in World Health Organization (WHO) classification and International Consensus Classification (ICC). The novel 'biallelic TP53 inactivation' (also called 'multi-hit TP53') MDS entity requires systematic investigation of TP53 locus (17p13.1). The ICC maintains CA allowing the diagnosis of MDS without dysplasia (del(5q), del(7q), -7 and complex karyotype). Deletion 5q is the only CA, still representing a low blast class of its own, if isolated or associated with one additional CA other than -7 or del(7q) and without multi-hit TP53. It represents one of the most frequent aberrations in adults' MDS, with chromosome 7 aberrations, and trisomy 8. Conversely, translocations are rarer in MDS. In children, del(5q) is very rare while -7 and del(7q) are predominant. Identification of a germline predisposition is key in childhood MDS. Aberrations of chromosomes 5, 7 and 17 are the most frequent in MDS-pCT, grouped in complex karyotypes. Despite the ever-increasing importance of molecular features, cytogenetics remains a major part of diagnosis and prognosis. In 2022, a molecular international prognostic score (IPSS-M) was proposed, combining the prognostic value of mutated genes to the previous scoring parameters (IPSS-R) including cytogenetics, still essential. A karyotype on bone marrow remains mandatory at diagnosis of MDS with complementary molecular analyses now required. Analyses with FISH or other technologies providing similar information can be necessary to complete and help in case of karyotype failure, for doubtful CA, for clonality assessment, and for detection of TP53 deletion to assess TP53 biallelic alterations.

Cytogenetics in the management of acute myeloid leukemia and histiocytic/dendritic cell neoplasms: Guidelines from the Groupe Francophone de Cytogénétique Hématologique (GFCH)

Genetic data are becoming increasingly essential in the management of hematological neoplasms as shown by two classifications published in 2022: the 5th edition of the World Health Organization Classification of Hematolymphoid Tumours and the International Consensus Classification of Myeloid Neoplasms and Acute Leukemias. Genetic data are particularly important for acute myeloid leukemias (AMLs) because their boundaries with myelodysplastic neoplasms seem to be gradually blurring. The first objective of this review is to present the latest updates on the most common cytogenetic abnormalities in AMLs while highlighting the pitfalls and difficulties that can be encountered in the event of cryptic or difficult-to-detect karyotype abnormalities. The second objective is to enhance the role of cytogenetics among all the new technologies available in 2023 for the diagnosis and management of AML.