Myelodysplastic syndrome (MDS) represents a heterogeneous group of hematologic malignancies characterized by ineffective hematopoiesis, resulting in cytopenias and a high risk of progression to acute myeloid leukemia (AML). Approximately 50% of patients with MDS have chromosomal abnormalities, which are a prognostic marker. The most common chromosomal abnormalities in MDS include deletion of the long arm of chromosome 5 [del(5q)], alterations in chromosome 7 (deletion of the long arm of chromosome 7 [del(7q)]/monosomy 7), and trisomy 8. Alterations in chromosome 7 are associated with an unfavorable prognosis. The chromosomal abnormalities [-7/del(7q)] affect genes critical for cellular regulation, leading to dysfunctions in the development and maturation of blood cells. The unbalanced translocations der(7)t(1;7) has been considered by some studies as a variant of chromosome 7 alterations, presenting a prognosis similar to these alterations. However, according to the Revised International Prognostic Scoring System (IPSS-R), the der(7)t(1;7) presents an intermediate prognosis.

To report cases of patients with MDS who presented the unbalanced translocations der(7)t(1;7) and their clinical outcomes.

This study included 4 patients of a total of 460 adult patients with MDS, between 2000-2023. Cytogenetic analyses were performed on bone marrow cells by G-banding and fluorescence in situ hybridization (FISH).

Chromosomal abnormalities were observed in 41% (190/460) of the patients. Of these patients, four had unbalanced translocations involving chromosomes 1 and 7. The patients were classified in advanced subtypes (MDS-AB1/AB2) and progressed to AML. Of these patients, three had der(7)t(1;7)(q10;q10) and one patient had a different breakpoint region [46,XY,der(7)t(1;7)(q21;q31)]. Not previously reported in the literature.

Although uncommon, unbalanced translocation involving the der(7)t(1;7)(q10;q10) breakpoints has been previously reported in approximately 0.6% to 2.6% of MDS cases. Some studies suggest that der(7)t(q10;p10) is associated with a more favorable prognosis compared with -7/del(7q), while others have not observed significant differences in prognosis between these cytogenetic alterations. In our study, we observed that these chromosomal translocations were associated with advanced disease subtypes and progression to AML.

Our study suggests that der(7)t(1;7) is associated with an unfavorable clinical outcome in adult patients with MDS.

Ministério da Saúde – INCA.