Chromosomal Aberrations in Brazilian Patients with Hematopoietic and Lymphoid Disorders - Consecutive Analysis of 1.052 Karyotypes

To date, clonal chromosome aberrations have been found in tumors from more than 61,000 patients (http://cgap.nci.nih.gov/Chromosomes/Mitelman). The molecular characterization of these recurrent abnormalities has provided insights into the mechanisms of oncogenesis, and in few cases helped in the use of target-therapy. Hematologists and cytogeneticists are encouraged to publish these abnormalities, mainly when they were not described or described in only a few cases in the literature.

To describe the most observed and the incidence of rare recurrent cytogenetic abnormalities in a routine cytogenetic laboratory and their association with diagnosis.

From December 2007 to May 2012, 5,173 karyotypes from 4,122 patients with known or suspected hematopoietic and lymphoid disorders were processed at the cytogenetic laboratory of Hospital Albert Einstein in São Paulo, Brazil. Of these, 1,052 (20.3%) showed abnormalities. Abnormalities were categorized as: isolated (a structural abnormality or a loss of an autosomal or sexual chromosome), 2 abnormalities, hyperdiploid (clone with 47 chromosomes or more without structural abnormalities) and structurally complex (3 or more abnormalities, including a structural). Rare recurrent abnormalities (described in less than 20 cases in the literature) and abnormalities not previously described are reported. The frequency of the abnormalities according to the diagnosis was also shown.

The mean age of the patients was 60 years old (30 days to 97 years); 58.1% were male. The distribution of the different entities was: ALL (10.3%), AML (21.1%), CLL (9.7%), CML (20.1%), multiple myeloma (2.8%), MPD (1.9%), MDS (13.3%), other malignancies (1.4%) and inconclusive (19.5%) cases.

The frequency of abnormal karyotypes with isolated, 2 abnormalities, hyperdiploid and structurally complex were respectively: 608 (57.8%), 115 (10.9%), 107 (10.2%) and 222 (21.1%). Complex karyotypes were more observed in ALL, MM and CLL, followed by MDS and AML and less frequently by MPD and CML (p <0.05).

The most frequent observed abnormalities were:-Y (10.5%), del(5q) (8.4%), del (6q) (12.1%), del(7q) (4.3%), +8 (7.4%), t(8;21) (2.3%), t(9;22) (21.2%), 11q23 rearrangement (3.4%), +12 (2.4%), t(15;17) (4.3%) and del(20q) (3.8%).

Thirty-four cases (3.2%) showed rare or not recurrent chromosome abnormalities, most of them as sole anomaly. From the 15 rare cases, we found 12 with reciprocal translocations, 2 with dicentric chromosomes and 1 with inversion; 10 of these cases occurred in myeloid and 5 in lymphoid disorders. Nineteen cases showed abnormalities not yet described: 2 characterized as constitutional (balanced translocations), 15 with reciprocal translocations (11q23 rearrangement, but not involving MLL gene) and 2 with inversion; 11 of these cases occurred in myeloid diseases.

The most frequent cytogenetic aberrations (Ph chromosome, 5/7 anomalies, trisomy 8 and –Y) shows the predominance of myeloid disorders and older population in this study. As expected, complex karyotypes were more prevalent in lymphoid diseases. The incidence of rare translocations is not low, and we need further efforts to characterize the genes involved in these rearrangements.

No relevant conflicts of interest to declare.