Cytogenetic findings in untreated patients with essential thrombocythemia.

Essential thrombocythemia (ET) is a chronic myeloid disorder that is characterized by persistent thrombocytosis, thrombohemorrhagic symptoms and a low risk of transformation to leukemia. Chromosomal abnormalities in ET are very rare and most of the patients studied were either in leukemic transformation or they had received treatment with cytotoxic agents. The number of cases studied at the time of diagnosis is very limited. In the present study, 67 cases with ET, at the time of diagnosis, were cytogenetically studied by a G-banding technique. Among them, only four presented chromosomal abnormalities. In two cases, a del(5)(q13q33) was identified, accompanied by trisomy 20 in one case, while, in the other case, monosomy 17 and a small marker chromosome were additionally found. In each of the remaining two abnormal cases, clonal isolated trisomy 13 or monosomy 14 were found, respectively. Since these chromosomal abnormalities were found at the time of diagnosis, they might be related to the neoplastic process. The documentation of more cases of chromosomal abnormalities in ET at the time of diagnosis may facilitate the identification of candidate genes involved in the neoplastic process.