Chromosome studies in adult T-cell leukemia in Japan: Significance of trisomy 7

Chromosomes were studied in cells from 15 Japanese patients with adult T-cell leukemia (ATL). Mitoses were obtained from unstimulated peripheral blood in 12 patients and a lymph node in one patient. In two other patients, mitotic cells were obtained solely from peripheral blood stimulated with phytohemagglutinin (PHA). Chromosomally abnormal cells were seen in 14 of the 15 patients. The abnormal cells had a modal number of chromosomes in near diploid range in 12 patients, and in near triploid and tetraploid range in the remaining 2 patients, respectively. Eight of the nine patients analyzed by Q-banding had clonal chromosome abnormalities, The most common abnormality was trisomy no. 7 or 7q, which was seen in 5 cases and has been primarily observed in lymphoid neoplasms. A 14q+ marker chromosome was found in two patients and Dq+ in one patient; loss of a sex chromosome was found in three patients. Most chromosomes were involved in gains, losses, or structural rearrangements, but abnormalities of no. 11 which have been frequently found in lymphoid malignancies, was not observed in our series. The significance of these chromosome abnormalities is discussed.