Extra Y chromosome in chronic lymphoproliferative disorders.

Using separated lymphocytes from 95 male patients with B-cell lymphoproliferative disorders, we have established both Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines and short-term cultures with polyclonal B-cell mitogens. Cytogenetic studies of these patients revealed an extra Y chromosome in 4 of 71 male cell lines examined. An extra Y chromosome appeared to be the sole karyotype change (47,XY, + Y) in 2 of these 4 patients. The extra Y chromosome was accompanied by extra copies of chromosomes 12 and 21 (48,XY, + Y, + 12 and 48,XY, + Y, + 21) in the other 2 patients, respectively. The possible oncological role of the extra Y chromosome in the initiation of leukemia is discussed.