Significance of extra 18q- chromosome in Japanese t(14;18)-positive lymphoma

Abstract

Karyotype evolution of t(14;18)-positive lymphoma was studied in 13 Japanese patients. The extra 18q- chromosome, found in six of ten patients with complex karyotypes, was the most common change subsequent to a t(14;18)(q32;q21) chromosome translocation. The additional change was interpreted as being a duplication of an 18q- derived from a t(14;18). The six patients had transformed histology of follicular small cleaved cell lymphoma or diffuse large cell lymphoma, and five of them had extranodal expansion associated with a poor prognosis. These findings indicate that the extra 18q-, together with other chromosome abnormalities, is closely associated with the advanced grade disease of t(14;18)-positive lymphoma, and the extra chromosome is evolutionally comparable with the second Philadelphia (Ph1) chromosome often found in the blastic phase of chronic myelocytic leukemia carrying a t(9;22)(q34;q11). In addition, since the extra 18q- is rarely found in American patients with t(14;18)-positive lymphoma, there appears to be a difference in the karyotype evolution between Japanese and American patients.

Sequential karyotypes in non‐Hodgkin lymphoma: Their nature and significance

“…Examining nonsequential karyotypes, several investigators have inferred that karyotypic changes occurring in the presence of more frequently identified abnormalities in N H L are evolutionary in nature. In these studies, usually conducted in patients with follicular lymphomas, the "evolutionary" cytogenetic abnormalities frequently involve chromosomes 6, 7, and 18, although a number of other chromosomes and regions have also been implicated (Richardson eta]., 1987;Yunis et al, 1987;Armitage et al, 1988;Fukuhara et al, 1988). Only one other study has specifically addressed karyotypic changes among sequential biopsies in N H L ; like our own series, additional structural abnormalities of chromosome 1 were commonly identified, but no specific band or region of chromosome 1 was repeatedly affected (Sanger et al, 1987).…”