TRISOMY-12 IN RICHTERS TRANSFORMATION OF CHRONIC LYMPHOCYTIC-LEUKEMIA

Conventional cytogenetic data and fluorescence in situ hybridization ( FISH) interphase cytogenetic studies have shown that trisomy 12 is fou nd in many cases of B-cell chronic lymphocytic leukemia (B-CLL). Sever al reports indicate that +12 is an acquired numerical cytogenetic abno rmality, and may be associated with a worse prognosis or more extensiv e disease. Wright-Giemsa-stained blood or bone marrow smears obtained after initial diagnosis, and subsequent lymph node cells, bone marrow aspirate smears, or effusions were retrospectively studied from five p atients whose disease underwent morphologic transformation from typica l B-CLL to a high grade lymphoproliferative disease (Richter's syndrom e). Using an alpha-satellite DNA probe to the centromere of chromosome 12, trisomy 12 was found in a proportion of cells from all five speci mens with high grade lymphoproliferative disease, but in only one of f ive samples collected before transformation. These data suggest that 12 is an acquired cytogenetic abnormality in CLL and has a high freque ncy in Richter's syndrome. Because only a subpopulation of the neoplas tic cells contain an extra copy of chromosome 12, it is unlikely that this numerical abnormality plays a direct role in transformation to hi gh grade lymphoproliferative disease.