Chromosome 6 abnormalities associated with prolymphocytic acceleration in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is most characteristically associated with the cytogenetic abnormalities +12, 13q14, and 14q32. Recently abnormalities of chromosome 6 have been reported in patients with mantle zone lymphoma, CLL mixed type, and a CLL variant with larger prolymphocytoid cells in the peripheral blood. The purpose of this study was to review the cases of CLL karyotyped at the University of Texas M. D. Anderson Cancer Center (UTMDACC) and to determine the number and type of chromosome 6 abnormalities. Precisely 830 cases of CLL with karyotypes were reviewed. Among these, 257/830 (31 percent) had abnormal karyotypes, 56/257 (22 percent) had an abnormality of 6, 18/56 (32 percent) had translocations involving 6 and, in most instances, a different chromosome was involved, 37/56 (66 percent) had deletion 6 or loss of at least a portion of 6q, and 9/56 (16 percent) had an abnormality of 6p. The losses of 6q were in the q13 to q25 regions. Of these, 13/56 (23.2 percent) of patients with 6q abnormalities had ≤10 percent prolymphocytes (PL) in the bone marrow (BM) and/or peripheral blood (PB), 10/56 (17.9 percent) had ≤10 percent PL in the bone marrow, 8/56 (14.3 percent) had ≤10 percent PL in the peripheral blood, and 5/56 (9 percent) had ≤10 percent PL in both (see table I). The 201 CLL patients with chromosome abnormalities other than 6 contained 23 with excess PL (11.9 percent). A subset of karyotypic changes of 6 associated with increased PL is recognizable and may be useful in aiding in clinical diagnosis and therapy.