Histological and immunoglobulin VH gene analysis of interfollicular small lymphocytic lymphoma provides evidence for two types

Interfollicular small lymphocytic lymphoma (I-SLL) has not been well charac terized and its relationship to small lymphocytic lymphoma (SLL) or chronic lymphocytic leukemia (CLL) is uncertain. Moreover, two different prolifera tion center growth patterns have been described with respect to reactive ge rminal centers. in this study, we evaluate the histological and immunopheno typic features of 13 cases of I-SLL. and immunoglobulin heavy chain variabl e (VH) gene sequences from 10 cases, Immunophenotypic analyses indicate tha t cases showing either growth pattern have the same CDS-positive B cell phe notype typical of SLL or CLL, Sequence analysis revealed the use of VH, D, and J gene segments often found in CLL, though there may be more frequent u se of J6, Similar to recent studies of CLL, there were approximately equal numbers of cases with either mutated or unmutated VH genes without evidence of ongoing mutation, consistent with I-SLL having either a naive or memory B cell origin. interestingly, the mutational status of the I-SLL VH genes seemed to correlate with the two different histological growth patterns. Th ese studies support the proposal that I-SLL, represents SLL/CLL and suggest the recently proposed two types of CLI, originating from either memory or naive B cells may have different histological patterns of growth in lymph n odes that show architectural preservation.