Assessment of clonal relationships in malignant lymphomas

DNA sequencing of the antigen receptor genes remains the gold standard for the establishment of clonal relationships between samples. However, a variety of strategies may be employed as surrogates for the determination of the actual sequence of the clonally rearranged antigen receptor genes. The methods described in this chapter provide a framework for the rapid determination of clonal relationships between (microdissected) lymphoid populations. All of the methods described are PCR-based because of its versatility and ability to utilize very small amounts of DNA. For illustration purposes, the descriptions have been confined to B-cell populations. Although not described here, Ig kappa or Ig lambda PCR may also be utilized for determination of B-cell clonality and clonal relationships in the same manner. Similarly, the principles utilized may be extended to T-cell populations and T-cell receptor chain genes. Regardless of the methodology or targets involved, it is strongly recommended that all assays on microdissected material be run on parallel replicates of each sample to ensure reproducibility of results. The information about clonal relationships obtained by LCM has more than an academic significance and has utility in routine diagnostics for the establishment of minimal residual disease and the determination of microscopic disease recurrence vs the development of a secondary malignancy.