Aim: To compare the sensitivity of the detection of immunoglobulin light chain messenger RNA (mRNA) restriction by in situ hybridisation (ISH) and clonal immunoglobulin heavy chain gene rearrangements by polymerase chain reaction (PCR) in the diagnosis of B cell lymphoma.
Methods: Analyses were applied to formalin fixed, paraffin wax embedded, routine diagnostic specimens from cases with a provisional diagnosis of reactive lymph node (n = 23), B cell lymphoma (n = 21), and T cell lymphoma (n = 4). Nonisotopic ISH for kappa and lambda immunoglobulin light chain mRNA was performed using both fluorescein and digoxigenin labelled oligodeoxynucleotide probe cocktails. PCR was carried out on DNA extracted from sections using primers to framework 3 (Fr3) of the V segments and to conserved sequences from the J regions of the immunoglobulin heavy chain genes.
Results: All reactive lymph nodes showed a polyclonal pattern of light chain mRNA by ISH, although one showed an excess of kappa positive cells. Nineteen of 21 (90%) cases of B cell lymphoma showed light chain restriction, and a further case showed a vast excess of kappa positive cells. By PCR, 20 of 23 reactive nodes (87%) showed a polyclonal pattern. In 13 of 21 B cell lymphomas (62%) a clonal band was detected.
Conclusion: In the diagnosis of B cell lymphoma in routinely processed diagnostic material ISH for light chain mRNA was more sensitive (90%) than PCR for heavy chain gene rearrangement using Fr3 and J region primers (62%).