Molecular insight into the diagnosis of lymphoma

Malignant lymphoma may be very difficult to diagnose with routine histopathological methods because they may recapitulate benign architecture or contain benign infiltrates. The best method of diagnosis is to establish the clonal profile of the lymphocyte population, since a monoclonal proliferation is highly suggestive of neoplasia. By means of a PCR (polymerase chain reaction) method it is possible to detect the immunoglobulin heavy chain (IgH) gene rearrangement and therefore establish the lymphocyte clonality. PCR with primers complementary to relatively conserved regions called frameworks (FR1-FR3) laying among hyper variable regions (CDR1-CDR3) of IgH gene unable us to detect monoclonal versus polyclonal B-cell population. The length of the PCR product with these primers is unique if we deal with a monoclonal population. On the contrary, a polyclonal population gives PCR products of a different size. In this retrospective study we used a semi-nested PCR to analyse 37 paraffin-embedded specimens. All of them had been evaluated previously by pathohistological and immunophenotypic criteria. A number of polyclonal (PBL and tonsils from healthy donors) and monoclonal cells (PBL from CLL patients, Raji cell line) were analyzed as controls. Clonality was successfully determined in all specimens. Our results support the concept that molecular techniques such as PCR provide a helpful approach for detection of monoclonal immunoglobulin rearrangements in malignant lymphoma. This is especially true for border cases, but always in the combination with other pathohistological methods.