Analysis of immunoglobulin H gene rearrangement by polymerase chain reaction in primary central nervous system lymphoma

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Abstract
Diagnosing primary central nervous system lymphoma (PCNSL) may be difficult either because of a paucity of tumor cells in the brain biopsy specimens or a failure to demonstrate monoclonality on immunomorphological studies. Monoclonality can also be demonstrated by amplification of the rearranged immunoglobulin H genes by polymerase chain reaction (PCR) to the framework region (FR)3 and FR2 complementarity determining region (CDR)-III and CDR-II of these genes. The PCR method is feasible with formalin-fixed, paraffin-embedded biopsy material and has proven to be helpful in the diagnosis of non-Hodgkin lymphoma on biopsy samples obtained from various locations in the body. Nevertheless, few studies have addressed the value of this method in the context of PCNSL. In the present study, the contribution of both FR3 single and FR2 seminested PCR procedures for confirming the diagnosis of PCNSL was estimated retrospectively in 30 cases of PCNSL and in three cases of epidural lymphoma. Twenty-eight cases of immunophenotypically confirmed PCNSL and two of suspected lymphoma were studied. Tissue specimens obtained in 22 cases of other cerebral diseases, among which were various inflammatory conditions. were used as negative controls. In 18 (60%) of 30 cases the results of FR3 PCR demonstrated monoclonality, whereas FR2 PCR showed monoclonality in 12 cases (40%). In 11 cases FR3 PCR yielded monoclonal patterns and FR2 PCR did not, whereas reversibly in five cases FR2 PCR proved monoclonality and FR3 PCR failed to do so. Adding the results of FR3 to those of FR2 PCR, monoclonal patterns were obtained in 23 (77%) of 30 cases. In both cases in which lymphoma was suspected but not proven immunomorphologically, FR3 PCR revealed monoclonality, as did FR2 PCR in one case. In all 22 control lesions either polyclonal patterns were seen or no consistent patterns were obtained. In the PCNSL group, older age of patients and multifocal presentation of lesions on neuroimaging were significantly associated with worse survival. No correlation between histological subtype and clinical outcome was elucidated. The application of FR3 and FR2 PCR is a useful additional tool in making the diagnosis of PCNSL. Moreover, in some cases the PCR method may be essential in distinguishing neoplasia from reactive conditions.