Purpose: To search for subclinical systemic disease in bone marrow and peripheral blood in patients with primary CNS lymphoma (PCNSL) to elucidate whether extracerebral relapse may represent a sequel of initial occult systemic disease rather than true extracerebral spread.
Patients and methods: Bone marrow and peripheral-blood specimens of 24 PCNSL patients were examined using polymerase chain reaction (PCR) for analysis of clonally rearranged immunoglobulin heavy-chain (IgH) genes.
Results: Identical dominant PCR products were found in bone marrow aspirates, blood samples, and tumor biopsy specimens of two patients, indicating that the same tumor cell population is present in the CNS and in extracerebral sites. Follow-up IgH PCR performed in one of these patients in complete remission 24 months after diagnosis yielded a persistent monoclonal product in the blood. An oligoclonal IgH rearrangement pattern was found in the tumor specimen of two other patients, whereas bone marrow and blood samples demonstrated the same dominant PCR products. Follow-up PCR showed a persistent monoclonal amplificate in blood in one of these patients 27 months after diagnosis.
Conclusion: It could be demonstrated for the first time that subclinical systemic disease can be present in PCNSL patients at initial diagnosis. Our findings may have an impact on the understanding of PCNSL pathogenesis and the extent of staging and treatment.