Incidence and pathology of primary brain lymphoma in Hong Kong Chinese patients

Primary brain lymphoma (PBL) is an uncommon extranodal lymphoma. Its incidence is rapidly increasing in both immunocompromised and immunocompetent patients in Western countries. Eighteen cases of PBL were identified during a 16-year period among HIV negative patients in Queen Mary Hospital, Hong Kong. One case of post-transplantation lymphoproliferative disease (PTLD) was positive for Epstein Parr virus (EBV) encoded RNA (EBER) by in situ hybridization. All the remaining 17 immunocompetent cases were classified as diffuse large B-cell lymphoma, except for one case of Burkitt's lymphoma. EBER expression was negative in all 13 cases tested. Immunostaining for bcl-2 and bcl-6 was positive in 8/11 and 6/11 cases tested, with heterogeneous combination of expression and intensity. The incidence rate of PBL in immunocompetent patients was stable at 1.03 per million per year. The incidence of PBL in post transplantation (0.16%) and HIV related setting (0.29%) is also low in Chinese. PBL in Chinese patients is almost uniformly represented by EBV negative, diffuse large B-cell lymphoma, confined to the brain. However, the molecular pathogenesis may be heterogeneous.