Primary central nervous system lymphoma in Miyazaki, southwestern Japan, a human T-lymphotropic virus Type-1 (HTLV-1)-endemic area: clinicopathological review of 31 cases.

Primary central nervous system lymphoma (PCNSL) is a rare and aggressive brain tumor. The aim of this study was to clarify the prevalence of T-cell-type PCNSL (T-PCNSL) in a human T-lymphotropic virus type-1 (HTLV-1)-endemic area of Southwestern Japan. We retrospectively investigated 31 PCNSL cases diagnosed between 1996 and 2013 at the University of Miyazaki Hospital. These cases accounted for 4.4% of all nodal or extranodal malignant lymphomas. Histologically, most of these cases were diagnosed as diffuse large B-cell lymphoma, while only two cases were considered to be low-grade and high-grade B-cell lymphoma (not otherwise specified). No T-PCNSL was found in this series. In addition, Epstein-Barr virus-encoded RNAs were not detected by in situ hybridization in any of the cases. Overall, no T-PCNSL cases were found in 18 years in a region with a high frequency of HTLV-1 seropositivity, namely, Southwestern Japan. This suggests that PCNSL and lymphomas of other anatomical sites are biologically distinct.