Splenic lymphoproliferative disorders in human T lymphotropic virus type-1endemic area of Japan: Clinicopathological, immunohistochemical and genetic analysis of 27 cases

Primary splenic involvement in lymphoid neoplasms is rare and the clinicopa thologic features of splenic lymphoma are not well described compared to no dal non-Hodgkin's lymphoma (NHL). Here we characterized splenic lymphomas i n an human T lymphotropic virus type-I (HTLV-I) endemic area of Japan. To a ssess the pattern of splenic involvement and evaluate prognosis, we reviewe d 27 specimens consisting of 26 splenectomies and one necropsy, which were classified using REAL classification. Cases were divided into primary splen ic lymphoma in 11 patients and secondary in 16 patients. The incidence of p rimary splenic lymphoma was 0.3% (11 of approximately 4,000 malignant lymph omas). Primary splenic lymphomas included 7 diffuse large B cell lymphoma ( DLBL), 2 follicular lymphomas (FL), and 1 each of splenic marginal zone lym phoma (SMZL) and anaplastic large cell lymphoma (ALCL). Secondary splenic l ymphomas included 6 DLBL, 4 mantle cell lymphoma (MCL), 2 FL, 2 Hodgkin's d isease (HD), 1 each of hairy cell leukemia and ALCL. Gross examination show ed two patterns of splenic involvement; solid type (formation of large nodu lar mass, n=16) and disseminated type (multiple nodules with diffuse infilt ration but no large nodular formation, n=10). The type could not be determi ned in one case. Most solid types were DLBL or FL, while MCL was of the dis seminated type. Immunohistochemistry showed all but each 2 cases of ALCL an d HD were of B lineage. Follow-up of 26 patients indicated that all but one patient with primary lymphoma were still alive (range, 1-89 months) and 8 of 15 patients with secondary lymphomas died due to the progression of mali gnant lymphoma; the survival. rate at 2 years was 50% in these patients. No elevation of anti-HTLV-I antibody was found. In situ hybridization for Eps tein-Barr virus (EBV) showed no reactivity of lymphoma cells, although a fe w small lymphocytes were positive for EBV. Hepatitis C virus was observed i n 6 of 20 (30%) patients examined and 4 of 11 (36%) cases of primary spleni c lymphoma. Our findings indicate that patients with primary splenic lympho ma have a favorable prognosis after splenectomy.