Splenic lymphoproliferative disorders in human T lymphotropic virus type-I endemic area of japan: clinicopathological, immunohistochemical and genetic analysis of 27 cases

Primary splenic involvement in lymphoid neoplasms is rare and the clinicopathologic features of splenic lymphoma are not well described compared to nodal non-Hodgkin's lymphoma (NHL). Here we characterized splenic lymphomas in an human T lymphotropic virus type-I (HTLV-I) endemic area of Japan. To assess the pattern of splenic involvement and evaluate prognosis, we reviewed 27 specimens consisting of 26 splenectomies and one necropsy, which were classified using REAL classification. Cases were divided into primary splenic lymphoma in 11 patients and secondary in 16 patients. The incidence of primary splenic lymphoma was 0.3% (11 of approximately 4,000 malignant lymphomas). Primary splenic lymphomas included 7 diffuse large B cell lymphoma (DLBL), 2 follicular lymphomas (FL), and 1 each of splenic marginal zone lymphoma (SMZL) and anaplastic large cell lymphoma (ALCL). Secondary splenic lymphomas included 6 DLBL, 4 mantle cell lymphoma (MCL), 2 FL, 2 Hodgkin's disease (HD), 1 each of hairy cell leukemia and ALCL. Gross examination showed two patterns of splenic involvement; solid type (formation of large nodular mass, n=16) and disseminated type (multiple nodules with diffuse infiltration but no large nodular formation, n=10). The type could not be determined in one case. Most solid types were DLBL or FL, while MCL was of the disseminated type. Immunohistochemistry showed all but each 2 cases of ALCL and 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 malignant 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 Epstein-Barr virus (EBV) showed no reactivity of lymphoma cells, although a few small lymphocytes were positive for EBV. Hepatitis C virus was observed in 6 of 20 (30%) patients examined and 4 of 11 (36%) cases of primary splenic lymphoma. Our findings indicate that patients with primary splenic lymphoma have a favorable prognosis after splenectomy.