Primary mediastinal large B-cell lymphoma: a single-center study of clinicopathologic characteristics.

Primary mediastinal large B-cell lymphoma (PMLBCL) is a subset of LBCL with unique clinicopathologic features. Some studies have raised the question of differences in biological features and clinical course among patients from different parts of the world. We conducted a retrospective clinicopathologic analysis of 24 patients with PMLBCL from a single center in Croatia. We also conducted the first investigation of the frequency of lymphotropic viruses human herpesvirus 6 (HHV-6) and HHV-8 in lymphoid lesions of this disease. The clinical characteristics of the patients were as expected, with high International Prognostic Index scores, elevated serum lactate dehydrogenase (LDH) levels, and bulky disease being adverse prognostic factors. Only 6 patients (25%) showed CD30 expression, and Bcl-6 protein expression was, in our series, prognostically favorable (P = .0401). One patient's tumor had detectable HHV-6 genome sequence, but no HHV-8 sequences were detected in any tumors. Two thirds of the patients received CHOP chemotherapy (cyclophosphamide, hydroxydaunomycin, vincristine, and prednisone) with a relatively low complete remission rate (43.8%; median follow-up, 33.8 months). This study confirmed the moderate preponderance among PMLBCL patients of young females with B symptoms and elevated LDH levels. The CHOP regimen proved effective as first-line therapy only in patients with limited disease. Therefore, other third-generation chemotherapy protocols may be considered for treatment, especially in patients with bulky and advanced disease.