The malignant lymphomas of Kenya: morphology, immunophenotype, and frequency of Epstein-Barr virus in 73 cases

Recent information is limited regarding pathological features of the malignant lymphomas of Africa, other than Burkitt's lymphoma. In this study, we apply modern techniques and nomenclature to classify 73 lymphomas from a central histopathology laboratory serving 40 mission hospitals in Kenya. We were particularly interested in the frequency of recently recognized lymphomas and the incidence of Epstein-Barr virus in various lymphoma subtypes. Malignant lymphomas accounted for 12% of all surgical pathology specimens processed in the laboratory over the 21-month period included in the study. Patient age ranged from 4 to 97 years (median, 35 years). The male-to-female ratio was 2.5:1. Sixty lymphomas (82%) were non-Hodgkin's, and 13 (18%) were Hodgkin's disease. Of the non-Hodgkin's lymphomas (NHLs), 52 (87%) were B-lineage, including 21 (35% of NHLs) Burkitt's lymphomas (only one from the jaw), 11 (18%) diffuse large B cell lymphomas; nine (15%) small lymphocytic lymphomas, six (10%) Burkitt's-like lymphomas, two (3%) follicular lymphomas (two of two expressed bcl-2 protein; one of two showed bcl-2 major breakpoint region rearrangement), two (3%) mantle cell lymphomas, and one extranodal marginal zone lymphoma. Of the eight T cell lymphomas, six were precursor T-cell type, and the remaining two were peripheral T cell lymphomas, unspecified. The median age of the 13 patients (18% of lymphomas) with Hodgkin's disease was 23 years (range, 9 to 97 years). Six were nodular sclerosis, four were mixed cellularity, one case each was lymphocyte depletion, lymphocyte predominance, and unclassified Hodgkin's disease. Hodgkin's cells in 6 of the 12 nonlymphocyte predominance cases were positive for CD20, and in three of the six for CD45 as well. Epstein-Barr virus was identified using in situ hybridization for EBER 1 in the malignant cells of 22 of 39 informative lymphomas, including each of 17 Burkitt's lymphomas, and three of seven diffuse large B cell lymphomas. Of note, none of five Burkitt's-like lymphomas expressed EBER 1. One of two informative cases of peripheral T cell lymphoma, and four of nine cases of Hodgkin's disease were EBER 1 positive. In summary, T cell lymphomas and recently recognized B-lineage non-Hodgkin's lymphoma subtypes do not appear to be particularly common in East Africa.