Pathologic characteristics of human T-cell lymphotropic virus (HTLV)-related extranodal orofacial lymphomas. Eleven cases of extranodal orofacial lymphomas (EOFL), consisting of four HTLV-related and seven HTLV-unrelated EOFL, were investigated with respect to the immunohistochemical and clinical features. HTLV-related EOFL were of T-cell phenotype and were associated with a poorer prognosis than HTLV-unrelated EOFL, most of which were of B-cell origin. The appearance of giant cells with cerebriform nuclei was helpful in identifying HTLV-related EOFL. The relatively high incidence of T-cell type EOFL in our series was considered to be related to the high percentage of HTLV carriers in our district, an area endemic for adult T-cell leukemia-lymphoma. 