Dual surface makers and HTLV‐I proviral DNA in a cutaneous tumour nodule in a case of adult T cell leukaemia/lymphoma

SUMMARY The phenotypic and morphological profiles of atypical cells in a case of adult T cell leukaemia/ lymphoma were studied using a panel of monoclonal antibodies and electron microscopy. Retroviral sequence restriction analysis showed the presence of human T cell leukaemia/ lymphoma virus type I (HTLV-I) in the skin lesion. Our case showed several unique features in the clinical, haematological, histopathological and immunohistochemical findings. An erythematous plaque and tumour nodules in the skin were found without any abnormal lymphocytes such as flower cells in the peripheral blood and bone marrow HTLV-I provirat DNA was detected in the skin tumour cells but not in the peripheral blood lymphocytes, and in the tumour nodule, atypical cells showed a distinct difference in morphology between cerebriform cells in the upper dermis and large lymphoid cells in the lower dermis. The cerebriform cells had, immunohistochemically, a T helper/inducer (Th/i) phenotype whereas the large lymphoblastoid cells possessed both the Th/i and T suppressor/cytotoxic (Ts/c) phenotypes. Ki-i antigen was detected in the large tymphoblastoid cells, but not in the cerebriform cells.