Adult T cell leukemia with atypical surface phenotypes: clinical correlation

The leukemic cells of 57 patients with adult T cell leukemia (ATL) were analyzed for their immunologic surface markers. Forty-four cases showed normal mature inducer/helper T cell phenotype (typical group: E-RFC+, Leu-1+, 2a-, 3a+ MASO36c-), but the other 13 cases showed unusual surface phenotypes (variant group) and could be subdivided into several groups (V1 to V5). Four cases had absent or low Leu-1 positivity (V1: E-RFC+, Leu-1-, 2a-, 3a+, MASO36c-), while two other cases with low Leu-1 positivity had both Leu-2a and 3a, a characteristic of cortical thymocytes, but were unreactive with MASO36c (V2: E-RFC+, Leu-1-, 2a+, 3a+, MASO36c-). Three cases lacked both Leu-2a and 3a despite having other T cell markers (V3: E-RFC+, Leu-1+, 2a-, 3a-, MASO36c-). The next three cases had low rosette-forming ability with sheep RBCs (V4: E-RFC-, Leu-1- approximately +, 2a- approximately +, 3a+, MASO36c-). Interestingly, one other case showed high reactivity against anti-Leu-7, which is believed to be one of the monoclonal antibodies directed against natural killer cells (V5: E-RFC+, Leu-1+, 2a-, 3a+, 7+, MASO36c-). Clinical and hematologic differences between the typical group and variant group were investigated, and it was found that the variant group (excluding V5) have statistically significant (P less than .002) higher serum lactic dehydrogenase (LDH) activity. The overall survival in the variant group was worse than in the typical group, but it was not quite statistically significant (P = .072). The median survival time was eight months for typical cases and only four months for variant cases; six cases died within two months. The V5 case was unusual not only because the patient's leukemic cells have Leu-7 antigen but also because she survived more than nine years after initial diagnosis. There seems to be some correlation between phenotypic diversity of ATL cells and prognosis.