Comparison of outcome, clinical, laboratory, and immunological features in 164 children and adults with T-ALL. The Groupe d'Etude Immunologique des Leucémies.

T cell acute lymphoblastic leukemia (T-ALL) is a disease of poor prognosis, usually studied separately in adults or children. Controversial clinical or biological prognostic factors have been reported, and little information is available regarding the frequency and prognostic value of membrane markers identified on blast cells. We report an extensive investigation of the incidence and prognostic value of immunophenotypic, clinical, and laboratory data in T-ALL, performed as a multicenter study in 164 patients. CD7, CD5, and CD2 were the most frequently expressed T cell antigens, and CD2 and CD4 were more frequently observed in children than in adults. MHC class II, CD9, and CD10 were observed in 16, 22, and 21% of the patients, respectively. The male prevalence of T-ALL, and the more frequent presence of a tumoral syndrome in children were confirmed, but mediastinal enlargement and high leukocyte counts were observed in less than half the patients. A poor prognosis was associated with the expression of MHC class II in adults. The presence of a mediastinal mass appeared to be of good prognosis in adults, as well as a leukocyte count lower than 100 x 10(9)/l whatever the age of the patient.