T-STEM CELL LEUKEMIA LYMPHOMA WITH BOTH MYELOID LINEAGE CONVERSION AND T-SPECIFIC DELTA-RECOMBINATION/

We evaluated retrospectively the clinical and biological characteristi cs of six patients with CD7(+) early T-acute lymphoblastic leukemia an d lymphoma (T-ALL/LBL) originating from prothymocyte stage I (pro-T I) or II cells. Patients exhibited mediastinal mass (five of six) and ly mphoadenopathy (five of six) but without leukocytosis and circulating blast cells (six of six). All patients achieved a complete remission. AII but one had a relapse with a transformation to the mixed type (tri phenotype-three cases, biphenotype-two cases) including myeloid featur es in three patients. The altered phenotypes were myeloperoxidase (MPO )(+) (three of five), CD13(+) (four of five), CD33(+) (three of five) and CD19(+) (three of five). The difference for MPO-positivity were ob served between the bone marrow (BM)- and lymph node (LN)-blast cells ( three of three). On cytogenetic analysis, there is no common abnormali ty in these patients. Immunomolecular analysis revealed T-cell lineage specific delta gene rearrangements [D delta 2-J delta 1 (five of six) and V delta 1-J delta 1 (one of six)] in all cases. Furthermore, D de lta 2-J delta 1 occurred even in the cases with the pro-T I phenotype. Rearrangements of TCR beta, gamma or immunoglobulin heavy chain genes occurred in three patients. The same rearranged band(s) appeared at b oth diagnosis and relapse, indicating the same originality of the pro- T leukemic cell clone (three of three). We suggest that this type of C D7(+) early T-ALL/LBL was transformed from a pro-T I or II cell, such as T-stem cell leukemia/lymphoma, which is a subtype of CD7(+) stem ce ll leukemia as defined by Kurtzberg at al. This study reveals that pro -T I and II cells might be capable of myeloid, T-and B-lymphoid differ entiation, and T-cell lineage specific TCR delta recombination occurs. (C) 1997 Elsevier Science Ltd.