SURFACE-IMMUNOGLOBULIN LIGHT CHAIN-POSITIVE ACUTE LYMPHOBLASTIC-LEUKEMIA OF FAB L1 OR L2 TYPE - A REPORT OF 6 CASES IN ADULTS

Acute lymphoblastic leukemia (ALL) of B-cell lineage may be classified using the French-American- British (FAB) classification as L1, L2, or L3 type. L1 and L2 ALLs characteristically express terminal deoxynucl eotidyl transferase (TdT) and are surface immunoglobulin (sIg)-negativ e. In contrast, L3 ALL is typically TdT-negative and sIg-positive. How ever, in a few large studies of children with ALL, sIg expression has been reported in less than 2% of L1 and L2 neoplasms. In these sIg-pos itive cases, IgM usually has been detected with Ig light chain in a su bset of tumors. Surface Ig expression in L1 or L2 ALL in adults is ext remely rare; we found only I case report in the English literature. We report 6 cases of L1 or L2 ALL with an unusual immmnophenotype arisin g in adults. In each tumor, the neoplastic cells expressed monotypic s ig light chain (4 lambda, 2 kappa) and TdT. Three tumors expressed CD3 4. Cytogenetic studies in 4 cases at diagnosis or relapse revealed no evidence of chromosomal translocations involving the c-myc locus, such as the t(8;14), t(2;8), or t(8;22). Three patients responded complete ly to chemotherapy and are alive, follow-up ranges from 18 to 57 month s. Three patients died at 3, 13, and 14 months after diagnosis.