Comparison of the expression of terminal deoxynucleotidyl transferase and common acute lymphoblastic leukemia antigen in selected hematologic malignancies.

Assays were performed on cells from 38 consecutive malignancies for both terminal deoxynucleotidyl transferase (TdT) and common acute lymphoblastic leukemia antigen (CALLA). TdT and CALLA occurred together only on lymphoblasts from some cases of acute lymphoblastic leukemia (ALL). In other cases of ALL, chronic myelogenous leukemia (CML) in blast crisis, and acute undifferentiated leukemia (AUL), TdT was expressed, but CALLA was absent. TdT was present predominantly on cells from the lymphoid lineage as proven by special histologic stains, and CALLA marked a population with a favorable prognosis. Significant discrepancies in the expression of these two markers and the unique properties of each suggest that both markers are useful for the full characterization of specific hematologic malignancies.