Unusual immunofluorescence patterns for terminal deoxynucleotidyl transferase in blast crisis chronic myelogenous leukemia.

An unusual cytoplasmic distribution of terminal deoxynucleotidyl transferase (TdT) antigen in leukemic cells from two patients who had chronic myelogenous leukemia in blastic phase is described. In most leukemic cells that contain TdT, the intracellular location has been reported to be exclusively nuclear. The cells from these two patients demonstrated TdT staining in both the nucleus and the cytoplasm. The pattern is remarkably similar to that observed in thymocytes, in which bright cytoplasmic staining may also be seen. In the immunofluorescence procedures for detection of TdT in blasts from patients who have chronic myelogenous leukemia, significant cytoplasmic staining should not be mistaken for nonspecific absorption of immunoglobulins or specimen deterioration.