Ultrastructural study of acute lymphocytic leukemia: comparison with immunologic studies.

Leukemic cells from 29 cases of acute lymphocytic leukemia (ALL), studied for T and B cell markers by the use of sheep erythrocyte rosetting and surface immunoglobulin determinations, were examined by electron microscopy. The majority of patients (76%) were found to have non-T, non-B neoplasms composed predominantly of relatively small, inactive-appearing cells with frequent nuclear folds. T cell cases (21%) were associated with mediastinal masses and were predominantly composed of large, active-appearing cells with nuclear irregularity and little rough endoplasmic reticulum. One case of B cell origin was not morphologically distinct from the non-T, non-B cell cases.