Identification of monocytic nature in acute undifferentiated leukemia by in vitro marrow culture study.

We report a case with acute undifferentiated leukemia whose leukemic blasts lacked morphological, cytochemical and immunological features of lymphoid or myeloid differentiation. The in vitro culture study defined her leukemia as of monocytic origin. Her marrow blasts underwent monocytic differentiation with strong nonspecific esterase activity when cultured in a liquid system with human placental conditioned medium. The semisolid agar culture showed an AML-type growth pattern. The present study indicates that in vitro culture study can be used as a supplement to improve the classification of certain unclassifiable leukemias.