"Pure" monocytic or histiomonocytic leukemia: a revised concept.

In a series of 130 cases of acute leukemia studied by cytochemical staining techniques, 10 cases cytochemically diagnosed as "pure" monocytic leukemia were seen. Cytochemical staining of bone marrow aspirates from these patients revealed all leukemic cells to be Sudan black negative. No positive reactions were observed for peroxidase or naphthol AS-D chloroacetate esterase. All cases demonstrated strong alpha-naphthyl acetate esterase positivity; and fluoride-inhibited naphthol AS-D acetate esterase positivity was observed in 8 of 9 cases tested. The P.A.S. reaction showed diffuse fine to coarse granules. Oil red O stain was positive in 8 of 9 cases, and the beta-glucuronidase activity was strong in 5 of 9 cases. Light microscopy revealed cells with monocytic or histiocytic morphology. Electron microscopic studies in 2 cases demonstrated features consistent with leukemic monocytic or histiocytic morphology; none was suggestive of granulocytic or lymphocytic leukemia. Five of 6 patients treated with drug regimens including prednisone and vincristine entered a complete remission; the other obtained a partial remission. Two patients achieved complete remission after treatment with Adriamycin, 1 following a relapse. Three patients who received cytosine arabinoside as their only therapy died soon after treatment was commenced. It is suggested that the cytochemical similarity but morphological differences in those patients may be objectively used to group them as cases of histiomonocytic leukemia.