Chronic monocytic leukemia in adults.

Clinical, hematologic, and histologic material from five patients with chronic monocytic leukemia is analyzed, and the literature is reviewed on 28 patients either reported as having this disease or referenced as such in subsequent publications. Patients with chronic monocytic leukemia have a characteristic clinical course. All have splenomegaly of uncertain etiology, and initial hematologic evaluation usually shows anemia with normal leukocyte and differential counts. One of the authors' patients had slight monocytosis at presentation. In the four patients for whom presplenectomy bone marrow smears were available for review, there was no detectable increase in the number of monocytes. The patients developed monocytosis, usually with accompanying leukocytosis, at intervals ranging from 3.5 to 24 months after splenectomy. In all patients, there was a corresponding increase in the numbers of mature monocytes in the bone marrow. Survival times from the detection of monocytosis ranged from five to eight months. Of the 28 cases reported in the literature, only two were considered by the authors of this study to have the characteristics of chronic monocytic leukemia, and of these, only one had features identical to those reported in the present series. The remainder represent a variety of hematologic disorders including chronic myelomonocytic leukemia, acute leukemia, histiomonocytic proliferations that cannot be sub-classified, and cases in which the data are insufficient for analysis. The differential diagnosis includes chronic myelomonocytic leukemia, chronic malignant histiocytosis, and hairy cell leukemia. In chronic monocytic leukemia, in contrast to hairy cell leukemia, splenectomy does not appear to be beneficial. Although chronic monocytic leukemia is an extremely rare disease, it is a distinct hematologic entity that appears to have a characteristic clinical course.