Acute myelomonocytic leukemia in children. Possible use of the soft agar culture technique in the differentiation of cellular subtypes.

In 8 children with acute myelomonocytic leukemia (AMML), colony formation in soft agar cultures derived from bone marrow cells was studied in an attempt to differentiate the monocytic (Schilling) from the myelomonocytic (Naegeli) types. The children did not differ markedly in their clinical and morphological parameters. Three in vitro growth patterns were observed: markedly decreased or no growth in 4 cases, extensive growth of granulocytic colonies in 2 cases, and extensive growth of macrophage colonies in the remaining 2. It is suggested that the marrows presenting diminished or no growth patterns are presumably of acute myelogenous leukemia patients with a monocytic component. The excessive granulocytic or macrophage colony growth may be an in vitro indication for an in vivo proliferation of either granulocytic or monocytic leukemic cell lines, and therefore may represent the Naegeli or Schilling variants of AMML respectively. If these observations can be approved in a larger series of AMML patients, this approach can be valuable as another tool in the differential diagnosis of the subtypes of AMML in children.