Increased levels of myeloid progenitor cells in the blood of patients with metastatic invasion of the marrow.

Granulocyte-macrophage clusters and colony-forming cells (CFU-C) in the peripheral blood have been studied in 26 cancer patients with neoplastic bone marrow involvement. The concentration of CFU-C in the blood of normal individuals and of cancer patients with no bone marrow invasion, ranged from 0 to 99 ml. In contrast, out of 27 cancer patients with marrow invasion, 9 (35%) showed a significant increase of blood CFU-C (100 to 21000/ml) and of those 5 (19%) showed an increase of blood colonies (41 to 9000/ml). There was a strong correlation between increased CFU-C or colony concentration and the presence of myeloid or/and erythroid immature cells in the peripheral blood. On the other hand, there was no apparent correlation between an increased CFU-C level and anaemia or abnormal blood leucocyte count or marrow fibrosis. These observations suggest that bone marrow involvement by neoplastic cells may cause spatial redistribution of the granulocyte macrophage progenitor cells.