Follow-up study on bone marrow reticulin fibrosis in AML.

Planimetric analysis of argyrophilic (reticulin) fibers of the bone marrow was performed on 17 patients (7 males, 10 females, median age 52 years) with acute myeloid leukemia (AML). Trephine biopsies were investigated at presentation and during the course of chemotherapy. Density of reticulin was determined by examining the total marrow area as well as the hematopoietic tissue. In about half of the patients with FAB-subtypes M4, M5 an increased amount of fibers was recognizable on admission in comparison with age-matched controls. Two to five bone marrow biopsies (total 81) of each patient were obtained at intervals ranging mostly between three and seven weeks after cytotoxic treatment. The following results could be demonstrated: in several patients with a normal or elevated fiber count at onset, partial and complete remission was characterized by an increase in reticulin in the regenerative hematopoietic tissue. On the other hand, a relapse was most frequently heralded by a reduction of the formerly increased amount of fibers. Because of the inverse relationship between the density of argyrophilic fibers and the amount of fat cells, these findings were observable only by considering the hematopoietic tissue and not the total marrow area, as has been done in previous studies. For this reason a significant decrease in reticulin fibers in the areas of regenerative hematopoiesis may be suggestive of an impending relapse of AML.