Circulating Malignant Clonal Cells in Peripheral Blood of Patients with Myelodysplastic Syndrome: Verification by Interphase Fluorescent in Situ Hybridization Study and Its Correlation with Bone Marrow Clonal Cells.

Bone marrow (BM) cells are believed as the source neoplastic cells in patients with myelodysplastic syndrome (MDS). We examined whether the clonal proliferating pattern in peripheral blood truly reflects clonal haemopoiesis in the bone marrow.

We performed interphase fluorescence in situ hybridization (iFISH) with peripheral blood mononuclear cells in MDS patients with clonal abnormalities detected using iFISH and conventional G-banding. Nine patients were included in the study: 3 at initial diagnosis (patient 4, 6 and 9), 2 at follow up without stem cell transplantation (SCT) (patient 1 and 3) and 4 at follow-up after SCT (patient 2, 5, 7 and 8). We used 5 types of probes (Vysis Inc.) to detect 5q, 7q, 8, 20q and 1q abnormalities. The results were compared with iFISH results of bone marrow at the initial diagnosis and at the follow up (if any).

Same clonal abnormalities were detected in similar quantity in the initial bone marrow, the follow-up bone marrow (if any) and the peripheral blood mononuclear cells of 3 patients at initial diagnosis and 2 follow up patients who did not received SCT. The follow up bone marrow biopsies of those 2 without SCT showed disease progression to advanced disease (RAEB-1 to RAEB-2, patient 1) or persistent disease (RCUD-RA, patient 3). One patient who received SCT (patient 2) had the same clonal abnormality (trisomy 8) in peripheral blood mononuclear cells at the follow up as in the bone marrow cells at the initial diagnosis in a very reduced dose (69.0% vs. 2.5%). Another patient with SCT (patient 5) did not showed clonal abnormality in the bone marrow and the peripheral blood at the follow up, with bone marrow biopsy findng of poor engraftment. The other 2 patients with SCT (patient 7 and 8) did not showed the clonal abnormality in the peripheral blood mononuclear cells, which were observed in the initial bone marrow. Their bone marrow biopsies showed complete remission of the disease. The results are specified in Table 1.

Using interphase FISH technique, we observed the same clonal abnormalities in the peripheral blood mononuclear cells as in the bone marrow mononuclear cells in the cases of initial diagnosis or the cases with disease progression or persistent disease. The quantity of clonal abnormality was also similar in between. The clonal abnormalities were not detected in the peripheral blood in the cases with stem cell transplantation and improved bone marrow findings. We concluded that the type and the quantity of clonal abnormalities in peripheral blood mononuclear cells well reflect those of bone marrow and bone marrow morphology. Our results demonstrate the potential role of disease monitoring with peripheral blood in the MDS patients, even when not accompanied by invasive bone marrow exam.

Table 1.

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*SCT: Stem cell transplantation at least 14 days before collection of peripheral blood

^¢″-: not tested

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No relevant conflicts of interest to declare.