Ingrid Arvidsson

Fluorescence in situ hybridization in combination with morphology detects minimal residual disease in remission and heralds relapse in acute leukaemia

Fluorescence in situ hybridization in combination with morphology (MGG/FISH) was used to detect minimal residual disease (MRD) in complete remission (CR) in 12 cases of acute leukaemia (six MDS‐AML, five de novo AML, one pre‐B ALL) with numerical chromosomal aberrations at diagnosis. Residual leukaemic cells could be detected in the remission bone marrows by MGG/FISH in five patients, whereas the other seven showed no abnormalities. All five patients with signs of MRD at CR relapsed in the bone marrow within 2–9 months, in contrast to two of seven with a normal finding by MGG/FISH at CR. In both these patients a second MGG/FISH analysis showed that a subpopulation of leukaemic blasts had reappeared, 4 and 5 months prior to the leukaemia becoming clinically overt. One patient suffered a CNS relapse, but without any evidence of bone marrow involvement. The remaining four patients with no evidence of MRD at CR were still in haematological remission at follow‐up after 4, 11, 12 and 13 months, respectively. We conclude that MGG/FISH seems to be a clinically useful method to detect MRD in acute leukaemia and to predict relapses, particularly when repeat studies are performed during CR.

Masked monosomy 7 in myelodysplastic syndromes is uncommon and of undetermined clinical significance

Masked monosomy 7, i.e. detected by FISH but not by conventional cytogenetics, has been reported in varying frequency in MDS. To establish the prevalence and possible clinical significance of the aberration, we studied the 123 previously karyotyped MDS patients using FISH and a DNA probe specific for chromosome 7. Metaphase cytogenetics revealed ten patients (8%) with monosomy 7 (6 RAEB and 4 RAEB-t). FISH confirmed this result and detected four more cases (4%) with masked monosomy 7 (3 RA and 1 RARS). Thus, masked monosomy 7 is less common than has been suggested, and does not seem to carry the same prognostic weight as monosomy 7 diagnosed by metaphase cytogenetics.

Neutrophil dysplasia is not a specific feature of the abnormal chromosomal clone in myelodysplastic syndromes

In order to study if dysplastic cells are part of the abnormal chromosomal clone in myelodysplastic syndromes (MDS) we used fluorescence in situ hybridization in combination with standard May-Grünwald-Giemsa morphology (MGG/FISH) to investigate the penetration of chromosomal abnormalities into dysplastic neutrophil granulocytes in five MDS patients with documented monosomy 7 or trisomy 8 in the bone marrow at diagnosis. Neutrophil dysplasia was defined as neutrophil granulocytes with extreme hypogranulation or with nuclear abnormalities of the pelgeroid type. In one patient all dysplastic cells were derived from the abnormal chromosomal clone, while in the other four cases only 6-43% of the hypogranulated neutrophils and 33-40% of the pelgeroid granulocytes exhibited the chromosomal marker. The results suggest that neutrophil dysplasia is not a specific feature of the abnormal chromosomal clone in MDS. It is not clear, however, if the disomic dysplastic cells were derived from a parallel MDS clone with a normal karyotype, or represent residual non-clonal, normal hematopoietic cells.

Fluorescence in situ hybridization for the study of cell lineage involvement in myelodysplastic syndromes with chromosome 5 anomalies

Fluorescence in situ hybridization (FISH) with a locus-specific dual DNA probe (LSI EGR-1SO/D5S23SG) for chromosome 5 was used in combination with morphology to study bone marrow cell lineage involvement of the abnormal chromosomal clone in 13 patients with deletion 5q [del(5q)], either as a sole aberration or as part of a complex karyotype, and in six cases with monosomy 5 by metaphase cytogenetics, all with complex karyotypes including 2-6 marker chromosomes. In the monosomy 5 group, only one case displayed the expected one orange and one green (1O + 1G) FISH pattern in a majority of the cells. The other five patients instead showed 1O + 2G FISH signals in 17-86% of the bone marrow cells, which is the typical pattern for del(5q). In the del(5q) group, 26-98% of the bone marrow cells exhibited 1O + 2G FISH signals. All patients showed clonal involvement of the myeloid cell lineages, including the megakaryocytes in a few cases, whereas lymphoid cells generally exhibited the normal 2O + 2G FISH pattern. No difference was seen between patients with 5q- syndrome, those with del(5q) and a complex karyotype, and the monosomy 5 group. We were thus unable to confirm the recent suggestion that B-cells are a part of the abnormal clone in MDS with del(5q). Furthermore, true monosomy 5 seems to be rare in MDS.

Differences in cell lineage involvement between MDS-AML and de novo AML studied by fluorescence in situ hybridization in combination with morphology

Abstract:u2002 We have employed fluorescence in situ hybridization (FISH) in combination with standard morphology (MGG/FISH) to identify the clonal involvement of different bone marrow cell lineages in 20 AML patients (14 MDS‐AML, 6 de novo AML). Even though the number of cells belonging to the abnormal clone varied between individual cases, the percentage of clonal blasts was similar in MDS‐AML and de novo AML patients. The erythropoietic cells appeared to be part of the abnormal clone in 13 of 14 patients with MDS‐AML, but only in 1 of 6 with de novo AML. Similarly, clonal granulocytes were detected in 13 of 14 patients with MDS‐AML, compared to 2 of 6 with de novo AML. Lymphocytes consistently displayed normal, diploid karyotype. The results suggest that it is possible to distinguish between MDS‐AML and de novo AML by the use of MGG/FISH; in de novo AML the abnormal chromosomal clone is generally confined to the immature myeloid cells, while in MDS‐AML mature granulocytes and erythroid cells are of clonal origin. It is, however, not possible to conclude that MDS‐AML is a “multipotent” type of leukaemia, since it cannot be ruled out that the chromosomally aberrant erythroid cells and granulocytes represent surviving cells from the original MDS clone

Gain of chromosome 7, which marks the progression from indolent to aggressive follicle centre lymphomas, is restricted to the B-lymphoid cell lineage: a study by FISH in combination with morphology and immunocytochemistry

In a previous fluorescent in situ hybridization (FISH) study of patients with high‐grade follicle centre lymphomas (FLCs), we often found additional copies of chromosome 7 in bone marrow (BM) cell nuclei even though obvious malignant tumour cells could not always be morphologically identified in the corresponding cell smears. This raised the question whether the gains of chromosome 7 are really confined to B‐lymphoid tumour cells or whether other cell lineages are also of clonal origin. In the present investigation we employed FISH in combination with immunomarkers and morphological studies on BM smears and lymph node imprints from seven patients with high‐grade FCLs and diffuse large B‐cell lymphomas (DLBCLs). Three out of seven BM samples were found to contain clonal CD20‐positive B‐lymphoid cells (range 0.4–96% of the cells) and no extra copies of chromosome 7 were detected in the myelomonocytoid or erythroid cells or in the CD3‐positive T lymphocytes. All seven patients showed additional copies of chromosome 7 in the lymph nodes and, again, this cytogenetic abnormality was also restricted to the CD20‐positive cells (range 0.7–80% of the cells). Thus the present findings confirm that high‐grade B‐cell lymphomas with or without BM engagement involve the CD20‐positive B‐lymphoid cells exclusively and not the T lymphocytes, erythroid or myelomonocytoid cell lineages. These findings may indicate that anti‐CD20 immunotherapy could be of value in high‐grade B‐cell lymphomas.