Summary. Acute myeloid leukaemia (AML) with the t(8;21)(q22;q22) is deemed to be a 'good-risk' disease. 396 patients with AML at diagnosis were screened for the presence of t(8;21) and AML1/ETO fusion transcripts by cytogenetic and RT-PCR techniques respectively. 32 cases of t(8;21) were detected, all of which were also PCR positive. A further 19 cases were detected at the molecular level, predominantly but not exclusively in M1 and M2 FAB types. Approximately 12% of all new cases of AML are estimated to have AML1/ETO fusion transcripts and it is suggested that molecular screening should be performed in all cases with the possible exception of the M3 FAB type.

Summary. It has been established that cytogenetic findings at diagnosis of acute myeloid leukaemia (AML) are a powerful prognostic indicator. Patients who have the inv(16)(p13q22), closely associated with the FAB subtype M4Eo, are deemed to have good-risk disease. This subtle translocation may be difficult to detect in poor-quality metaphase preparations and if missed could lead to the incorrect assignment of risk group and influence further treatment strategies.We studied 321 patients with AML at diagnosis for the presence of inv(16)(p13q22) and CBFb/MYH11 fusion transcripts by cytogenetic and RT-PCR techniques respectively. Karyotypic analysis detected 21 cases of inv(16) (p13q22), all of which were PCR positive. A further 12 cases were detected at the molecular level only, in FAB types other than M4Eo. The observed frequencies of CBFb/MYH11 fusion transcripts in our study have been adjusted for the reported incidence of each FAB subtype and we calculate that 10 . 1% of all new cases of AMLs have molecular evidence of inv (16)(p13q22), only half of which are of the M4Eo subtype.We conclude that molecular screening for the presence of CBFb/MYH11 fusion transcripts should be mandatory in all cases of AML at diagnosis.Keywords: AML, inv(16)(p13q22), CBFb/MYH11, prognosis.The chromosomal abnormality inv(16)(p13q22) is most closely associated with the distinct subtype of acute myelomonocytic leukaemia with bone marrow eosinophilia (AML M4Eo) (Le Beau et al, 1983) and although the eosinophilia is variable it has been shown to be part of the leukaemic cell population. This pericentric inversion and the t(16;16)(p13;q22) produce a transcriptionally active fusion gene (5 0 -CBFb/MYH11-3 0 ) derived from the CBFb and MYH11 genes at 16q22 and 16p13 respectively. The reciprocal 5 0 -MYH11/CBFb-3 0 product is expressed in a proportion of cases only. The 5 0 -CBFb/MYH11-3 0 chimaeric protein is believed to induce leukaemic transformation by its abnormal interaction with the DNA-binding protein coded by the AML1 gene, thus altering target genes usually regulated by the CBFb/AML1 transcription factor complex .It has now been established from analysis of data from the MRC AML 10 trial and other international groups that AML patients with the inv(16)(p13q22) translocation, together with those in which the t(15;17)(q22;q21) or t(8;21) (q22;q22) are seen, have a favourable prognosis (Burnett et al, 1995), with the main benefit seeming to be in diseasefree survival (DFS) which leads to a better overall survival. This has been incorporated into the ongoing AML 12 trial where good-prognosis patients are spared bone marrow transplantation in first complete remission (CR). It is therefore highly desirable to define those patients who possess these favourable translocations, either by routine cytogenetic investigations or by testing at the molecular level. This may give prognostic information and also provide a means of minimal residual disease evaluation. Conventional cytogenetic methods, including synchronization and Giemsa banding, ...

Detection of BCR-ABL transcripts in chronic myeloid leukaemia (CML) is used to confirm the diagnosis and to monitor residual disease. Quantitative techniques are required to predict response to therapy or early relapse. We have evaluated an assay in which transcription-mediated amplification (TMA) of BCR-ABL and ABL transcripts is achieved using reverse transcriptase and RNA polymerase. The products are quantified in the hybridisation protection assay (HPA) using acridinium ester-labelled DNA probes and chemiluminescence. The method is a single tube procedure which uses small amounts of RNA (Ͻ500 ng/triplicate analysis), is technically simple (requiring just two waterbaths and a luminometer), rapid (total assay time Ͻ4

Summary.We have used a combination of flow cytometric assays to define multidrug resistance (MDR) positive and negative blasts in cryopreserved samples from 47 MRC trial patients with acute myeloblastic leukaemia (AML). Our primary test is a standardized assay for daunorubicin accumulation. Confirmatory assays for MDR comprised the cyclosporin modulation assay for rhodamine-123 uptake as a measure of functional P-glycoprotein and the measurement of lung resistance protein and multidrug resistance associated protein (with LRP-56 and MRPr1 respectively).57% of samples had both low accumulation and at least one positive confirmatory test. 32% were MDR negative in all four assays. 15% of patients had primary chemo-resistant disease. Resistant disease rates were 22% for confirmed MDR-positive patients and 0% for confirmed MDR-negative patients (P ¼ 0·07). Complete remission was achieved in 74% of patients, with rates of 63% in confirmed MDRpositive patients and 93% in confirmed MDR-negative patients (P ¼ 0·06). The use of a standardized method for daunorubicin uptake, combined with the use of confirmatory tests, should reduce the uncertainty that is currently characteristic of MDR evaluation in leukaemia. In comparison with daunorubicin uptake, p-gp expression, measured using MRK-16 antibody, was more closely associated with remission rates (P ¼ 0·01). This suggests an additional role for p-glycoprotein in mediating drug resistance beyond that of a drug efflux pump.

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Hairy cell leukaemia (HCL) has distinct clinical, morphological and immunophenotypic features with no recurrent cytogenetic or molecular abnormalities reported until the recent description of the BRAF V600E mutation in patients with classical HCL. The incidence of this mutation was sought in 27 patients with either classical HCL or HCL variant by an allele-specific PCR approach and findings related to morphology, cytochemistry and immunophenotype. A high degree of correlation was noted between the presence of BRAF V600E and established diagnostic criteria in 26/27 patients with HCL/HCL variant. Detection of the BRAF V600E mutation is therefore a useful adjunct in the differential diagnosis of HCL and HCL variant and highlights the value of a multifaceted approach to the diagnosis of this malignancy.

We report on a patient who developed donor-derived cutaneous T-cell lymphoma (CTCL) 4 years after successful treatment of chronic myeloid leukaemia with an allogeneic bone marrow transplant. The patient developed an eczematous rash unresponsive to topical therapy and immunosuppression. When CTCL was diagnosed in the recipient, his sibling donor had been attending his local dermatology unit with a maculosquamous rash, which proved subsequently to be mycosis fungoides. An identical pattern of donor and recipient clonality assessment and T-cell receptor gene sequencing indicated that the CTCL was probably transmitted in the bone marrow harvest. This suggests that CTCL cells circulate in the marrow at an early subclinical stage in this disease. This is the second case of donor-derived CTCL reported to date.

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