Assessment of fludarabine plus cyclophosphamide for patients with chronic lymphocytic leukaemia (the LRF CLL4 Trial): a randomised controlled trial.

BACKGROUND: Previous studies of patients with chronic lymphocytic leukaemia reported high response rates to fludarabine combined with cyclophosphamide. We aimed to establish whether this treatment combination provided greater survival benefit than did chlorambucil or fludarabine. METHODS: 777 patients with chronic lymphocytic leukaemia requiring treatment were randomly assigned to fludarabine (n=194) or fludarabine plus cyclophosphamide (196) for six courses, or chlorambucil (387) for 12 courses. The primary endpoint was overall survival, with secondary endpoints of response rates, progression-free survival, toxic effects, and quality of life. Analysis was by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number NCT 58585610. FINDINGS: There was no significant difference in overall survival between patients given fludarabine plus cyclophosphamide, fludarabine, or chlorambucil. Complete and overall response rates were better with fludarabine plus cyclophosphamide than with fludarabine (complete response rate 38%vs 15%, respectively; overall response rate 94%vs 80%, respectively; p<0.0001 for both comparisons), which were in turn better than with chlorambucil (complete response rate 7%, overall response rate 72%; p=0.006 and 0.04, respectively). Progression-free survival at 5 years was significantly better with fludarabine plus cyclophosphamide (36%) than with fludarabine (10%) or chlorambucil (10%; p<0.00005). Fludarabine plus cyclophosphamide was the best combination for all ages, including patients older than 70 years, and in prognostic groups defined by immunoglobulin heavy chain gene (V(H)) mutation status and cytogenetics, which were tested in 533 and 579 cases, respectively. Patients had more neutropenia and days in hospital with fludarabine plus cyclophosphamide, or fludarabine, than with chlorambucil. There was less haemolytic anaemia with fludarabine plus cyclophosphamide (5%) than with fludarabine (11%) or chlorambucil (12%). Quality of life was better for responders, but preliminary analyses showed no significant difference between treatments. A meta-analysis of these data and those of two published phase III trials showed a consistent benefit for the fludarabine plus cyclophosphamide regimen in terms of progression-free survival. INTERPRETATION: Fludarabine plus cyclophosphamide should now become the standard treatment for chronic lymphocytic leukaemia and the basis for new protocols that incorporate monoclonal antibodies.

Conversion of vitamin B 6 compounds to active forms in the red blood cell.

In studies with pyridoxine and other B(6) compounds in blood, the active forms pyridoxal and pyridoxal phosphate were measured by differential assays using Lactobacillus casei. Red cell uptake of tritiated pyridoxine was also measured. A new metabolic pathway for conversion of pyridoxine to active forms was demonstrated in red cells. In vivo studies in normal subjects suggested that pyridoxine was taken up by red cells where it was converted to pyridoxal phosphate and then pyridoxal, followed by gradual release of a proportion of pyridoxal into plasma. In vitro incubation of pyridoxine with blood confirmed this observation. Increasing amounts of pyridoxine were taken up and converted as the amount added to blood was increased, and only very small numbers of red cells were needed to convert appreciable amounts. Conversion was markedly inhibited at temperatures lower than 37 degrees C, and stopped altogether at - 20 degrees C.Release of pyridoxal into plasma was always directly proportional to the amount of pyridoxal formed and to the volume of plasma present. That pyridoxal phosphate was not released into plasma was demonstrated in stored blood, for pyridoxine was converted mainly only as far as pyridoxal phosphate, probably due to inactivation of the phosphatase. Pyridoxal phosphate remained in the red cells. Pyridoxine was converted when incubated with washed red cells in saline or phosphate buffer suspension (0.08 M). In saline suspension, pyridoxal formed but was not released in the absence of plasma. In phosphate buffer suspension, pyridoxal phosphate was formed but was not changed to pyridoxal, probably due to inactivation of phosphatase by excess phosphate. Pyridoxamine was converted to active forms in red cells less efficiently. Pyridoxal entered red cells rapidly, equilibrating between plasma and cells within 1 min in the same ratio as pyridoxal formed inside red cells. Pyridoxal phosphate did not enter red cells in whole blood but did so readily in washed cells in saline.

High-producer haplotypes of tumor necrosis factor alpha and lymphotoxin alpha are associated with an increased risk of myeloma and have an improved progression-free survival after treatment.

PURPOSE: To determine the effect of polymorphic variations in the tumor necrosis factor alpha (TNFalpha) and lymphotoxin alpha (LTalpha) genes on the predisposition to myeloma and the effect of these polymorphisms on response to treatment and overall survival. PATIENTS AND METHODS: Genotype distribution was determined in 63 patients with monoclonal gammopathy of uncertain significance (MGUS) and 198 patients with myeloma and compared with that in 250 age- and sex-matched population-based controls. The effect on treatment response and survival was determined in 171 myeloma patients treated with either conventional or high-dose chemotherapy. RESULTS: Comparison of the extended TNFalpha/LTalpha haplotype in the myeloma cases and controls showed a significant excess of high-producer alleles in the cases. The double heterozygotes TNF1/2 and LT10.5/5.5 were present in 35.8% of cases but in only 18% of the controls; this presence was associated with a significant increased risk of myeloma (odds ratio, 2.05; 95% confidence interval, 1.26 to 3.35). A similar odds ratio was seen in the MGUS cases, suggesting that this genotype is associated with the initiation of plasma-cell disorders rather than the progression of MGUS to myeloma. The median overall survival time of myeloma patients was 53.8 months and showed no difference with regard to TNFalpha/LTalpha polymorphic status. A trend toward an improved progression-free survival was apparent in cases with a high-producer haplotype, although this effect was seen only in patients receiving high-dose chemotherapy. CONCLUSION: Individuals with polymorphisms associated with a high production of TNFalpha/LTalpha are at a significantly increased risk of developing MGUS and myeloma. The impact of polymorphic status on overall survival is minimal, although there is a trend toward an increased progression-free survival in the high-producer group.

ChlVPP/PABlOE and radiotherapy in advanced Hodgkin's disease. The Central Lymphoma Group.

PURPOSE: The United Kingdom Central Lymphoma Group (CLG) has modified mechlorethamine, vincristine, procarbazine, and prednisone/doxorubicin, bleomycin, vinblastine, and dacarbazine (MOPP/ABVD) by substituting mechlorethamine with chlorambucil and dacarbazine with etoposide in the treatment of patients with advanced Hodgkin's disease (HD). Prednisolone is included in the bleomycin-containing combination, and the vinca alkaloids have been switched to balance the myelotoxicity of the two component regimens. PATIENTS AND METHODS: The resulting ChlVPP/PABlOE regimen is as follows: on days 1 to 14, chlorambucil 6 mg/m2 orally, procarbazine 100 mg/m2 orally, and prednisolone 30 mg/m2 orally; on days 1 and 8, vinblastine 6 mg/m2 intravenously (i.v.); on day 29, doxorubicin 40 mg/m2 i.v.; on days 29 and 36, vincristine 1.4 mg/m2 (maximum, 2 mg) i.v., and bleomycin 10 mg/m2 i.v.; on days 30, 31, and 32, etoposide 200 mg/m2/d orally; on days 29 to 43, inclusive, prednisolone, 30 mg/m2 orally. The second full cycle restarts on day 50. Treatment continues to maximum response plus two full cycles, but with a minimum of three full cycles. Radiotherapy is administered, after chemotherapy, to sites of previously bulky disease. Since 1983, 216 patients with previously untreated, advanced Hodgkin's disease (HD) have entered this study. RESULTS: The complete remission (CR) rate after chemotherapy was 73% (95% confidence interval [CI], 67% to 79%), and after additional radiotherapy was 85% (95% CI, 80% to 90%). The failure-free survival (FFS) rate at 5 years was 68% (95% CI, 61% to 74%), and the overall actuarial survival at 5 years was 78% (95% CI, 72% to 84%). The CR rate in patients in the poorer prognostic categories was high: 81% in patients with albumin levels less than 37 g/L, 79% in patients older than 40 years of age, 84% in stages IIIB plus i.v. disease, and 79% in patients presenting with B symptoms. As expected, nausea and vomiting were not major problems, although infection, often in the context of myelosuppression, complicated almost half the cases, and 29% of patients required admission at some stage for treatment of infection. CONCLUSION: In this multicenter study, ChlVPP/PABlOE produced results comparable to those reported for MOPP/ABVD, but with less nausea and vomiting. Treatment duration was shorter than in the original MOPP/ABVD regimen, and than that used in the Cancer and Leukemia Group B (CALGB) trial. It will now be compared with PABlOE alone.

Detection and quantitation of the CBFbeta/MYH11 transcripts associated with the inv(16) in presentation and follow-up samples from patients with AML.

We have developed a competitor-based RT-PCR technique which will detect and quantitate the CBFbeta/MYH11 transcripts associated with inv(16)(q22;p13) and have used it to study presentation and follow-up samples of acute myeloid leukaemia (AML). The levels of the leukaemia-specific transcripts are expressed as a ratio to a ubiquitously expressed mRNA species (Abl) which controls for RNA degradation. This technique has been applied to 75 consecutive patients presenting with either de novo AML or tMDS; 6/75 patients analysed were positive for the inv(16), all were confirmed by conventional cytogenetics. The inv(16) has a strong association with M4Eo, but we found only 2/6-positive patients to have this diagnosis (two patients with M2, one patient M1 and one patient had MDS). At presentation the levels of CBFbeta/MYH11 transcripts were 0.1-10/Abl transcript (mean 3.3/Abl transcript). Seventeen follow-up samples were available on 5/6 of these patients, and on two further patients in whom stored material was available. Following the first cycle of chemotherapy the level of transcripts was at least 10(-2) lower (0.1-10 x 10(-2)/abl transcript) than their presentation sample. Subsequent samples on these patients when in remission gave transcript levels in the range (1.0 x 10(-4) - 2 x 10(-3)/abl transcript), and three long-term follow-up samples were negative. We have developed a quantitative test which opens the possibility of predicting relapse by detecting changes in the numbers of leukaemia-specific transcripts.

Quantitation of cell-surface beta 2-microglobulin (beta 2 m) using a comparative antibody inhibition assay.

An improved immunoenzyme assay for measuring cell-surface beta 2-microglobulin (beta 2 m) is presented in which quantitation is achieved by reference to soluble beta 2 m-induced inhibition of horseradish peroxidase-labelled rabbit antibody. Some consideration is given to kinetics of binding and dissociation, and their implications for interpretation are discussed.

Expression of MHC class I and class I-like gene products on the cell membrane of mature and immature T cells.

Beta 2-microglobulin (beta 2m) constitutes the 12 kD light chain of the MHC-encoded 43-kD glycoprotein HLA-ABC molecules, which are expressed on most nucleated cells. The T6 (CD1a) antigen is expressed on thymocytes in reciprocal manner to HLA-ABC, having a similar structure to the HLA-ABC molecule. We have determined the expression of beta 2m, HLA-ABC and the T6 antigen on the cell-surface of CD1a+ and CD1a- thymocytes (defined by NA1/34 expression), and have shown that despite immunophenotypic differences between these two stages of thymic maturation, the quantity of beta 2m-associated molecules expressed was not significantly different. The nature of the heavy (alpha) chain associated with beta 2m, however, differed since HLA-ABC had largely replaced T6 on the surface of CD1a- thymocytes. We also determined the expression of beta 2m and HLA-ABC on the surface of peripheral blood CD4+ and CD8+ T-cells, and showed that the CD8+ population expressed higher levels of these antigens than CD4+ T-cells, with no detectable excess beta 2m over HLA-ABC for either subpopulation. In addition, thymocytes expressed fewer beta 2m-associated determinants than peripheral blood T-cells. These results indicate an increase in the expression of beta 2m-associated molecules with differentiation from thymic to peripheral T-cell, with a further increase in such molecules expressed on the CD8+ compared to the CD4+ peripheral T-cell subpopulation.

An UK myeloma forum phase II study of thalidomide; long term follow-up and recommendations for treatment.

Myeloma remains incurable with conventional treatment in the vast majority of patients. The introduction of thalidomide in 1999 for the treatment of relapsed disease offers the opportunity to treat patients who have developed myelotoxicity or who are refractory to conventional chemotherapy. The optimal schedule remains unresolved and only two studies have reported long term follow-up data. We report a phase II low dose escalation study of thalidomide with long term follow-up showing overall survival (OS) of 19 months and progression free survival (PFS) of 14 months. In addition we report on the side effects and toxicity and give recommendations for the use of thalidomide in the relapsed setting based upon these findings.

Detection of clonal immunoglobulin gene rearrangements in the PBPC harvests of patients with acute lymphoblastic leukaemia.

We have used a fluorescently based PCR technique to detect rearrangements in the immunoglobulin heavy chain (IgH) gene in the presentation BM of five patients with adult ALL and have looked for similar rearrangements in their PBPC. Using this approach we have been able to demonstrate clonal rearrangements in the PBPC of two of five patients. Remission BM samples taken 6-12 weeks prior to leucapheresis failed to show a clonal rearrangement in either patient. The significance of these results is discussed.

Peripheral blood stem cell transplantation in myeloma using CD34 selected cells.

We have performed nine CD34 selection procedures on peripheral blood stem cells harvested from eight patients with myeloma using the Cellpro avidin-biotin immunoaffinity column (Ceprate). They all received CVAMP chemotherapy to maximum response prior to mobilisation. Six of the patients have been transplanted using these cells, one receiving successive autografts. Median absolute cell numbers processed and retrieved were: 31.1 x 10(9) pre-column, 2.07 x 10(8) in the final product and 30.4 x 10(9) in the column waste. Mean CD34 positivity in the product was 49% (range 18.4-98) with a median CD34+ yield of 31.4% (range 21-37.8). IgH PCR was performed and seven of the eight patients were amplifiable. Of these, two were positive in the pre-column product and both of these were successfully purged with a negative result in the final, post-column product. Patients were transplanted with a median of 2.0 x 10(6) CD34+ cells/kg (range 1.5-9.4) following conditioning with melphalan 200 mg/m2. The mean time to recovery of neutrophils to > 0.5 x 10(9)/l and platelets to > 20 x 10(9)/l was 16 and 17 days, respectively. At a mean follow-up of 9 months, four of the six patients transplanted are alive, three of them in complete remission and one in a clinically stable relapse. One has died of disease relapse and one of progressive neurological problems the aetiology of which was uncertain but there was no sign of progression of their myeloma. We conclude that PBSCT using CD34 selected cells is safe and practical in myeloma following remission induction with CVAMP chemotherapy.

Waldenström macroglobulinemia. Development of diagnostic criteria and identification of prognostic factors.

To establish whether a combination of morphologic and immunophenotypic criteria could be developed to more precisely define Waldenström macroglobulinemia (WM) and prognostic factors, we retrospectively assessed the clinical and laboratory features of 111 cases of WM. Bone marrow infiltration by small lymphocytes was documented in each case; and diffuse, interstitial, nodular, and paratrabecular patterns of infiltration were documented in 58%, 32%, 6%, and 4% of cases, respectively. Ninety percent were characterized by a surface immunoglobulin-positive, CD19+CD20+CD5-CD10-CD23- immunophenotype. The median overall survival from diagnosis was 60 months; univariate analysis revealed the following adverse prognostic factors: older than 60 years, performance status more than 1, platelet count less than 100 x 10(3)/microL (< 100 x 10(9)/L), pancytopenia, and diffuse bone marrow infiltration. Associated median survival was 40, 38, 46, 28, and 59 months, respectively. Multivariate analysis revealed age, performance status, and platelet count as prognostically significant, but stratification of patients according to the International Prognostic Index had limited value. We suggest defining WM by the following criteria: IgM monoclonal gammopathy; bone marrow infiltration by small lymphocytes, plasmacytoid cells, and plasma cells in a diffuse, interstitial, or nodular pattern; and a surface immunoglobulin-positive, CD19+CD20+CD5-CD10-CD23- immunophenotype.

A new neutrophil candida killing test: chromium-51 release from Candida guilliermondii.

Neutrophil candidacidal function was measured by a chromium-51 (51Cr) release technique, using Candida guilliermondii as the test organism. The effect of varying the neutrophil:candida ratio, the time course of 51Cr release, the effect of different serum concentrations, and the reproducibility of the technique were investigated. Results from 33 experiments, using neutrophils from 35 normal donors and six patients with known neutrophil defects, show the technique to be a reliable and reproducible assay of candida killing. The chromium release assay has the advantage of being easy to perform and not liable to subjective errors.

Relative importance of renal failure and increased bone resorption in the hypercalcaemia of myelomatosis.

In order to define the relative importance of renal failure and increased bone resorption in the hypercalcaemia of myelomatosis 22 untreated patients were studied, of whom 12 were hypercalcaemic. Most patients had malabsorption of radiocalcium from the gastrointestinal tract and evidence of increased bone resorption as assessed by fasting urinary hydroxyproline/creatinine ratio. The mean OHPr/Cr ratio, however, was similar in patients with and without hypercalcaemia. Renal failure and Bence Jones proteinuria occurred more frequently in the hypercalcaemic patients. In four patients with hypercalcaemia there was an increase in OHPr/Cr after saline infusion accompanied by an improvement in renal function and hypercalcaemia. Mithramycin given to the same patients further reduced hypercalcaemia, presumably by inhibiting bone resorption. It was concluded that the hypercalcaemia of myelomatosis is due to the combination of renal failure and increased bone resorption, but that the OHPr/Cr ratio in the untreated state is a poor indicator of the degree of bone resorption in hypercalcaemic patients.

Defective neutrophil function and microbicidal mechanisms in the myelodysplastic disorders.

Neutrophil function studies have been carried out in a series of 44 patients with primary myelodysplastic syndromes (MDS). In vitro tests of phagocytosis and killing of Candida guilliermondii and Staphylococcus aureus identified 13 patients with abnormal neutrophil function at presentation and a further 10 who developed abnormalities during the course of their disease. The incidence of defective function in the five disease categories in this series was: refractory cytopenia (RC) 8/17; refractory cytopenia with sideroblastic change (RC + SC) 5/8; acquired idiopathic sideroblastic anaemia (AISA) 2/4; refractory anaemia with excess blasts (RAEB) 7/11; chronic myelomonocytic leukaemia (CMML) 1/4. Eleven of 23 patients with defective neutrophil function experienced severe infective complications; in only three of these patients were neutrophil counts less than 1 X 10(9)/l and susceptibility to infection was considered to reflect, at least partially, qualitative neutrophil abnormalities. There was no correlation between absolute neutrophil count and defective function. Abnormal overall neutrophil microbicidal activity was equally associated with impaired and normal phagocytosis. Some patients with intracellular killing defects had reduced myeloperoxidase (MPO) activities and one had reduced hexose monophosphate shunt (HMPS) activity. In two patients, whose neutrophils showed markedly impaired candidacidal activity, levamisole corrected function when added in vitro at 10(-7) M and also when administered in therapeutic dosage. It is suggested that deranged function, probably reflecting abnormalities in maturation of the granulocyte series, occurs across the myelodysplastic spectrum and that several microbicidal mechanisms may be defective.

Comparison of the effects of filtration leucapheresis and discontinuous flow centrifugation leucapheresis on granulocyte microbicidal function.

In an investigation of the in vitro phagocytic and microbicidal function of granulocytes collected by filtration leucapheresis (FL) from 18 donors and by discontinuous flow centrifugation leucapheresis (DFC) from six donors, comparison was made with the function of granulocytes obtained from the same donors by venepuncture and density gradient centrifugation over Ficoll-Isopaque (FI). No significant impairment of the phagocytosis or killing of Candida guilliermondii by either FL- or DFC-granulocytes was observed. Although the ability of FL-granulocytes to phagocytose and kill Staphylococcus aureus did not differ significantly from the function of control FI-granulocytes, DFC-granulocytes were significantly less active.

Changes in plasma beta 2 microglobulin concentrations after allogeneic bone marrow transplantation.

Plasma concentrations of beta 2 microglobulin (B2M), the light chain of the class I major histocompatibility complex, were measured serially in 26 patients undergoing allogeneic bone marrow transplantation (BMT). The concentrations fell after conditioning treatment, and recovered when the marrow was transplanted. Bacterial infection did not influence B2M concentration, but nine of 22 episodes of acute graft versus host disease were associated with raised concentrations. Increased plasma B2M concentrations were also a feature of eight episodes of chronic graft versus host disease, and these fell after treatment. Reactivation of herpes simplex, varicella zoster, or cytomegalovirus infections were also accompanied by raised B2M concentrations. Three patients with cytomegalovirus pneumonitis had high concentrations of plasma B2M, the rise starting between five and 22 days before onset of symptoms. Although it is non-specific, serial measurement of plasma B2M in patients undergoing BMT may be clinically useful in monitoring chronic graft versus host disease.

Cell surface expression of beta 2-microglobulin (beta 2m) correlates with stages of differentiation in B cell tumours.

Cell surface beta 2-microglobulin (beta 2m) densities of malignant B cells were determined by enzyme immunoassay in 97 cases of immunologically defined lymphoproliferative disease. Absolute beta 2m densities were found to depend on disease category with the lowest levels found on cells from chronic lymphocytic leukaemia (mean = 5.6 ng/10(6) cells, n = 27); atypical chronic lymphocytic leukaemia (mean = 5.9 ng/10(6) cells, n = 8); and prolymphocytoid chronic lymphocytic leukaemia variant (mean = 6.0 ng/10(6) cells, n = 16). beta 2m densities for B non-Hodgkin's lymphoma (n = 14) and B prolymphocytic leukaemia (n = 17) cases were 8.1 and 10.0 ng/10(6) cells, respectively, and the highest densities were found on cells from "late-B cell" tumours (mean = 14.3 ng/10(6) cells). Plasma cells from cases of Ig secreting tumours expressed unexpectedly low beta 2m densities (mean = 9.3 ng/10(6) cells; n = 6).

Prognostic indicators in centroblastic-centrocytic lymphoma.

The prognostic importance of ploidy and proliferative index (%S + G2) assessed by flow cytometry, mitotic and centroblast counts, and histological growth pattern were evaluated in biopsy specimens taken before treatment from 60 cases of centroblastic-centrocytic non-Hodgkin's lymphoma. Cases with a high proliferative index (greater than or equal to 18%) or DNA aneuploidy showed significantly poorer survival than those with a low proliferative index (less than 18%). A high mitotic count was also associated with a poor prognosis. On multiple regression analysis the flow cytometric assessments and mitotic counts were significant predictors of survival. Assessments of proliferative activity clearly have prognostic potential in centroblastic-centrocytic lymphoma and may permit more accurate characterisation of individual tumours.

Assessment of IgH PCR strategies in multiple myeloma.

AIMS: To compare the ability of four commonly used PCR techniques to demonstrate clonal IgH rearrangements in multiple myeloma. METHODS: Bone marrow samples (containing a minimum of 10% plasma cells) were obtained from 127 patients with confirmed multiple myeloma. Framework 3 (Fr3) PCR was performed in all cases and the Framework 1 (Fr1f) PCR, which utilises six VH family specific primers, in 98 cases. In addition, 44 cases were assessed by Fr3, Fr1f, Framework 2 (Fr2) and Framework 1 consensus (Fr1 con) PCR techniques. JH primer selection was also assessed such that each PCR strategy was performed twice in each of the 44 cases, using the JH consensus primer (JH con) alone and then repeated with an equimolar mixture of JH con, JH3 and JH6 (JH mix). RESULTS: Clonal rearrangements were demonstrated in 71 (56%) of 127 cases with the Fr3 PCR and in 52 (53%) of 98 with the Fr1f PCR. However, by using both techniques it was possible to demonstrate clonal IgH rearrangements in 92 (75%) of 122 cases. Forty four cases were assessed by all four PCR techniques; in these cases the Fr3 and Fr1f PCRs demonstrated clonal rearrangements in 26 (59%) cases with a combined yield of 34 (77%). The Fr2 and Fr1 con PCR techniques had inferior pick up rates, demonstrating clonal rearrangements in 21 (48%) of 44 cases and a combined yield of 28 (63%). The Fr2 PCR did, however, demonstrate a clonal rearrangement in one case negative by both Fr3 and Fr1f. Two additional rearrangements were demonstrated by using JH mix; one became positive by Fr3, Fr1f and Fr2 and the other positive by Fr1f, Fr1 con and Fr2. CONCLUSIONS: By utilising both the Fr3 and Fr1f PCR techniques it is possible to demonstrate definitive clonal rearrangements in the majority of patients with multiple myeloma. The Fr1 con and Fr2 PCR techniques have inferior pick up rates but may detect some additional rearrangements.

Clinicopathological correlates of IgM paraproteinemias.

IgM paraproteinemia is considered to be the major defining feature of Waldenström's macroglobulinemia (WM), but it may also occur in other B-cell lymphoproliferative disorders. In this study we have reviewed the final pathological diagnosis of 106 patients with IgM paraproteinemia investigated in our laboratories between April 1993 and May 1999. In 22 of the 106 patients (20.8%), there was no clinical or laboratory evidence of an underlying lymphoproliferative disorder, and a diagnosis of monoclonal gammopathy of undetermined significance (MGUS) was therefore made. In 60 cases (56.6%), a diagnosis of WM was made, while in the remaining 24 patients, the final diagnosis was chronic lymphocytic leukemia (n = 10), diffuse large B-cell lymphoma (n = 5), extranodal marginal-zone lymphoma (n = 3), follicular lymphoma (n = 3), and mantle-cell lymphoma (n = 3). The median paraprotein concentration in patients with WM, MGUS, and "other" lymphoproliferative disorders was 13 g/L (range, 2-54), 6 g/L (range, 3-30), and 4.5 g/L (range, 3-61), respectively. It is clear that IgM paraproteins are demonstrable in all subtypes of peripheral B-cell disorders and, although paraprotein concentrations are generally higher in WM, there is considerable overlap. Immunophenotypic criteria are therefore essential for the accurate diagnosis of WM.