A new automated flow cytometry data analysis approach for the diagnostic screening of neoplastic B-cell disorders in peripheral blood samples with absolute lymphocytosis.

Currently, multiparameter flow cytometry immunophenotyping is the selected method for the differential diagnostic screening between reactive lymphocytosis and neoplastic B-cell chronic lymphoproliferative disorders (B-CLPD). Despite this, current multiparameter flow cytometry data analysis approaches still remain subjective due to the need of experienced personnel for both data analysis and interpretation of the results. In this study, we describe and validate a new automated method based on vector quantization algorithms to analyze multiparameter flow cytometry immunophenotyping data in a series of 307 peripheral blood (PB) samples. Our results show that the automated method of analysis proposed compares well with currently used manual approach and significantly improves semiautomated approaches and, that by using it, a highly efficient discrimination with 100% specificity and 100% sensitivity can be made between normal/reactive PB samples and cases with B-CLPD based on the total B-cell number and/or the sIgkappa+/sIglambda+ B-cell ratio. In addition, the method proved to be able to detect the presence of pathologic neoplastic B-cells even when these are present at low frequencies (<5% of all lymphocytes in the sample) and in poor-quality samples enriched in 'noise' events.

Interaction between clonal plasma cells and the immune system in plasma cell dyscrasias.

The term "monoclonal gammopathy" (MG) includes a group of clonal plasma cell disorders, which show heterogeneous clinical behavior. While multiple myeloma (MM) and plasma cell leukemia (PCL) are incurable malignant diseases, most patients with MG of undetermined significance (MGUS) show an indolent/benign clinical course. Evidence has accumulated which supports the role of the bone marrow microenvironment in MG. Accordingly, the survival, drug-resistance and proliferation of MM cells have been shown to be largely dependent on a supportive microenvironment. Among the different environment-associated parameters, those related to the status/activity of the immune system are particularly relevant. This review focuses on the different ways clonal plasma cells (PC) interact with the immune system in different models of MG, to characterize crucial events in the development and progression of MG. These advances may support the design of novel therapeutic approaches in patients with MG.

Incidence of phenotypic aberrations in a series of 467 patients with B chronic lymphoproliferative disorders: basis for the design of specific four-color stainings to be used for minimal residual disease investigation.

Multiparameter immunophenotypic analysis of neoplastic cells has proven to be of great help for the investigation of minimal residual disease in acute leukemias; however, its utility has not been systematically explored in B cell chronic lymphoproliferative disorders. The aim of the present study was to investigate the incidence of phenotypic aberrations in a series of 467 consecutive leukemic B cell chronic lymphoproliferative disorders through the comparison of the phenotypic characteristics of tumor vs normal peripheral blood (n = 10) and bone marrow (n = 10) B cells, in order to explore the applicability of this strategy for minimal residual disease monitoring. An additional goal of our study was to evaluate the sensitivity of multiparameter flow cytometry for the detection of minimal residual disease in leukemic B cell chronic lymphoproliferative disorders through dilutional experiments (n = 19). From the patients analyzed 382 corresponded to B cell chronic lymphocytic leukemia/small lymphocytic lymphoma (353 typical and 29 atypical); five to prolymphocytic leukemia; 13 to hairy cell leukemias; 12 to lymphoplasmacytic lymphomas; 14 to splenic marginal zone lymphomas; 22 were follicular lymphomas; and 19 mantle cell lymphomas. The following triple stainings were systematically applied to both normal and leukemic samples: FMC7/CD5/CD19, CD22/CD23/CD19, CD103/CD25/CD19, CD10/CD11c/CD19 and sIg/sIg(lambda)/CD19. Overall, 98% of the leukemic B cell chronic lymphoproliferative disorders cases displayed aberrant phenotypes at diagnosis with no significant differences being found between cases analyzed in peripheral blood vs bone marrow samples. The most common types of aberrant criteria detected included asynchronous antigen expression (92%) and antigen over-expression (54%); abnormally light scatter characteristics were found in 17% of the cases. Most of the cases studied (90%) displayed four or more phenotypic aberrations. Once patients were divided according to the different diagnostic subgroups, the overall incidence of aberrant phenotypes ranged from 79 to 80% among atypical B cell chronic lymphocytic leukemia/small lymphocytic lymphoma and prolymphocytic leukemia to 97% of follicular lymphoma and 100% of typical B cell chronic lymphocytic leukemia/small lymphocytic lymphoma, hairy cell leukemia, lymphoplasmacytic lymphomas, splenic marginal zone lymphomas and mantle cell lymphomas. Based on the aberrant phenotypes detected unique four-color stainings could be built for the specific identification of aberrant phenotypes. These include CD22/CD23/CD19/CD5 and sIg(kappa)/sIg(lambda)/CD19/CD5 for lymphocytic leukemia/small lymphocytic lymphoma and prolymphocytic leukemia, CD103/CD25 or CD22/CD19/CD11c for hairy cell leukemia, FMC7/CD22/CD19/CD103 and sIg(kappa)/sIg(lambda)/CD22/CD19 for splenic marginal zone lymphomas, CD22/CD23/CD19/CD10 for follicular lymphomas and CD10/CD22/CD19/CD5 for mantle cell lymphomas. Serial dilutional experiments showed that the sensitivity level of immunophenotyping ranges between 10(-4) and 10(-5). In summary, the present study shows that immunophenotypic analysis allows the identification of aberrant phenotypes in 98% of leukemic B cell chronic lymphoproliferative disorders and these phenotypes can be used for minimal residual disease monitoring with a sensitivity limit of 10(-4)-10(-5).

Evaluation of a CD61 MoAb method for enumeration of platelets in thrombocytopenic patients and its impact on the transfusion decision-making process.

BACKGROUND: Almost all automated hematology cell analyzers use methods based on either the impedance (PLTi) or the optical (PLTo) properties of the cells for performing platelet counts. To improve the accuracy of platelet counts in peripheral blood (PB), the use of CD61 (GPIIIa) MoAbs (ImmunoPLT method) has recently been introduced in an automated hematology blood-analyzer system (Cell-Dyn 4000, Abbott Diagnostics). STUDY DESIGN AND METHODS: A comparative evaluation was made of the accuracy and precision of the three methods currently available in the Cell-Dyn 4000 automated hematology cell analyzer for counting the number of platelets per microliter of PB in a total of 47 patients with chemotherapy-induced thrombocytopenia. A flow cytometric PB platelet count was also performed in parallel and used as an external reference. RESULTS: PB platelet counts showed a good correlation among the PLTo, CD61-ImmunoPLT, and flow cytometric methods. In contrast, the PLTi procedure usually provided an overestimation of the number of platelets per microliter. Although a good correlation was observed between the flow cytometric reference method and both the ImmunoPLT and PLTo methods, the highest degree of agreement was found for the ImmunoPLT techniques (94% vs. 67%). A comparative analysis of the PLTo and CD61-ImmunoPLT methods with regard to their value for predicting platelet transfusion needs on the basis of specific flow cytometric platelet count thresholds showed a good correlation when the cutoff level of 10,000 platelets per microL was used. In contrast, at the threshold of 20,000 platelets per microL, slight differences were observed between the PLTo and CD61-ImmunoPLT procedures for predicting transfusion needs. CONCLUSION: Such results indicate that, if the CD61-ImmunoPLT method is used in the platelet transfusion decision-making process, unnecessary platelet transfusions could be avoided in up to 17.5 percent of persons with a PLTo count of <20,000 platelets per microL.

Differences in genetic changes between multiple myeloma and plasma cell leukemia demonstrated by comparative genomic hybridization.

To analyze the genomic differences between multiple myeloma (MM) and plasma cell leukemia (PCL), a total of 30 cases were studied by comparative genomic hybridization (CGH). In five cases with a low proportion of plasma cells (PC) in bone marrow, an enrichment of PC was performed by using immunomagnetic beads conjugated with the monoclonal antibody B-B4. In 24 out of the 25 MM (96%) and in all five PCL (100%) patients DNA copy number changes were identified by CGH analysis; in the MM case without chromosomal imbalances, the immunomagnetic enrichment of PC had failed. The most recurrent changes in MM patients were gains at chromosomes 15q (48%), 11q (44%), 3q (40%), 9q (40%) and 1q (36%). By contrast, all PCL patients showed gains in 1q. Losses of chromosomal material were significantly more frequent in PCL than in MM patients (P = 0.03): losses on 13q in 80% of PCL vs 28% of MM; and on chromosome 16 in 80% vs 12%, respectively. In addition, PCL patients showed losses of 2q and 6p that were not present in MM. The CGH data show differences in chromosomal imbalances between MM and PCL.

The flow cytometric pattern of CD34, CD15 and CD13 expression in acute myeloblastic leukemia is highly characteristic of the presence of PML-RARalpha gene rearrangements.

BACKGROUND AND OBJECTIVE: Rapid identification of AML patients carrying the t(15;17) translocation for treatment decision-making is currently made on the basis of morphologic screening. However, the existence of both false positives and negatives highlights the need for more objective methods of screening AML cases and further molecular confirmation of the t(15;17) translocation. DESIGN AND METHODS: In the present study we analyzed a total of 111 AML cases in order to investigate whether immunophenotyping based on the assessment of multiple-stainings analyzed at flow cytometry could improve the sensitivity and specificity of morphologic identification of acute promyelocytic leukemia (APL) carrying the t(15;17) translocation. FISH analysis was used as a complementary technique for cases in which morphology and molecular biology yielded discrepant results. RESULTS: Concordant results between morphology and RT-PCR were found in 102/111 (91.8%) cases: 34 patients had M3/PML-RARalpha+ and 68 non-M3/PML-RARalpha- disease. Nine cases showed discrepants results. Multivariate analysis showed that the best combination of immunologic markers for discriminating between M3/PML-RARalpha+ and non-M3/PML-RARalpha- cases was that of the presence of heterogeneous expression of CD13, the existence of a single major blast cell population, and a characteristic CD34/CD15 phenotypic pattern (p<0.02). A score system based on these parameters was designed, and the 34 M3/PML-RARalpha+ cases showed a score of 3 (presence of the 3 phenotypic characteristics). In contrast, only 1 out of the 68 (1.3%) non-M3/PML-RARalpha- cases had this score, most o these latter cases (53/68, 78%) scoring either 0 or 1. Therefore, among these cases, immunophenotyping showed a sensitivity of 100% and a specificity of 99% for predicting PML/RARalpha gene rearrangements. Of the 9 cases in which morphology and molecular biology results were discrepant, four cases displayed M3 morphology without PML/RARalpha rearrangements by RT-PCR. In only one of these 4 cases did the immunophenotype score 3, this being the only FISH positive case. From the remaining five discrepant cases (non-M3 morphology while positive for PML/RARalpha) two cases had a phenotypic score of 3 and were FISH positive while the other three were negative by FISH. Upon repeating RT-PCR studies, two of these latter three cases became negative. INTERPRETATION AND CONCLUSIONS: Our results show that immunophenotyping may be of great value for quick screening of APL with PML/RARalpha rearrangements.

Detection of abnormalities in B-cell differentiation pattern is a useful tool to predict relapse in precursor-B-ALL.

Immunophenotypic investigation of minimal residual disease (MRD) has traditionally been based on the investigation of phenotypic aberrants at diagnosis to be used later as a target for MRD detection. This approach has several shortcomings (it is only applicable to patients with aberrant phenotypes, requires a diagnostic sample, and is patient-specific) and therefore a search for simpler alternatives is warranted. The present study is based on the hypothesis that in precursor-B-ALL patients the persistence of residual leukaemic cells may induce abnormalities in the precursor-B-cell compartment in bone marrow (BM) and these could be used as a criteria to predict relapse. These abnormalities may include: (1) the presence of an increase in the frequencies of immature B cells (CD34+/CD19+ or CD20-/CD19+) or (2) the existence of an altered B-cell differentiation pathway due to a blockade or to the presence of B cells outside the normal pathway. A total of 180 BM samples from 45 consecutive precursor-B-ALL patients who achieved morphological complete remission (CR) were analysed by multiparametric flow cytometry. Our results show that a significant increase in immature B-cell subsets or an altered B-cell differentiation predicts a high relapse rate (P<0.01) and a shorter disease-free survival (P<0.01). Moreover, abnormalities in either of these two criteria detected at specific time points during follow-up (end of induction, maintenance, or after treatment) were associated with a significantly shorter disease-free survival (P<0.01). In summary, the investigation of abnormalities in B-cell differentiation is a relatively simple and cheap approach for predicting relapse in precursor-B-ALL patients.

In vitro growth in acute myeloblastic leukaemia: relationship with other clinico-biological characteristics of the disease.

The in vitro growth characteristics of a large series of acute myeloid leukaemia (AML) patients and their relationship with other clinical and biological disease characteristics were analysed. Patients with AML were studied, 181 with de novo AML and 45 with secondary AML (24 myelodysplastic syndrome, sAML-MDS, 21 myeloproliferative disorder, sAML-MPD). Leukaemic colony forming units (L-CFU) were assayed by plating peripheral blood (PB) blast cells in methyl-cellulose and using LCM-PHA as stimulant. In each case parallel cultures were made with and without stimulating factors. Plating efficiency (PE) was defined as the number of clusters plus colonies/10(5) cells plated. Autonomous growth (AG) was the number of colonies plus clusters growing without stimulant. The autonomous proliferative index (API) was calculated as the number of clusters + colonies without stimulating factor divided by the number of clusters + colonies with stimulating factor. No significant differences in the PE between de novo and secondary AML were found. Autonomous growth was significantly higher in sAML-MPD. The FAB subtype M3 leukaemias displayed a significantly greater PE and a significantly lower API when compared with the other FAB subgroups (P=0.0002). Upon analysing the relationship with the immunophenotype, only CD33 expression showed a significant relationship with the in vitro growth pattern; CD33+ cases displayed a higher PE (P=0.0002) and AG (P=0.0003) than CD33- cases. When patients were grouped according to the level of rh123 efflux (MDR1) it was observed that cases with >30% elimination showed a higher AG and API than those with <30% (P=0.03). Finally we found that patients with higher API (>0.05) displayed a significantly shorter overall survival as compared with patients with API<0.05 (P=0.04). The in vitro study properties of clonogenic cells produces relevant clinical information of leukaemic cell biology in AML patients.

Functional expression of MDR-1 in acute myeloid leukemia: correlation with the clinical-biological, immunophenotypical, and prognostic disease characteristics.

Up till now, clinical data on the possible prognostic influence of multidrug resistance (MDR) in hematological malignancies have been inconsistent, probably due to technical pitfalls. Moreover, in most studies qualitative information on the presence/absence of MDR-1 expression has been used instead of quantitative results. In addition, results usually refer to the total BM population and not specifically to blast cells. In the present study we analyzed the expression of MDR-1 in a series of 50 newly diagnosed de novo AML using a double-staining technique: (a) monoclonal antibodies for the specific identification of blast cells and (b) the rhodamine-123 efflux assay, which allows a quantitative and calibrated measurement of MDR-1 function. Expression of MDR-1 was correlated with clinical, biological, and immunophenotypical disease characteristics. All patients were uniformly treated according to the AML 87/91 protocols of the Spanish Pethema Cooperative Group; the median age was 51 +/- 19 years and the FAB distribution was as follows: 2 M0, 9 M1, 9 M2, 12 M3, 11 M4, 5 M5, and 2 M6 cases. Upon grouping the 50 AML patients analyzed according to the level of rh123 elimination, it was observed that those cases with > or = 30% decrease in rh123 fluorescence displayed higher WBC counts (9 +/- 12 vs 37 +/- 73 x 10(9)/l, p = 0.02) and platelet numbers (94 +/- 11 vs 35 +/- 25 x 10(9)/l, p = 0.02), together with a higher incidence of extramedullary involvement (35% vs 24%, p = 0.02). Half of the patients (47%) displaying a low rh123 elimination (< 30%) showed M3 morphology, while among the 33 patients with a higher rate of rh123 elimination (> or = 30%), only four (12%) corresponded to the M3 morphological subtype (p = 0.0006). From the immunophenotypic point of view, a low rate of rh123 elimination was associated with a lower expression of HLADR antigen (p = 0.003) and a higher expression of CD117 (p = 0.01). Regarding the possible prognostic influence of MDR1 expression, we found that a high rate of rh123 elimination (> 30%) was associated with a tendency towards poor disease outcome, illustrated by both a lower complete remission rate with the first cycle of chemotherapy (36% vs 56%) and a lower median disease-free survival (22 months vs median DFS not reached), although differences did not reach statistical significance (p = 0.1 in both comparisons). This data shows that although MDR-1 can be a relevant parameter in the evaluation of AML patients, larger series of patients using appropriate techniques for specifically analyzing the MDR of blast cells will be necessary in order to establish the final clinical value of this parameter.

Immunophenotyping investigation of minimal residual disease is a useful approach for predicting relapse in acute myeloid leukemia patients.

A high complete remission rate is currently achieved in patients with acute myeloid leukemia (AML). However, many patients eventually relapse due to the persistence of low numbers of residual leukemic cells that are undetectable by conventional cytomorphologic criteria (minimal residual disease [MRD]). Using immunophenotypic multiparametric flow cytometry, we have investigated in sequential studies (diagnosis and follow-up) the impact of MRD detection on the outcome of 53 AML patients that had achieved morphologic remission with standard AML protocols and displayed at diagnosis an aberrant phenotype. Patients were studied at diagnosis with a panel of 35 monoclonal antibodies in triple staining combinations for detection of aberrant or uncommon phenotypic features. According to these features, a patient's probe was custom-built at diagnosis for the identification of possible residual leukemic cells during follow-up. The level of MRD at the end of induction and intensification therapy correlated with the number of relapses and relapse-free survival (RFS). Thus, patients with more than 5 x 10(-3) residual cells (5 residual cells among 1,000 normal bone marrow [BM] cells) identified as leukemic by immunophenotyping in the first remission BM showed a significant higher rate of relapse (67% v 20% for patients with less than 5 x 10(-3) residual cells; P = .002) and a lower median RFS (17 months v not reached; P = .01). At the end of intensification, with a cut-off value of 2 x 10(-3) leukemic cells, AML patients also separated into two distinct groups with relapse rates of 69% versus 32% (P = .02), respectively, and median RFS of 16 months versus not reached (P = .04). In addition, overall survival was also significantly related to the level of residual cells in the marrow obtained at the end of induction and particularly after intensification therapy (P = .008). Furthermore, we have explored whether residual disease was related with the functional expression of multidrug resistance (MDR-1) at diagnosis as assessed by the rhodamine123 assay. Patients with > or =5 x 10(-3) residual leukemic cells at the end of induction therapy had a significantly higher rhodamine-123 efflux (mean, 56% +/- 24%) than those with less than 5 x 10(-3) residual cells (mean, 32% +/- 31%; P = .04). Finally, multivariate analysis showed that the number of residual cells at the end of induction or intensification therapy was the most important prognostic factor for prediction of RFS. Overall, our results show that immunophenotypical investigation of MRD strongly predicts outcome in patients with AML and that the number of residual leukemic cells correlates with multidrug resistance.

Association between trisomy 8 and the immunophenotype of blast cells from acute leukemias secondary to a myelodysplastic syndrome or chronic myeloproliferative disorders.

In the present study we have used FISH to analyze the incidence of trisomy 8 in acute leukemias following either a primary myeloproliferative disorder (MPD) or a myelodysplastic syndrome (MDS) and correlated it with both the immunophenotype and the cell-cycle distribution of the leukemic blast cells. Six of the 21 (28%) acute leukemias studied displayed trisomy 8 by FISH. The number of trisomic cells in these cases ranged from 20 to 84%, with a mean of 46 +/- 24%. Trisomy 8 was associated with a homogeneous population of leukemic cells, phenotypically characterized by CD34+/HLADR+/CD13+/CD33+/CD11b-/ CD15-/CD14-. No significant differences were observed on the proliferative rate of cases with trisomy 8, as compared with blast cells from the remaining patients. Overall, our findings suggest that in acute leukemias secondary to MPD or MDS, trisomy 8 is associated with a blockade of myeloid maturation at an early step of the differentiation process.

[Syndrome of abnormal chromatin clumping in leucocytes with a high fraction of bone marrow cells in S-phase and in vitro autonomous growth]. / Síndrome de condensación anómala de la cromatina de los leucocitos con elevada fase de síntesis medular y crecimiento autónomo in vitro.

Syndrome of abnormal chromatin clumping in leucocytes syndrome (ACCLS) is an uncommon entity which shares clinical and biological features with the myelodysplastic (MDS) and chronic myeloproliferative syndrome. In fact, as some authors consider ACCLS a new type of MDS, others maintain that it is in Ph'negative/bcr-abl negative chronic myeloid leukaemia. A new case of ACCLS appeared in a 68 year old woman, who presented with anaemic symptoms, bleeding and recurrent infections, and a haematological picture including progressive macrocytic anemia, thrombocytopenia and leuco-erythroblastosis. Marrow hypercellularity with granulocytic hyperplasia, and mature granulocytes presenting nuclear hyposegmentation and large peripheral blocks of chromatin separated by clear zones were the characteristic features of this case. No cytogenetic abnormalities were found and DNA flow-cytometry content was normal (euploid), supporting the thought that a disequilibrium exists in the hetero-chromatin/eucromatin ration in AACLS. Reverse PCR for bcr-abl transcripts was negative. The cell-cycle-phase analysis showed a high fraction of S-cells in the bone marrow (27%) in contrast to a very low S-phase (0.2%) in the peripheral blood, pattern that is different from both CMML and CML. In vitro clonogenic assays showed a high colony forming capacity and a certain grade of autonomous proliferation of the bone marrow cells, which is reminiscent of the CMML growth behaviour in culture. The patient was treated with vitamin D3, low dose Ara-C, prednisone and hydroxyurea until her demise, fifteen months after diagnosis. In total, the patient received 47 units of packed cells and 114 of platelet concentrates, and was transfused only when she presented anaemic or hemorrhagic symptoms. These clinical and haematological features suggest that ACCLS is a distinct entity that should be considered a sixth type of MDS, beside CMML, with which it has much in common.

Value of colony forming unit-granulocyte macrophage assay in predicting relapse in acute myeloid leukaemia.

AIM: To evaluate the validity of the colony forming unit-granulocyte macrophage (CFU-GM) assay for predicting relapse in patients with acute myeloid leukaemia (AML). METHODS: The study population comprised 32 patients with AML in remission, followed for a median of 18 months. A mean of four studies was carried out per patient. Three patterns of in vitro growth based on the number of CFU-GM in normal bone marrow were defined: 1 = normal (normal number of CFU-GM and a cluster:colony ratio < 2); 2 = hypoplastic (low number of CFU-GM and a cluster:colony ratio < 2); 3 = anomalous (low or normal number of CFU-GM and a cluster:colony ratio > 2). RESULTS: Eleven patients relapsed, all of whom had previously displayed an abnormal CFU-GM pattern: anomalous in nine and hypoplastic in two. The remaining 25 patients were in complete remission at the time of writing, 16 of whom had a normal growth pattern. The other nine had anomalous (eight patients) or hypoplastic (one patient) growth. The latter may be false positive results. The in vitro growth pattern was not constant during follow up analysis. All 15 patients in whom the growth pattern switched from abnormal to normal remain in complete remission. By contrast, of the five cases in whom the pattern changed from normal to abnormal, three have relapsed and the other two had other indicators of relapse. The growth pattern remained unchanged in the remaining 16 patients. CONCLUSION: The present data show that the sequential investigation of the CFU-GM growth pattern may be of value in predicting relapse in patients with AML.

Phenotypic changes in acute myeloid leukaemia: implications in the detection of minimal residual disease.

AIM: To explore the role of phenotypic changes as possible limiting factors in the immunological detection of minimal residual disease in patients with acute myeloid leukaemia (AML). METHODS: 20 relapses were evaluated, with special attention to changes in the criteria used for the definition of a phenotype as "aberrant". In all cases the same monoclonal antibody and fluorochrome were used at diagnosis and in relapse. RESULTS: Six out of the 16 patients showed aberrant phenotypes at diagnosis. At relapse, no changes in the aberrant phenotypes were detected in most of the patients; nevertheless, in two of the four patients with asynchronous antigen expression this aberration disappeared at relapse. At diagnosis in both cases there were already small blast cell subpopulations showing the phenotype of leukaemic cells at relapse. Ten out of the 16 cases analysed showed significant changes in the expression of at least one of the markers analysed. CONCLUSIONS: At relapse in AML the "leukaemic phenotypes" usually remained unaltered, while other phenotypic features--not relevant for distinguishing leukaemic blast cells among normal progenitors--changed frequently; however, they were not a major limitation in the immunological detection of minimal residual disease.

[Results of a series of 104 consecutive bilateral bone marrow biopsy specimens in lymphoproliferative disorders]. / Resultados de una serie de 104 biopsias de medula ósea bicrestales consecutivas en síndromes linfoproliferativos.

PURPOSE: To establish the incidence of discordance in a series of bilateral bone marrow biopsies (b-BMB) in lymphoproliferative disorders and to determine whether this might lead to changes in the present treatment of each patient. MATERIAL AND METHODS: Between March/1988 and February/1995, 89 patients underwent bilateral bone marrow biopsy (104 b-BMB). Seventy-six underwent one b-BMB; 11 two b-BMB and 2 patients three b-BMB. Sixty-eight b-BMB were done at diagnosis of the disease and 36 for reassessment prior to ABMT. The distribution of the b-BMB by diagnosis was as follows: 54 non-Hodgkin's lymphoma (NHL) -23 low grade NHL and 31 intermediate/high grade NHL-, 44 Hodgkin's disease (HD), 4 multiple myeloma (MM), 1 splenic lymphoma with villous lymphocytes and 1 MM+HD. Specimens were obtained under local anaesthesia with a Jamshidi gauge 8 needle. The biopsies were fixed, decalcified, embedded in paraffin wax and the section cuts were stained (haematoxylin and eosin, Giemsa, Wilder--reticulin--and Masson--collagen--). RESULTS: There was discordance in 5 of the 104 b-BMB (4.8%), but only in four of them was this related to the presence of bone marrow disease, so that incidence falls to 3.8%. Three of them were obtained at diagnosis of the disease (low grade NHL, high grade NHL and HD) and one during reassessment before ABMT. On considering only the specimens that had bone marrow infiltration (19 cases: 14 at diagnosis and 5 in reassessment before ABMT), the absence of concordance in four of them implies that if only unilateral biopsy had been carried out, up to 21% of the cases might have been missed. In one of these patients (HD) this finding led us to replace autologous bone marrow transplantation by autologous peripheral stem cell transplantation. CONCLUSION: On the basis of these data, the use of bilateral bone marrow biopsy specimens may be justified in lymphoproliferative disorders, both at the time of diagnosis and in reassessment prior to ABMT--when the bone marrow was initially infiltrated.