Immunophenotype and DNA content of myeloma cells in primary plasma cell leukemia

Clinical features and outcomes of plasma cell leukemia: a single-institution experience in the era of novel agents

Plasma cell leukemia (PCL) is a rare hematologic malignancy with aggressive clinical and biologic features. Data regarding its prognosis with the use of the novel agents, i.e., the immunomodulatory drugs thalidomide and lenalidomide, and the proteasome inhibitor bortezomib, are limited. We retrospectively reviewed clinical outcomes, response to therapy, and survival of 17 patients seen at the Penn State Hershey Cancer Institute since the availability of novel agents (2006–2011). Twelve patients had primary PCL (pPCL), and 5 secondary PCL (sPCL). PCL was associated with aggressive clinicobiological features, such as high-risk cytogenetics, elevated serum beta-2-microglobulin and lactate dehydrogenase, International Staging System stage III, and rapid relapse after therapy. With the use of thalidomide, lenalidomide, and bortezomib in 53%, 53%, and 88% patients, respectively, median overall survival (OS) was 18 months in the whole group (95% confidence interval, 11–21 months), and 21 and 4 months in pPCL and sPCL, respectively (P=0.015). OS was inferior to that of 313 consecutive patients with multiple myeloma (MM) treated in the same period, even when compared with a subset of 47 MM with high-risk cytogenetics. Although our data are limited by the small sample size, we conclude that novel agents may modestly improve survival in patients with PCL, when compared to historical controls. Novel therapies do not seem to overcome the negative prognosis of PCL as compared with MM.

Risk stratification in the era of novel therapies

Multiple myeloma (MM) is an heterogeneous disease and this concept, together with the recent discovery of new drugs with novel mechanisms of action, will lead to the design of individualized treatments. The term "high-risk MM" includes those patients with at least one of the following features: deletion of 17p or t(4;14) or t(14;16), detected by fluorescence in situ hybridization analysis; deletion of 13q detected by conventional cytogenetics; or hypodiploidy or complex karyotype. In addition, patients with high proliferative activity of plasma cells (> or = 3%) measured by the PC labeling index or S-phase by flow cytometry as well as those with a poor response to induction therapy are also high risk. The definition of high-risk MM has been based on patients treated with conventional drugs with or without autologous transplant. However, current data suggest that novel agents can overcome the initial adverse prognosis of deletion 13q and t(4;14) but probably not that of 17p deletion, at least when using immunomodulatory drugs. Nevertheless, the number of patients analyzed is rather limited and, more important, time to progression is only available in a small number of studies. On the basis of these data, it is probably premature to mandate specific therapies on the basis of cytogenetic abnormalities. Moreover, it is possible that the more intensive therapies selected for high-risk patients may be of even greater benefit to standard-risk cases. Accordingly, at present, although we discourage treatment of high-risk patients with conventional schedules, we recommend to include them in large cooperative trials based on novel agents and performing a comprehensive genetic analysis up-front, so that the patients benefiting most from each treatment can subsequently be identified.

Prognostic factors and staging in multiple myeloma

The field of multiple myeloma prognostication is replete with studies that have shown the value of independent predictors in determining clinical outcome. It is clear that host factors and factors intrinsic to the cells are the ultimate determinants of prognosis. In the immediate period after diagnosis, those factors related to the host are likely to be more relevant, whereas with passing time factors intrinsic to the cells predominate. At a minimum, we recommend that a comprehensive molecular cytogenetic assessment be performed at diagnosis, together with conventional evaluation, including beta2-microglobulin and albumin. In addition, information on proliferative activity of plasma cells may be of value. The introduction of novel methods of prognostication should be strongly considered in all clinical trials.

Conventional diagnostics in multiple myeloma

This paper reviews the most relevant laboratory techniques currently used for the evaluation of patients with multiple myeloma (MM) and other monoclonal gammopathies. Although the bone marrow morphological examination and electrophoretic analysis of the monoclonal paraprotein still remain the 'gold standard' techniques for fast, accurate and cost-effective diagnosis, other assays such as immunophenotyping, DNA cell content and cell cycle analysis measured by flow cytometry may contribute to a better assessment of myeloma patients. Here, we will discuss not only the contribution of each technique to differential diagnosis of monoclonal gammopathies, but also the value of each parameter as prognostic factor and for monitoring treatment efficacy. In addition, possible technical pitfalls inherent to each technique will be analysed.

Primary plasma cell leukaemia: a report of 18 cases

Primary plasma cell leukaemia (P-PCL) is a variant of multiple myeloma (MM) first diagnosed in the leukemic phase, with >2000/mm(3) circulating plasma cells (PCs) and plasmacytosis >20% of the white cell count. We investigated the clinical characteristics, therapy, immunophenotype and prognosis factors of 18 patients. Common features at diagnosis were asthenia (seven patients), renal insufficiency (ten patients), bone pain (seven patients), splenomegaly or hepatomegaly (five patients). Hypercalcemia was present at diagnosis in seven patients and was the most potent poor prognosis factor (P<0.05). Most patients (16 out of 18) were treated with an anthracyclin containing regiment; complete remission was attained in one patient and partial remission in 11 patients while six patients had no response. The median survival time from diagnosis was 7 months (2--12, 95% confidence interval), but response to treatment had favorable predictive value (P<0.05). The PCs were usually positive for mature B-cell markers (PCA-1, CD38). They expressed integrins which may increase their binding to endothelial cells and thus participate in PCL physiopathology by favoring plasmocyte extramedullary spread.

Immunophenotypic Aberrations, DNA Content, and Cell Cycle Analysis of Plasma Cells in Patients with Myeloma and Monoclonal Gammopathies

We describe the immunophenotypic and gross DNA defects in 55 patients with myeloma and 50 patients with monoclonal gammopathy and review the literature on this subject (MedLine, 1994-2000). Our data confirmed previous reports indicating that in myeloma nearly all marrow plasma cells are abnormal (98.7 +/- 8.1%). In monoclonal gammopathy the fraction of abnormal plasma cells was 35.0 +/- 32.8%. In both myeloma and monoclonal gammopathy, the most frequent aberrant phenotypic features consisted of absence of expression of CD19, strong expression of CD56, and decreased intensity of expression of CD38; aberrant expression of CD10, CD20, CD22, or CD28 was observed in less than one-third of myeloma cases. The vast majority of cases had two or more phenotypic aberrations. In the DNA studies, 7% of myeloma cases were biclonal and 93% of cases were monoclonal. In those studies with only one plasma cell mitotic cycle, 37% had normal DNA content and 63% were aneuploid (hyperploid, 61%; hypoploid, 2%). The mean percentages of plasma cells in S- and G2M phases were 4.9 +/- 8.5 and 4.4 +/- 6.9%, respectively. Thirty-eight percent of cases had more than 3% of plasma cells in S phase. In monoclonal gammopathy, the DNA index of abnormal plasma cells ranged from 0.89 to 1.30 and the percentage of diploid (31%) and aneuploid (69%) cases was not different from the results found in myeloma. The differences in percentage of abnormal plasma cells in S- (7.4 +/- 8.6%) and G2M-phases (2.4 +/- 1.7%) in patients with monoclonal gammopathy were not statistically significant.

Is flow cytometric DNA content hypodiploidy prognostic in multiple myeloma?

Hypodiploid multiple myeloma is uncommon when assessed by DNA content flow cytometry, having been reported in less than 6% of patients with newly diagnosed multiple myeloma. Previous studies have shown these patients to be unresponsive to therapy and to have short survival. To address this further, we studied 349 of 504 patients eligible for Eastern Cooperative Oncology Group (ECOG) treatment trial E9486 and laboratory correlative study E9487 who had marrow mononuclear cells available for ploidy analysis. Marrow samples were studied by dual channel flow cytometry, using propidium iodide to measure the DNA content and kappa and lambda light chain antisera to identify the clonal cells. A DNA index < 0.95 was considered hypodiploid. Five patients (1.4%) were found to have hypodiploid DNA content in their marrow plasma cells. Three of the 5 patients with hypodiploid myeloma had a partial objective response to chemotherapy, which is not different from the overall objective response rate for all patients enrolled on E9486. All five patients with hypodiploid multiple myeloma died within 4 years from diagnosis, but these patients had a similar overall median survival (2.6 years) compared to the patients with diploid DNA content. Our studies confirm the poorer survival of patients with diploid versus hyperdiploid myeloma; we cannot confirm, however, the previously reported very poor outcome associated with hypodiploid myeloma using DNA content flow cytometry. Hypodiploid DNA content of plasma cells by flow cytometry may not be as ominous a factor as previously reported.

Primary Plasma Cell Leukemia: Clinical, Immunophenotypic, DNA Ploidy, and Cytogenetic Characteristics

We report on a series of 26 patients diagnosed with primary (de novo) plasma cell (PC) leukemia (PCL) in whom we analyzed the clinicobiologic characteristics of the disease together with the immunophenotype, DNA cell content, proliferative index, and numeric chromosomal aberrations of the neoplastic PC, and compared them with 664 multiple myeloma (MM) patients at diagnosis. The median age, sex ratio, and bone lesion extension were similar, but PCL cases displayed a higher prevalence of clinical stage III, extramedullary involvement, and Bence Jones cases, with fewer IgA cases than for MM patients. In addition, according to several prognostic indicators (β2-microglobulin serum level, proportion of S-phase PCs, proteinuria, calcium serum level, lactate dehydrogenase [LDH] and renal function), the incidence of adverse prognostic factors was significantly higher in PCL versus MM. Immunophenotypic expression was similar for CD38, CD138, CD2, CD3, CD16, CD10, CD13, and CD15, but PCL differed from MM in the expression of CD56, CD9 HLA-DR, CD117, and CD20 antigens. Twenty-two PCL cases were diploid and one was hypodiploid, while most MM cases (57%) showed DNA hyperdiploidy. With the fluorescent in situ hydridization (FISH) technique, 12 of 13 PCL cases displayed the numeric aberrations, −13 (86%), ±1 (57%), +18 (43%), and −X in women (25%), but they lacked several numeric aberrations usually found in MM such as +3, +6, +9, +11, and +15. PCL cases had a lower overall response to therapy than MM cases (38% v 63%, P = .01332). Among PCL patients, a trend for a worse response was observed in cases treated with melphalan and prednisone (MP) versus polychemotherapy. Overall survival was significantly worse in PCL versus MM patients (8 v 36 months,P &lt; .0001), but it was significantly better in PCL patients treated with polychemotherapy versus MP (18 v 3 months,P = .0137). By contrast, MM patients did not show significant differences in overall survival according to the treatment used, MP or polychemotherapy. Ten variables seemed to predict survival in PCL patients, but only the β2-microglobulin level and S-phase PCs retained an independent value in multivariate analysis. In summary, our study illustrates that PCs from PCL display singular phenotypic, DNA cell content, and cytogenetic characteristics that lead to a different disease evolution versus MM.

Primary Plasma Cell Leukemia: Clinical, Immunophenotypic, DNA Ploidy, and Cytogenetic Characteristics

We report on a series of 26 patients diagnosed with primary (de novo) plasma cell (PC) leukemia (PCL) in whom we analyzed the clinicobiologic characteristics of the disease together with the immunophenotype, DNA cell content, proliferative index, and numeric chromosomal aberrations of the neoplastic PC, and compared them with 664 multiple myeloma (MM) patients at diagnosis. The median age, sex ratio, and bone lesion extension were similar, but PCL cases displayed a higher prevalence of clinical stage III, extramedullary involvement, and Bence Jones cases, with fewer IgA cases than for MM patients. In addition, according to several prognostic indicators (β2-microglobulin serum level, proportion of S-phase PCs, proteinuria, calcium serum level, lactate dehydrogenase [LDH] and renal function), the incidence of adverse prognostic factors was significantly higher in PCL versus MM. Immunophenotypic expression was similar for CD38, CD138, CD2, CD3, CD16, CD10, CD13, and CD15, but PCL differed from MM in the expression of CD56, CD9 HLA-DR, CD117, and CD20 antigens. Twenty-two PCL cases were diploid and one was hypodiploid, while most MM cases (57%) showed DNA hyperdiploidy. With the fluorescent in situ hydridization (FISH) technique, 12 of 13 PCL cases displayed the numeric aberrations, −13 (86%), ±1 (57%), +18 (43%), and −X in women (25%), but they lacked several numeric aberrations usually found in MM such as +3, +6, +9, +11, and +15. PCL cases had a lower overall response to therapy than MM cases (38% v 63%, P = .01332). Among PCL patients, a trend for a worse response was observed in cases treated with melphalan and prednisone (MP) versus polychemotherapy. Overall survival was significantly worse in PCL versus MM patients (8 v 36 months,P < .0001), but it was significantly better in PCL patients treated with polychemotherapy versus MP (18 v 3 months,P = .0137). By contrast, MM patients did not show significant differences in overall survival according to the treatment used, MP or polychemotherapy. Ten variables seemed to predict survival in PCL patients, but only the β2-microglobulin level and S-phase PCs retained an independent value in multivariate analysis. In summary, our study illustrates that PCs from PCL display singular phenotypic, DNA cell content, and cytogenetic characteristics that lead to a different disease evolution versus MM.

cCD79a expression in a case of plasma cell leukemia

In the present report we analyzed the immunophenotype of the neoplastic cells in a case of primary plasma cell leukemia (PCL). We performed simultaneous analysis of bone marrow and peripheral blood samples to investigate minor phenotypic variations that could explain the tendency of a population to leave medullary compartments. No major differences were observed between the two populations. The phenotype of the malignant clone was: CD38+, CD138+, CD19-, CD56+, CD117-, CD33+, CD44 , CD49e , cCD79a+ with positive cytoplasmic stain for kappa and IgG. Our findings expands the potential uses of cCD79a to cases of PCL with atypical morphology.

DNA cell content studies in multiple myeloma

Here the current studies in cell DNA content of plasma cells (PC), from multiple myeloma (MM) patients is reviewed, focusing on two complementary aspects the detection of clonal abnormalities and the identification of the proliferative rate of PC. There is accumulating evidence that the measurement of cell DNA content by flow cytometry (FCM) is a useful parameter in the clinical evaluation of MM patients. Between 50 and 70% of MM patients display DNA aneuploidy, the majority of them being hyperdiploid. Comparing hyperdiploid with diploid patients, the former seem to display a better prognosis. Fluorescence in situ hybridization studies have confirmed that there is a high incidence of numerical chromosome abnormalities in MM and that trisomies are significantly more common than monosomies (84% vs 14%). The most frequent gains can be seen in chromosome 9 and 15 while the most common monosomies are those of chromosome 13 and X in females. The possibility of analysing the cell cycle distribution by using a propidium iodide (PI)/CD38 double staining technique may be an alternative to other more laborious methods of assessing the PC labelling index. Thus, patients with > 3% S-phase PC detected by FCM have an adverse prognosis and this parameter is one of the most important independent prognostic criteria for predicting survival in MM patients. Moreover, the number of S-phase PC, together with other prognostic factors, such as beta 2microglobulin, age and performance status can be a very useful tool for stratifying patients into groups in order to establish risk-directed therapeutic protocols.

Immunophenotype and DNA cell content in multiple myeloma

In this paper three different areas of the biology of multiple myeloma (MM) are reviewed: (1) the immunophenotypic characteristics of plasma cells (PC), (2) the changes in the immunoregulatory cells, and (3) the cell DNA content of PC. Myelomatous PC display a heterogeneous phenotype not only between different patients but also within each patient consistent with the fact that the neoplastic clone is able to undergo a certain degree of differentiation. In addition, PC generally lack surface B cell associated antigens and infrequently show reactivity for non-lineage restricted markers. The B-B4 and CD38 are the two best markers for identifying PC which are crucial for the correct assessment of other antigens by multiple staining procedures. Moreover, some of the antigens present in PC such as CD56, CD20, CD10, CD28 and SIg may have prognostic implications. Whether or not normal PC are phenotypically different from myelomatous PC remains controversial although some antigenic combinations such as CD19-/CD56++ could probably help to identify the malignant nature of PC. Both T and NK cells are markedly altered in MM patients probably reflecting a host-tumour immunological interaction. The reduction in CD4 cells correlates both with advanced clinical stage and poor survival. As far as NK cells are concerned, there is an overall increase in peripheral blood and BM in MM patients but the changes observed are heterogeneous, reflecting the existence of different NK cell subsets. This fact could explain the contradictory results observed in the literature. Accumulating evidence exists that the measurement of cell DNA content by flow cytometry is a useful parameter in the clinical evaluation of MM patients. Between 50 and 70% of MM patients display DNA aneuploidy with the majority of them hyperdiploid. Upon comparing hyperdiploid with diploid patients, the former usually display a better prognosis. The possibility of analysing the cell cycle distribution by using a PI/CD38 double staining technique may be an alternative to other more laborious methods of assessing the PC labelling index. In our experience, patients with > 3% S phase PC have an adverse prognosis and this parameter was the most important independent prognostic criteria for predicting survival.

The clonogenic precursor cell in multiple myeloma

Multiple myeloma is characterized by the monoclonal expansion of plasma cells in the bone marrow. Although the predominant cell type is the plasma cell, the initial oncogenic transformation is considered to take place in a more immature B cell. There is still much controversy about this precursor cell type. Phenotypic analysis of bone marrow and peripheral blood revealed that in multiple myeloma a great diversity exists in the phenotype of the cells considered to be involved. Because of the lack of a myeloma specific genetic lesion it is very difficult to trace back the cell in which the transforming event, leading to multiple myeloma, took place. The only real clonal marker is the idiotype of the immunoglobulin molecule expressed by the myeloma cells. With recombinant DNA technology it is now possible to produce clonal markers for each individual myeloma patient which recognize only the immunoglobulin genes expressed by the myeloma cell and its precursors. The sequences of these myeloma immunoglobulin genes do reveal a lot of information about the stage in the B-cell differentiation pathway in which the oncogenic event might have taken place. The presence of somatic mutations in a non-random fashion without intraclonal variation leads to the conclusion that the precursor myeloma cell could not possibly be a pre-B cell or stem cell but has to be a mature B cell that has been in contact with antigen and has past through the phase of somatic mutation, like a memory B cell or plasmablast.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic implications of DNA aneuploidy in 156 untreated multiple myeloma patients. Castelano-Leonés (Spain) Cooperative Group for the Study of Monoclonal Gammopathies

In this study the incidence of DNA aneuploidy in a large series of untreated multiple myeloma (MM) patients was assessed in order to determine its clinical and prognostic significance. A total of 156 MM patients were included in the study. DNA measurements were performed in all cases at diagnosis using two different flow cytometry methods: (1) propidium iodide (PI) staining on isolated nuclei, and (2) CD38/PI double staining on whole cells. The DNA ploidy status was correlated with the most relevant clinical and haematological disease characteristics. From the 156 cases analysed, 91 (58%) were aneuploid (56% hyperdiploid and 2% hypodiploid). The correlation between the two techniques on the detection of DNA aneuploidy was excellent, although CD38/PI double staining would be preferable in cases with < 5% of DNA aneuploid plasma cells (PC). Upon comparing the clinical and haematological disease characteristics of hyperdiploid versus diploid cases, the former group was characterized by a lower age, reduced incidence of anaemia, lower beta 2M levels, higher proliferative activity within the residual normal haemopoietic cells, increased expression of CD56 antigen in PC, and higher proportion of PB CD4+ T cells. In contrast, diploid cases had a higher expression of the CD10, CD20 and CD15 antigens and greater numbers of PB CD56+CD3- NK cells (P < 0.05). Circulating PC were identified in six cases, all being diploid. Overall survival was significantly longer in hyperdiploid compared to diploid MM (P = 0.02). These results show that over 50% of MM patients are aneuploid, almost all of them being hyperdiploid. This characteristic is associated with better prognosis.

Primary plasma cell leukaemia

Among 750 previously untreated patients with multiple myeloma, 27 (4%) presented with plasma cell leukaemia. All but one patient had high tumour mass and, when compared with comparable patients without leukaemia, more frequent extraosseous involvement, thrombocytopenia, high serum lactate dehydrogenase and hypodiploid plasma cells. Most patients also had complex cytogenetic abnormalities. Treatment with standard melphalan-prednisone was ineffective, with a median survival of 2 months, but more intensive chemotherapy induced responses in approximately one-half of the patients, with a median survival of 20 months. Primary plasma cell leukaemia usually results from the proliferation and extramedullary expansion of immature plasma cells and requires prompt and intensive chemotherapy.

Mouse anti-human interleukin-6 receptor monoclonal antibody inhibits proliferation of fresh human myeloma cells in vitro

Interleukin-6 (IL-6) is a major growth factor in multiple myeloma. We investigated the effect of mouse anti-human IL-6 receptor monoclonal antibody (anti-IL-6R mAb) on the in vitro proliferation of freshly isolated myeloma cells from 21 patients to evaluate the therapeutic potential. The addition of anti-IL-6R mAb inhibited more than 30% of the spontaneous proliferation of myeloma cells in 9 of 21 cases in a dose- (0.1 to 20 micrograms/ml) and time-dependent manner. The inhibitory effects of anti-IL-6R mAb did not differ significantly from that of anti-IL-6 mAb, and were correlated with the extent of the response of myeloma cells to IL-6. Flow cytometric analysis showed that all myeloma cells expressed IL-6R, whose intensity was not correlated with either the extent of response of myeloma cells to IL-6 or the inhibitory effects of anti-IL-6R mAb on proliferation of myeloma cells. Although our study showed heterogeneity in the proliferative responses of myeloma cells to IL-6 and anti-IL-6R mAb, these observations suggest the possibility of using anti-IL-6R mAbs for treating some patients with multiple myeloma whose growth depends on IL-6.

IgE plasma cell leukemia successfully treated with combination VAD (vincristine, doxorubicin, dexamethasone) and MP (melphalan, prednisolone) followed by interferon-alpha

A 69-year-old woman with IgE/kappa plasma cell leukemia (PCL) was treated with a sequential combination of VAD (vincristine, doxorubicin, dexamethasone) and MP (melphalan, prednisolone) followed by interferon-alpha (IFN alpha). A complete remission was achieved for 14 months. Maintenance therapy with IFN alpha has continued for an additional 10 months. IgE PCL is extremely rare. The biological characteristics of the myeloma cells, including surface marker, adhesion molecule, karyotype, DNA analysis, and the response to various cytokines, are presented.

DNA aneuploidy of adult T-cell leukemia cells

To clarify the biological characteristics of adult T-cell leukemia (ATL), immunophenotyping and DNA aneuploid analysis were performed in 72 ATL cases, using flow cytometric techniques. DNA aneuploidy was found in 45 cases (62.5%); the DNA index ranged from 1.03 to 2.16 (mean: 1.24). The incidence of aneuploidy in smoldering, chronic, acute, and lymphoma ATL subtypes was 20.0%, 46.6%, 76.3%, and 77.8%, respectively. The aneuploid patients had a greater tumor burden (adenopathy, hepatosplenomegaly, and leukocytosis with ATL cells), a higher level of serum LDH, and a higher incidence of hypercalcemia, compared with the diploid group. Further, unusual aberrant immunophenotypes were identified predominantly in the aneuploid group. Patients with aneuploidy had a 7.6 month median survival time (MST) with a 2 year survival rate of 24.6%, significantly worse than in the patients with diploidy, whose MST was 25.4 months with a 2 year survival of 60.1%. In some aneuploid patients, the disease often progresses from a static to an aggressive form. Thus, the determination of aneuploidy and unusual immunophenotype should be useful for detecting clinical behavior and for monitoring ATL patients, particularly in regard to such progression.

AgNORs and myeloma prognosis

The argyrophilic nucleolar organizer regions (AgNORs) were analysed in bone marrow biopsies from 80 patients with multiple myeloma (MM) at presentation. The mean AgNOR number per MM cell (AgNOR counts) and their distribution within the nucleus (configuration) were assessed. AgNOR counts were significantly associated with several recognized prognostic factors: Durie and Salmon clinical staging system (p = 0.02), percentage of plasma cells (PCs) in aspirates (p = 0.01) and in bone marrow biopsies (p = 0.0000), pattern of bone marrow involvement (p = 0.0003), calcaemia (p = 0.0005) and creatininaemia (p = 0.0003). AgNOR counts were also associated with the degree of PC differentiation (p = 0.0000). A single central cluster of 2-3 large-sized AgNORs (configuration A) was evident in most G1 MM; one cluster of 4-5 medium-sized dots or two clusters of 2-4 dots (configuration B) were seen in most G2 MM; many small-sized, scattered dots were present in G3 MM (configuration C). AgNOR counts and configuration were related to the prognosis: in the univariate analysis, the 5 year survival rate was 7% for cases with > 4.5 AgNORs/cell and 46% for cases with < or = 4.5 AgNORs/cell (p = 0.01), 53% for configuration A, 12% for configuration B and 0% for configuration C (p = 0.0000). AgNOR counts (p = 0.02) and configuration (p = 0.000) were independent prognostic variables in the multivariate analysis. The AgNOR counts were significantly higher in "fulminant myeloma" than in less aggressive cases (p = 0.002). The plasma cell labelling index (LI%), evaluated in 44 MM patients, showed significant correlation with prognosis: the 5 year survival rate was 51% for LI% < or = 1 and 17% for LI% > 1 (p = 0.02). More than 70% of patients with low LI% had low AgNOR counts and more than 70% of patients with high LI% had high AgNOR counts (p = 0.007). AgNOR counts and configuration reflect the myeloma cell mass, the degree of differentiation and the kinetics of the myeloma cells. They offer an exact evaluation of the tumour characteristics and can be useful additional parameters for MM prognosis.

Multiple myeloma: 'early' plasma cell phenotype identifies patients with aggressive biological and clinical characteristics

The immunological phenotype of bone marrow myeloma cells and peripheral blood lymphocytes was evaluated in 38 untreated myeloma patients. A striking increase of monotypic cells expressing the same light chain as the M component was observed in bone marrow from 18/38 (47%) patients. A two-colour analysis clarified that the majority of myeloma cells co-expressed plasma cell and B lymphocyte markers (cyIg, CD38, CD56 and sIg), and were regarded as early-plasma cells (early-PC). In the remaining patients, myeloma cells expressed plasma cell markers only (late-PC). Phenotype corresponded to a distinct morphological pattern: early-PC showed a lympho-plasmocytoid feature with significantly lower diameters than late-PC (12.1 v 14.8 microns, P < 0.007). Moreover, the plasma cell labelling index was significantly increased in early-PC patients (1.2 v 0.5%, P < 0.04). In peripheral blood from patients with early-PC, monotypic cells co-expressing sIg and CD38, CD56, but not CD19, were also detected. These data suggest a recirculation of early-PC. Myeloma cells maintained their phenotypic pattern during the course of the disease. This observation suggests that the degree of maturation is an intrinsic characteristic of the myeloma cell population in individual patients. The evaluation of prognostic factors, such as beta 2-microglobulin, C-reactive protein and neopterin, showed a statistically significant increase in the early-PC patients, suggesting a poor outcome. In conclusion, myeloma cell phenotype allows identification of a myeloma variant with aggressive biological and clinical characteristics.