Distinct patterns of novel gene mutations in poor-prognostic stereotyped subsets of chronic lymphocytic leukemia: the case of SF3B1 and subset #2.

Recent studies have revealed recurrent mutations of the NOTCH1, SF3B1 and BIRC3 genes in chronic lymphocytic leukemia (CLL), especially among aggressive, chemorefractory cases. Nevertheless, it is currently unknown whether their presence may differ in subsets of patients carrying stereotyped B-cell receptors and also exhibiting distinct prognoses. Here, we analyzed the mutation status of NOTCH1, SF3B1 and BIRC3 in three subsets with particularly poor prognosis, that is, subset #1, #2 and #8, aiming to explore links between genetic aberrations and immune signaling. A remarkably higher frequency of SF3B1 mutations was revealed in subset #2 (44%) versus subset #1 and #8 (4.6% and 0%, respectively; P<0.001). In contrast, the frequency of NOTCH1 mutations in subset #2 was only 8%, lower than the frequency observed in either subset #1 or #8 (19% and 14%, respectively; P=0.04 for subset #1 versus #2). No associations were found for BIRC3 mutations that overall were rare. The apparent non-random association of certain mutations with stereotyped CLL subsets alludes to subset-biased acquisition of genomic aberrations, perhaps consistent with particular antigen/antibody interactions. These novel findings assist in unraveling specific mechanisms underlying clinical aggressiveness in poor-prognostic stereotyped subsets, with far-reaching implications for understanding their clonal evolution and implementing biologically oriented therapy.

Analysis of the turin umbilical cord blood bank registry.

BACKGROUND: The polymorphic nature of the HLA system reduces a patient's probability of finding an HLA-compatible unrelated bone marrow (BM) donor, even though more than 6 million individuals are enrolled in international registries. Recently, umbilical cord blood (UCB) has been successfully employed as a source of HPCs. The use of such cells reduces the risk of GVHD and allows transplants with one or two HLA mismatches. UCB represents an expensive resource: therefore, it is necessary to carefully manage the UCB unit inventory. STUDY DESIGN AND METHODS: The current study analyzed the genetic heterogeneity of HLA-A, -B, and -DR gene frequencies between pools of UCB and unrelated-donor BM in the Piedmont (an administrative region of Italy). An Italian hematology patient's probability of finding complete or partial matches as a function of donor pool size was determined by considering subsamples randomly selected from the local unrelated BM donors. RESULTS: The HLA gene frequencies in UCB and unrelated-donor BM pools were not significantly different. The search simulation, based on actual HLA phenotypes, showed that the percentage of Italian patients matched with an HPC unit increases remarkably if 1 or 2 mismatches are accepted, reaching a proportion of 90 percent with an inventory of only about 500 units, while the increment is not so remarkable if the number of UCB units is greater. CONCLUSION: To optimize economic resources and to be internationally competitive, UCB banks should aim to increase the genetic heterogeneity of their units rather than increasing the UCB inventory, acquire efficient quality control systems, and acquire and preserve UCB units with a greater number of nucleated cells.

Microsatellite instability is associated with the histological features of the tumor in nonfamilial colorectal cancer.

Replication errors (RERs) at microsatellite loci were examined in 46 specimens of nonfamilial colorectal cancer. Somatic microsatellite alterations in at least two genetic loci, D11S904, D13S175, D2S123, and D10S197, consistent with a RER(+) phenotype were found in four cases (8.7%). Six additional cases (13%) showed alterations at a single locus. Mucinous differentiation was observed in 3 of 4 (75%) adenocarcinomas with a RER(+) phenotype and only in 19% (8 of 42) of RER(-) adenocarcinomas (P < 0.05). A distinct cap of inflammatory cells at the advancing edge of the tumor and Crohn's-like reaction in peritumoral stroma were histologically identified in 50 and 25% of RER(+) and in 5 and 0% of RER(-) tumors, respectively (P < 0.05). Also, the plexiform pattern of growth of carcinoma turned out to be significantly associated with the RER(+) phenotype (P < 0.05). Mucinous differentiation and stromal inflammatory reactions are frequent features of hereditary nonpolyposis colorectal cancer in which germ-line mutations of mismatch repair genes cause genetic instability. Our results indicate that a link exists between such histological features and somatic genetic instability consistent with a RER(+) phenotype also in nonfamilial colorectal cancer.

Role of prolactin in the in vitro development of interleukin-2-driven anti-tumoural lymphokine-activated killer cells.

Exogenous prolactin (PRL) has been shown to synergize with low-dose interleukin-2 (IL-2) and induce the proliferation and lymphokine-activated killer (LAK) maturation of natural killer (NK) cells. PRL itself can also generate LAK activity. Here we show that its local production occurs during, and is necessary for, LAK development. IL-2-stimulated peripheral blood mononuclear cells (PBMC) and purified NK cells were exposed to anti-human (h)PRL antiserum, and residual LAK activity was measured on day 7 against the promyelocytic leukaemia cell line HL-60. Inhibition of LAK activity was much more evident in PBMC compared with NK cell cultures (47% decrease. P - 0.013 and 18.5% decrease. P = 0.048, respectively). Up-modulation of a 32S-methionine-labelled 27,000 MW protein was detected in the lysates and supernatants of IL-2-stimulated PBMC immunoprecipitated with an anti-PRL antiserum. By contrast, the cytoplasmic PRL immunoreactivity observed in freshly isolated NK cells and in IL-2-stimulated, but not unstimulated, NK cell cultures was not associated with PRL gene activation, and can thus be referred to internalized PRL. Preferential re-uptake of externally derived PRL by IL-2-stimulated NK cells was also indicated by up-modulation of the PRL receptor. These data, as a whole, indicate that the PRL promotion of LAK differentiation is mainly mediated by paracrine secretion, with a minor contribution from internalized PRL.

Intestinal T-cell lymphoma with massive tissue and blood eosinophilia mediated by IL-5.

A case of enteropathy associated T-cell lymphoma (EATCL) in a 62-year-old female with a previous history of coeliac disease, complicated during the clinical course by massive blood and tissue eosinophilia is described. The patient's serum contained a factor capable of stimulating the in vitro growth of eosinophilic colonies (CFU-Eo), that was absent in the serum of normal donors. We suggest that such factor was Interleukin-5 (IL-5), as indicated by the presence in the monoclonal tumor T cells of IL-5 encoding mRNA, usually absent in the normal enterocytes of the jejunum.

Long-term results of alpha interferon as initial therapy and splenectomy as consolidation therapy in patients with hairy cell leukemia. Final report from the Italian Cooperative Group for HCL.

PURPOSE: In 1987 the Italian Cooperative Group for the Study of hairy cell leukemia (HCL) started a prospective trial with the following three major aims: 1) to confirm the effectiveness of alpha-IFN as first-line treatment; 2) to assess the usefulness of splenectomy as consolidation treatment in patients achieving a satisfactory partial remission (PR) with alpha-IFN, and 3) to explore whether splenectomy in patients achieving complete remission (CR) with alpha-IFN can reduce the risk of relapse after discontinuation of the drug. PATIENTS AND METHODS: One-hundred seventy-seven patients with histologically-confirmed HCL were registered in the HCL88-A trial between December 1987 and January 1992. Inclusion criteria included no previous treatment and age less than 66 years. All patients received total doses of 3 MU of alpha-IFN daily for 12 months except for those who achieved early CR and would stop treatment after 6 or 9 months. Patients could be treated with different alpha-IFNs. At the time of the present analysis, 166 patients (93.8%) were fully evaluable. RESULTS: Treatment of HCL patients with alpha-IFN at the onset of the disease resulted in 28 CR (16.9%), 103 PR (62.0%), and 27 Minor Remissions (MR) (16.3%). Patients treated with different alpha-IFNs achieved similar results: the overall response rate (CR + PR + MR) was 92.7%, 97.2%, and 95.3% for patients treated with r-alpha-2a, r-alpha 2b, and alpha-N1, respectively. The presence of a leukemic phase and a poor performance status were associated with a statistically significant lower response rate. Patients who were randomly assigned and underwent splenectomy after achieving a PR had a better but not significant 4-year progression-free survival than cases randomized for observation (53% vs. 22%, p = 0.116). Overall, 5 patients died after study entry, with an actuarial 5-year survival rate of 96% for the entire group of 166 patients. After a mean follow-up time of 38 months, only one second malignancy has been recorded. CONCLUSIONS: Initial therapy with alpha-IFN, regardless of the type of alpha-IFN used, induces satisfactory responses in the majority of patients with HCL, but in most instances discontinuation of treatment results in recurrence of disease. In most cases alpha-IFN improves the performance status of patients and favors a satisfactory bone marrow recovery and thus could still play a role in the initial management of the disease. Although splenectomy following alpha-IFN could prolong the progression free survival, its use should be restricted to selected cases.

Immunoglobulin light chain restriction and clonal rearrangement in nodular paragranuloma.

B-cell clonality was demonstrated in a typical nodular paragranuloma case (NP) by both immunoglobulin (Ig) surface analysis and Ig genes rearrangement studies. On frozen sections, immunostaining for Ig light chain expression revealed a clear-cut predominance of Ig lambda-expressing cells, recognizable as both small lymphocytes and lympho-histiocytic (L&H) cells. Accordingly, molecular analysis of the Ig genes showed a monoclonal rearrangement of the lambda chain gene, although no specific pattern of heavy chain gene rearrangement could be detected by JH analysis. The C lambda rearranged band was identified with two different restriction enzymes, excluding the hypothesis of a genomic polymorphism. Furthermore, the C kappa gene was almost completely deleted, indicating that the developmental hierarchy of Ig genes rearrangement has been respected. The molecular pattern of the C lambda hybridizing band was consistent with monoallelic rearrangement of almost the entire DNA sample, indicating that clonal proliferation was not limited to L&H cells, but also involved surrounding lymphocytes. This finding is in keeping with the immunohistochemical evidence of a lambda light chain restriction on both L&H cells and small lymphocytes, pointing to a close relationship between these two cell types. Our results as a whole suggest that L&H cells and B lymphocytes share a common origin and may both be involved in clonal proliferation in NP.

Cytokine gene expression in B-cell chronic lymphocytic leukemia: evidence of constitutive interleukin-8 (IL-8) mRNA expression and secretion of biologically active IL-8 protein.

To extent our knowledge on the cytokines possibly involved in the pathophysiology of B-cell chronic lymphocytic leukemia (B-CLL), the mRNA expression of a panel of 10 cytokines was investigated on purified B-CLL cells using a reverse-transcriptase polymerase chain reaction method. Whereas negative RT-PCR signals were recorded for interleukin-1 alpha (IL-1 alpha), IL-2, IL-3, IL-4, IL-5, IL-7, tumor necrosis factor beta (TNF beta), and granulocyte-macrophage colony-stimulating factor, we detected the expression of IL-1 beta, IL-6 and TNF alpha. Furthermore, the constitutive expression of IL-8 mRNA was observed in all 17 B-CLL samples analyzed. mRNA expression was associated with the capacity of the leukemic cells to release IL-8 both constitutively (4.6 +/- 8.1 SD ng/mL) and, to a further extent, after stimulation (14.5 +/- 19.4 ng/mL). The circulating levels of IL-8 were also evaluated in 12 untreated B-CLL sera samples and the overall mean level was significantly higher (P < .01) than in normal sera. In addition, supernatants of purified B-CLL cells cultured in the presence of 12-O-tetradecanoylphorbol-13-acetate showed chemotactic activity towards neutrophils; this activity was neutralized in the presence of an anti-IL-8 antiserum. The mRNA for IL-8 was absent in five B-cell preparations from hairy cell leukemia cases and in four B-cell lines. Normal tonsil CD5+ B cells showed a low expression of IL-8 mRNA only in two of the nine preparations tested and the overall quantity of IL-8 released by these cells after 3 days' incubation was significantly lower compared with that released by B-CLL cells (0.4 +/- 0.3 and 1.6 +/- 0.9 ng/mL under basal and stimulated conditions, respectively). These findings point to an involvement of a member of the proinflammatory chemokine supergene family in human CD5+ B lymphocytes. The different IL-8 behavior observed between B-CLL cells and their normal counterpart is likely to reflect an activation state of the leukemic population.

Molecular evaluation of clonal remission in hairy cell leukemia patients treated with 2-chlorodeoxyadenosine.

Several reports have documented complete and long-lasting remissions in hairy cell leukemia (HCL) patients after a single one-week course of 0.1 mg/kg/d of 2-Chlorodeoxyadenosine (2-CdA) administered by intravenous infusion. In these studies the evaluation of the clinical response was based on physical examination, blood cell counts, as well as cytochemical and immunological detection of residual leukemic cells. Since HCL is a chronic lymphoproliferative disorder characterized by the expansion of monoclonal B cells, analysis of the configuration of the immunoglobulin gene regions represents a valuable tool towards a more accurate monitoring of treatment response. We hereby describe the molecular assessment of the neoplastic clone in six HCL patients treated with 2-CdA; in five of them a disappearance of the rearranged bands could be documented in bone marrow cells aspirated between 2 and 21 months after a single course of continuous infusion 2-CdA. The last HCL case analyzed, revealed molecular persistence of the neoplastic clone. In all cases but one, the molecular evaluation was in agreement with the definition of clinical response based on conventional analysis. This study demonstrates that HCL patients treated with 2-CdA show a high incidence of molecularly-defined complete remissions, the likelihood of which is much greater than for patients treated with Interferon alpha.

Preferential clustering of chromosomal breakpoints in Burkitt's lymphomas and L3 type acute lymphoblastic leukemias with a t(8;14) translocation.

We have analyzed the type of MYC/IG heavy-chain locus (IGH) rearrangement present in 15 patients affected by t(8;14)-positive primary Burkitt's lymphoma or acute lymphoblastic leukemia of the L3 type in an attempt to map in detail the locations of the chromosome 8 and chromosome 14 breakpoints. The almost constant position of the chromosome 8 breakpoint (within or immediately 5' of the MYC gene) together with two distinct clusters of breakpoints on chromosome 14 resulted in two main types of MYC/IGH (present in 12 of 15 cases). In the first type (six cases), the MYC gene or at least its coding portion was joined with the JH region on chromosome 14, whereas in the second, present in another six cases, the MYC gene and the C alpha I region were juxtaposed. Physical linkage between the translocated MYC and a known enhancer element of the IGH locus is the common feature in the two types of rearrangement, suggesting that a high-level constitutive expression plays a prominent role in MYC activation. Interestingly, the chromosome 14 break site within the switch alpha 1 region, which has been only occasionally described in other cases, is present in 40% of our patients, suggesting the existence of preferential breakpoint cluster regions in cases of similar geographic origin.

Phenotypic analysis of hairy cell leukemia: "variant" cases express the interleukin-2 receptor beta chain, but not the alpha chain (CD25).

Hairy cell leukemia (HCL) is a B-cell chronic lymphoproliferative disorder in which the pathologic cells show a strong expression of CD25 (interleukin-2 [IL-2] receptor alpha chain or p55). "Variant" cases of HCL, characterized by hyperleukocytosis, neoplastic elements with a prominent nucleolus and a higher nucleo/cytoplasmic ratio, and an easily obtained bone marrow aspirate, lack surface CD25 determinants. Limited information is available on the expression of the IL-2 receptor beta chain (p75) on normal and neoplastic B cells. In this study, we have assessed by immunofluorescence and mRNA analysis the presence of the IL-2 receptor alpha and beta chains on 12 cases of classic HCL, as well as on 3 variant cases. The results obtained show that, while the alpha chain of the IL-2 receptor is present only on classic HCL, the IL-2 receptor beta chain (p75) is expressed on both the classic and variant form. Unlike hairy cells, only 8 of the 15 B-cell chronic lymphocytic leukemia cases tested showed a weak expression of the p75 antigen on a small proportion of cells. Purified B lymphocytes from normal healthy controls, as well as Epstein-Barr virus-transformed lymphoblastoid cell lines, showed a weak staining for the p75 determinant, while being CD25-. The results of this study suggest that the expression of the alpha and beta chains of the IL-2 receptor appears to be upregulated or downregulated during the process of B-cell-lineage activation and differentiation.

Cytogenetic rearrangement of C-MYC oncogene occurs prior to infection with Epstein-Barr virus in the monoclonal malignant B cells from an AIDS patient.

Two cell lines were originated from the peripheral blood (PB-LAM) and bone-marrow (BM-LAM) of a patient with Burkitt-type acute lymphoblastic leukemia and AIDS. 26 and 7 clones were isolated from PB-LAM and BM-LAM respectively by limiting dilution. All of these had surface IgM lambda and the CD10 marker with low to absent CD23, CD30, CD39 and surface adhesion molecules. Furthermore, they shared the same chromosomal abnormalities (trisomy 7 and t(8;14) translocation) and the same rearrangements of immunoglobulin L and H chain and of c-myc gene loci. These features are those most frequently found in Burkitt's lymphoma (BL) cells and were different from those of the parental cell lines, which, besides cells identical to those of the malignant clones, also contained normal lymphoblastoid cells. Therefore, the cloning procedure used selected for the growth of cells with malignant features. EBV latent antigens were detected in all clones by Western blotting and their pattern of expression resembled that usually observed in BL cells. All the clones were positive for the EBV genome by Southern blotting and had monomorphic EBV-fused termini as determined by using cDNA probes specific for sequences at either end of the viral genome. However, the clones derived from PB-LAM had EBV fused termini of a different size from that of the clones derived from BM-LAM. The presence of different EBV-fused termini in otherwise monoclonal malignant cells indicate that EBV infection was possibly a late event in lymphomagenesis following rearrangement of the c-myc and the Ig gene loci.

Cyclic neutropenia and severe hypogammaglobulinemia in a patient with excess of CD8-positive T lymphocytes: response to G-CSF therapy.

Cyclic neutropenia is a rare hematological disorder characterized by periodical severe granulocytopenia. A stem cell defect and/or immunological abnormalities are considered to play a role in this disease. Here we describe the case of an adult woman who was diagnosed as having both cyclic neutropenia and severe hypogammaglobulinemia. Her clinical history revealed that one or both abnormalities had been present since childhood. Normal in vitro growth of the patient's bone marrow CFU-GM was observed, while immunological analysis revealed the presence of a persistent excess of activated (HLA-DR+) CD8+ T lymphocytes in both bone marrow and peripheral blood. These T lymphocytes have been shown to be polyclonal by DNA analysis, and their role in determining the clinical picture of our patient remain uncertain since they could not be shown to produce inhibitors of in vitro CFU-GM growth. Intermittent low doses of human recombinant G-CSF were able to improve neutropenia and completely prevent infectious symptoms, thus confirming the efficacy of this cytokine in cyclic neutropenia patients.

Heterogeneous immunophenotype of granular lymphocyte expansions: differential expression of the CD8 alpha and CD8 beta chains.

In this study, we have evaluated 14 large granular lymphocyte (LGL) expansions, 11 of which were CD8+. Analysis of the membrane expression of the alpha and beta chains of the CD8 antigen, using specific monoclonal antibodies (MoAbs), has shown that LGL expansions with the CD3+, CD4+, CD8+, CD57+ T-cell receptor (TcR) alpha beta phenotype bear the CD8 alpha/alpha isoform, while the CD3+, CD4-, CD8+, CD57+ TcR alpha beta samples were positive for both the CD8 alpha and CD8 beta chains. These data were confirmed also by messenger RNA analysis. One additional case, with a peculiar phenotype (CD3-, CD2-, CD4-, CD8+, CD57-) and a germline configuration of the TcR beta and gamma chain genes, expressed only the CD8 alpha chain. After additional phenotypic analysis with a wider panel of MoAbs, it was found that the beta chain of the interleukin-2 receptor was constitutively expressed on the majority of the samples tested, and that most of the monoclonal samples coexpressed CD45RA/R0 antigens. Using MoAbs directed against the variable regions of the TcR beta chain, we could show a preferential V beta region restriction in the CD8+ monoclonal cases. This more extensive characterization of CD8+ LGL expansions has further documented the marked heterogeneity within this rare condition and allowed a better phenotypic dissection between the monoclonal and polyclonal cases.

Unique genotypic features of infant acute lymphoblastic leukaemia at presentation and at relapse.

Acute lymphoblastic leukaemia (ALL) of infants aged less than 1 year represents a group of patients with peculiar biological features, poor response to therapy and unfavourable prognosis. In order better to characterize this type of leukaemia, we have investigated the immunoglobulin (Ig) and T-cell receptor (TCR) genes configuration of 21 infants with ALL, and compared the genotypic features with the phenotypic and karyotypic data, as well as with the clinical outcome. All cases had a pre-B phenotype; 12 (57%) of them were pre-pre-B ALL (CD10-, CD19+). Six of the 16 cases evaluated (38%) displayed chromosomal abnormalities; five had the typical translocation t(4;11)(q21;23). Eleven cases presented with a white blood cell count greater than 100 x 10(9)/l. The clinical course was unfavourable in 14 patients. The genotype of this group of ALL revealed several peculiarities. (1) Of the 21 cases, six (29%) displayed a multiple rearrangement pattern at the IgH locus. (2) In three cases (15%), the light chain genes were rearranged. (3) The TCR beta and gamma genes were rearranged in only one case (one case at the TCR beta and one at the TCR gamma locus). (4) The TCR delta chain was rearranged in eight cases (40%) and rarely deleted; the rearrangements observed were those most frequently observed in B cell-precursor ALL. Two cases were evaluated both at presentation and at relapse. While the immunophenotype had remained unmodified, comparison of Ig heavy chain gene rearrangements revealed clonal variations in both cases. Taken together, these findings further underline the biological peculiarities of infant ALL compared to ALL which occurs in older children and in adults, and stress the need of differentiated and aggressive therapeutic approach for these patients.

Characterization of EBV-positive lymphoblastoid cell lines obtained from HIV seropositive patients with or without lymphomas.

Epstein-Barr-virus- (EBV-) positive lymphoblastoid cell lines (LCLs) spontaneously arising in vitro were obtained from the peripheral blood of six HIV-seropositive patients and from the peripheral blood and the bone marrow of one patient (LAM) with AIDS and lymphoma. The LCLs from HIV-seropositive patients had phenotypic, cytogenetic, and biological characteristics indistinguishable from those of normal LCLs obtained by infecting B cells with EBV in vitro. The LCLs from LAM patient comprised composite cell populations. Cloning analysis and cell fractionation procedures showed that, beside normal EBV-infected cells, these lines contained a malignant subset population characterized by c-myc rearrangement, abnormal karyotype, and a surface phenotype similar to that of Burkitt's lymphoma cells. Analyses of Ig heavy chain and c-myc oncogene loci showed that these malignant cells were the progeny of a single precursor. Nevertheless, these cells had heterogeneous EBV-fused termini, a finding which indicates that EBV infection followed c-myc rearrangement.

Clonally expanded CD3+, CD4-, CD8- cells bearing the alpha/beta or the gamma/delta T-cell receptor in patients with the lymphoproliferative disease of granular lymphocytes.

Among 60 retrospectively assessed patients with the lymphoproliferative disease of granular lymphocytes (LDGL), lymphocytes from only 2 patients had the CD3+, CD4-, CD8- phenotype, rarely observed in normal peripheral blood lymphocytes (about 3%). In this paper we report a detailed study of lymphocytes isolated from these two patients. The cells from patients 1 had the CD3+, CD4-, CD8-, WT31-, beta F1-, TCR delta 1+, Ti gamma A-, BB3+, CD7+, CD16-, CD57+ phenotype, while cells from patient 2 had a phenotype even more rarely observed on normal lymphocytes: CD3+, CD4-, CD8-, WT31+, beta F1+, TCR delta 1-, CD7+, CD16-, CD57+. Thus, in only the first case the cells expressed the gamma/delta T-cell receptor (TCR) on the membrane, while the cells from the second case had the alpha/beta TCR. Genetic studies showed that in case 1 the TCR gamma gene was rearranged and the beta chain gene configuration was germline; the TCR mRNA was of normal size for the gamma chain, while that of the beta chain was truncated. Case 2 had the beta and the gamma genes of the TCR rearranged, but only the alpha and beta mRNA were expressed. In agreement with these findings, the delta chain gene of the TCR was rearranged in case 1 and was deleted in case 2. Cytotoxic activity was absent in cells from case 1 and low in case 2; in the latter, the lytic activity could be up-regulated following incubation with IL-2 or an anti-CD3 monoclonal antibody. Our study indicates that CD3+, CD4-, CD8- lymphocytes are rarely expanded in patients with LDGL. The detection of a lymphoproliferative disease of a CD3+, CD4-, CD8-, alpha/beta + cell may contribute to a better characterization of this novel lymphocytic subpopulation.

Emergence of a B-cell lymphoblastic lymphoma in a patient with B-cell chronic lymphocytic leukemia: evidence for the single-cell origin of the two tumors.

A patient is described who presented with a chronic lymphocytic leukemia (CLL) and later developed a lymphoblastic lymphoma. The cells from the CLL were typical mature B lymphocytes as could be assessed by morphologic, cytochemical, and surface marker analyses. The cells from the lymphoblastic lymphoma were immature B cells that expressed CD10, CD20, and HLA-DR markers, but not surface Ig or cytoplasmic mu chains, and were negative for terminal deoxynucleotidyl transferase (TdT). The cells of two continuous cell lines, obtained from the bone marrow and the peripheral blood of the patient, had the same phenotype as the lymphoblastic lymphoma cells, did not contain the Epstein-Barr virus genome, and displayed malignant features in vitro, including the capacity to form colonies in agar. The two cell lines also shared identical chromosomal abnormalities, a finding which suggests that they derived from the same malignant cell already present in vivo. Such chromosomal abnormalities were not seen in the karyotype of the peripheral blood cells at the onset of the disease. Analysis of the Ig heavy chain genes using a DJ-specific probe showed the very same monoclonal rearrangement in the cells from the B-CLL, the lymphoblastic lymphoma and the two cell lines, thus demonstrating their common clonal origin. By contrast, a monoclonal rearrangement of the lambda chain gene locus was found in the B-CLL cells only, a finding consistent with their exclusive capacity to express surface IgM lambda. This patient represents a rare case in whom a chronic lymphoproliferative disorder with mature malignant cells transforms into a lymphoblastic lymphoma characterized by cells frozen at a very early maturational stage. The possible mechanisms leading to such transformation within the same cell clone are discussed.