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Inadequate molecular and clinical stratification of the patients with high-risk diffuse large B-cell lymphoma (DLBCL) is a clinical challenge hampering the establishment of personalized therapeutic options. We studied the translational significance of liquid biopsy in a uniformly treated trial cohort. Pretreatment circulating tumor DNA (ctDNA) revealed hidden clinical and biological heterogeneity, and high ctDNA burden determined increased risk of relapse and death independently of conventional risk factors. Genomic dissection of pretreatment ctDNA revealed translationally relevant phenotypic, molecular, and prognostic information that extended beyond diagnostic tissue biopsies. During therapy, chemorefractory lymphomas exhibited diverging ctDNA kinetics, whereas end-of-therapy negativity for minimal residual disease (MRD) characterized cured patients and resolved clinical enigmas, including false residual PET positivity. Furthermore, we discovered fragmentation disparities in the cell-free DNA that characterize lymphoma-derived ctDNA and, as a proof-of-concept for their clinical application, used machine learning to show that end-of-therapy fragmentation patterns predict outcome. Altogether, we have discovered novel molecular determinants in the liquid biopsy that can noninvasively guide treatment decisions., (© 2022 by The American Society of Hematology.)

The intercellular crosstalk between hematological malignancies and the tumor microenvironment is mediated by cell-to-cell interactions and soluble factors. One component of the secretome that is gaining increasing attention is the extracellular vesicles and, in particular, the exosomes. Apart from the role as vectors of molecular information, exosomes have been shown to possess intrinsic biological activity. In this study, we found that caspase-3 is activated in L88 bone marrow stroma cell-derived exosomes and identified 1 of the substrates to be the antiapoptotic protein Bcl-xL. The cleaved Bcl-xL is found in a panel of normal and cancer cell-derived exosomes and is localized on the outer leaflet of the exosomal membrane. Incubation of the exosomes with a caspase-3 inhibitor or the pan-caspase inhibitor prevents the cleavage of Bcl-xL. Importantly, MCF-7 cell-derived exosomes that are caspase-3-deficient are enriched in full-length Bcl-xL, whereas ectopic expression of caspase-3 restores the cleavage of Bcl-xL. Chemical inhibition of Bcl-xL with ABT737 or molecular inhibition by using the D61A and D76A Bcl-xL mutant leads to a significant decrease in the uptake of exosomes by hematopoietic malignant cells. These data indicate that the cleaved Bcl-xL is required for the uptake of exosomes by myeloma and lymphoma cells, leading to their increased proliferation. In summary, we demonstrate for the first time that Bcl-xL is an exosomal caspase-3 substrate and that this processing is required for the uptake of exosomes by recipient cells., (© 2016 by The American Society of Hematology.)

Clinical management guidelines on malignant disorders are generally based on data from clinical trials with selected patient cohorts. In Sweden, more than 95% of all patients diagnosed with chronic myeloid leukemia (CML) are reported to the national CML registry, providing unique possibilities to compile population-based information. This report is based on registry data from 2002 to 2010, when a total of 779 patients (425 men, 354 women; median age, 60 years) were diagnosed with CML (93% chronic, 5% accelerated, and 2% blastic phase) corresponding to an annual incidence of 0.9/100,000. In 2002, approximately half of the patients received a tyrosine kinase inhibitor as initial therapy, a proportion that increased to 94% for younger (<70 years) and 79% for older (>80 years) patients during 2007-2009. With a median follow-up of 61 months, the relative survival at 5 years was close to 1.0 for patients younger than 60 years and 0.9 for those aged 60 to 80 years, but only 0.6 for those older than 80 years. At 12 months, 3% had progressed to accelerated or blastic phase. Sokal, but not European Treatment and Outcome Study, high-risk scores were significantly linked to inferior overall and relative survival. Patients living in university vs nonuniversity catchment areas more often received tyrosine kinase inhibitors up front but showed comparable survival.

In recent decades, attention has focused on reducing long-term, treatment-related morbidity and mortality in Hodgkin lymphoma (HL). In the present study, we looked for trends in relative survival for all patients diagnosed with HL in Sweden from 1973-2009 (N = 6949; 3985 men and 2964 women; median age, 45 years) and followed up for death until the end of 2010. Patients were categorized into 6 age groups and 5 calendar periods (1973-1979, 1980-1986, 1987-1994, 1994-2000, and 2001-2009). Relative survival improved in all age groups, with the greatest improvement in patients 51-65 years of age (P < .0005). A plateau in relative survival was observed in patients below 65 years of age during the last calendar period, suggesting a reduced long-term, treatment-related mortality. The 10-year relative survival for patients diagnosed in 2000-2009 was 0.95, 0.96, 0.93, 0.80, and 0.44 for the age groups 0-18, 19-35, 36-50, 51-65, and 66-80, respectively. Therefore, despite progress, age at diagnosis remains an important prognostic factor (P < .0005). Advances in therapy for patients with limited and advanced-stage HL have contributed to an increasing cure rate. In addition, our findings support that long-term mortality of HL therapy has decreased. Elderly HL patients still do poorly, and targeted treatment options associated with fewer side effects will advance the clinical HL field.

The associations between immune-related conditions and multiple myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS) have previously been investigated with inconsistent results. In a large population-based study, we identified 19 112 patients with MM, 5403 patients with MGUS, 96 617 matched control subjects, and 262 931 first-degree relatives. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) for the association of MM and MGUS with immune-related conditions by use of logistic regression. A personal history of all infections combined was associated with a significantly increased risk of MM (OR = 1.2; 95% CI, 1.1-1.3), and a personal history of all conditions in the categories infections (OR = 1.6; 95% CI, 1.5-1.7), inflammatory conditions (OR = 1.4; 95% CI, 1.2-1.5), and autoimmune diseases (OR = 2.1; 95% CI, 1.9-2.4) was associated with a significantly increased risk of MGUS. Several specific immune-related conditions elevated the risk of MM and/or MGUS. A family history of autoimmune disease was associated with a significantly increased risk of MGUS (OR = 1.1; 95% CI, 1.00-1.2), but not MM. Our findings suggest that immune-related conditions and/or their treatment are of importance in the etiology of MGUS and possibly MM. The association of both personal and family history of autoimmune disease with MGUS indicates the potential for shared susceptibility for these conditions.

There is evidence that certain infections and autoimmunity predispose to the development of non-Hodgkin lymphomas (NHLs). A previous study reported that hospitalization for infections in infancy led to an increased risk of NHL. By using population-based registries in Sweden, we compared the rate of hospitalization for infections in infancy between lymphoma cases and matched controls for patients born since 1964. A history of infection was associated with a significantly increased risk of aggressive B-cell lymphomas (odds ratio 2.1, 95% confidence interval 1.11-4.04, P = .02). The specific infections involved were respiratory and intestinal. No effects were observed among cases of Hodgkin lymphoma. This association could result from the infection, its treatment, or could be a surrogate marker for underlying immune defects. Further studies are needed to determine whether this association is present among NHL occurring in older adults and if improved survival of patients with immune defects has contributed to the secular increases in incidence of NHLs.

Patients with multiple myeloma (MM) have an increased risk of fractures. On the basis of small numbers, patients with monoclonal gammopathy of undetermined significance (MGUS) have been reported to have an increased fracture risk. Using population-based data from Sweden, we assessed the risks of fractures in 5326 MGUS patients diagnosed from 1958 to 2006, compared with 20 161 matched controls. MGUS patients had an increased risk of any fracture at 5 (hazard ratio [HR] = 1.74; 95% confidence interval [CI], 1.58-1.92) and 10 (HR = 1.61; 95% CI, 1.49-1.74) years. The risk was significantly higher for axial (skull, vertebral/pelvis, and sternum/costae) compared with distal (arm and leg) fractures (P < .001). On the basis of 10 years of follow-up, there was an increased risk of vertebral/pelvic (HR = 2.37; 95% CI, 2.02-2.78), sternal/costae (HR = 1.93; 95% CI, 1.5-2.48), arm (HR = 1.23; 95% CI, 1.06-1.43), leg (HR = 1.40; 95% CI, 1.26-1.56), and other/multiple fractures (HR = 4.25; 95% CI, 3.29-5.51). Risks for fractures did not differ by isotype or M protein concentration at diagnosis. MGUS patients with (versus without) fractures had no excess risk of MM or Waldenström macroglobulinemia. Our results suggest that bone alterations are present in early myelomagenesis. Our findings may have implications for the development of better prophylaxis for bone disease in MGUS, and they provide novel clues on pathogenesis of MM bone disease.

Patients with multiple myeloma (MM) have an increased risk of venous thrombosis. Interestingly, excess risk of venous thromboembolism has been observed among patients with monoclonal gammopathy of undetermined significance (MGUS). Using population-based data from Sweden, we assessed the risks of venous and arterial thrombosis in 18,627 MM and 5326 MGUS patients diagnosed from 1958 to 2006, compared with 70,991 and 20,161 matched controls, respectively. At 1, 5, and 10 years after MM diagnosis, there was an increased risk of venous thrombosis: hazard ratios (95% confidence intervals) were 7.5 (6.4-8.9), 4.6 (4.1-5.1), and 4.1 (3.8-4.5), respectively. The corresponding results for arterial thrombosis were 1.9 (1.8-2.1), 1.5 (1.4-1.6), and 1.5 (1.4-1.5). At 1, 5, and 10 years after MGUS diagnosis, hazard ratios were 3.4 (2.5-4.6), 2.1 (1.7-2.5), and 2.1 (1.8-2.4) for venous thrombosis. The corresponding risks for arterial thrombosis were 1.7 (1.5-1.9), 1.3 (1.2-1.4), and 1.3 (1.3-1.4). IgG/IgA (but not IgM) MGUS patients had increased risks for venous and arterial thrombosis. Risks for thrombosis did not vary by M-protein concentration (> 10.0 g/L or < 10.0 g/L) at diagnosis. MGUS patients with (vs without) thrombosis had no excess risk of MM or Waldenström macroglobulinemia. Our findings are of relevance for future studies and for improvement of thrombosis prophylaxis strategies.

We evaluated survival patterns for all registered acute myeloid leukemia (AML) patients diagnosed in Sweden in 1973 to 2005 (N = 9729; median age, 69 years). Patients were categorized into 6 age groups and 4 calendar periods (1973-1980, 1981-1988, 1989-1996, and 1997-2005). Relative survival ratios were computed as measures of patient survival. One-year survival improved over time in all age groups, whereas 5- and 10-year survival improved in all age groups, except for patients 80+ years. The 5-year relative survival ratios in the last calendar period were 0.65, 0.58, 0.36, 0.15, 0.05, and 0.01 for the age groups 0 to 18, 19 to 40, 41 to 60, 61 to 70, 71 to 80, and 80+ years, respectively. Intensified chemotherapy, a continuous improvement in supportive care, and allogeneic stem cell transplantation are probably the most important factors contributing to this finding. In contrast, there was no improvement in survival in AML patients with a prior diagnosis of a myelodysplastic syndrome during 1993 to 2005 (n = 219). In conclusion, AML survival has improved during the last decades. However, the majority of AML patients die of their disease and age remains an important predictor of prognosis. New effective agents with a more favorable toxicity profile are needed to improve survival, particularly in the elderly.

Patients with multiple myeloma (MM) have an increased risk of deep venous thrombosis (DVT), particularly when treated with immunomodulatory drugs. Recently, 2 small hospital-based studies observed persons with the MM precursor condition, monoclonal gammopathy of undetermined significance (MGUS), to be at increased risk of developing DVT. Among 4 196 197 veterans hospitalized at least once at US Veterans Affairs hospitals, we identified a total of 2374 cases of MGUS, and 39 272 persons were diagnosed with DVT (crude incidence 0.9 per 1000 person-years). A total of 31 and 151 DVTs occurred among MGUS and MM patients, respectively (crude incidence 3.1 and 8.7 per 1000 person-years, respectively; P < .01). Compared with the entire study population, the relative risk (RR) of DVT after a diagnosis of MGUS and MM was 3.3 (95% confidence interval [CI], 2.3-4.7) and 9.2 (95% CI, 7.9-10.8), respectively. The most prominent excess risk of DVT was found during the first year after diagnosis of MGUS (RR = 8.4; 95% CI, 5.7-12.2) and MM (RR = 11.6; 95% CI, 9.2-14.5). Among 229 MGUS cases (9.5%) that progressed to MM, only one person had a DVT diagnosis before transformation. Our findings suggest the operation of shared underlying mechanisms causing coagulation abnormalities among patients with MGUS and MM.

A role for genetic factors in the etiology of lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) is implicated based on prior findings from multiply affected families and small case-control and cohort studies. We identified 2144 LPL/WM patients (1539 WM [72%] and 605 LPL [28%]) diagnosed in Sweden, 8279 population-based matched controls, and linkable first-degree relatives of patients (n = 6177) and controls (n = 24 609). Using a marginal survival model, we calculated relative risks and 95% confidence intervals as measures of familial aggregation. We found first-degree relatives of LPL/WM patients to have 20-fold (4.1-98.4), 3.0-fold (2.0-4.4), 3.4-fold (1.7-6.6), and 5.0-fold (1.3-18.9) increased risks of developing LPL/WM, non-Hodgkin lymphoma (NHL), chronic lymphocytic leukemia (CLL), and monoclonal gammopathy of undetermined significance (MGUS), respectively. However, there was no evidence of an increased risk of developing multiple myeloma or Hodgkin lymphoma. In analyses stratified by type of first-degree relative (parent, sibling, offspring), age at diagnosis of the probands (greater or less than 70 years), and sex of the first-degree relative, we did not observe the risk estimates to be significantly different compared with the overall analyses. Our findings of highly increased risks of developing LPL/WM, NHL, CLL, and MGUS support the operation of shared susceptibility genes that predispose to LPL/WM and other lymphoproliferative disorders.

Previous small studies have reported familial clustering of myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF). We identified 6217 PV, 2838 ET, 1172 MF, and 812 MPN unclassifiable (NOS) patients diagnosed in Sweden, 43 550 controls, and first-degree relatives of cases (n = 24 577) and controls (n = 99 542). Using a marginal survival model, we calculated relative risks (RRs) and 95% confidence intervals as measures of familial aggregation. Relatives of MPN patients had significantly increased risks of PV (RR = 5.7; 3.5-9.1), ET (RR = 7.4; 3.7-14.8), and MPN NOS (RR = 7.5; 2.7-20.8). Analyses stratified by type of first-degree relative revealed consistently higher risks for siblings, compatible with a model of recessive genetic inheritance, which can be confirmed only by identifying the susceptibility gene(s). Mean age at MPN diagnosis was not different (P = .20) for affected relatives of cases (57.5 years) versus controls (60.6 years), and risk of MPN by age was not different for parents versus offspring of MPN cases (P = .10), providing no support for anticipation. Relatives of MPN patients had a borderline increased risk of chronic myeloid leukemia (CML; RR = 1.9; 0.9-3.8; P = .09). Our findings of 5- to 7-fold elevated risk of MPNs among first-degree relatives of MPN patients support the hypothesis that common, strong, shared susceptibility genes predispose to PV, ET, MF, and possibly CML.

Substantial research has been dedicated to the study of the relationship between genetic mechanisms regulating cell functions in tumors and how those tumors respond to various treatment regimens. Because these mechanisms are still not well understood, we have chosen to study the genetic makeup of 57 tumor samples from patients with follicular lymphoma (FL). Our goal was to develop a prognostic tool, which can be used as an aid in determining FL patients with tumors genetically predisposed to a successful treatment with the CHOP (cyclophosphamide, vincristine, doxorubicin, prednisone) regimen. To select relevant genes, high-density oligonucleotide arrays were used. There were 14 genes highly expressed in FL patients that responded well to CHOP chemotherapy, and 11 of these were involved in G2/M transition of the cell cycle, in mitosis, or in DNA modulation. A high expression of CCNB1 (cyclin B1), CDC2, CDKN3A, CKS1B, ANP32E, and KIAA0101, but not of the proliferation-related antigen Ki-67, was associated with better survival rate in a univariate analysis. CCNB1 expression had an independent prognostic value when included in a multivariate analysis together with the 5 parameters of the follicular lymphoma international prognostic index.

Biosynthesis of leukotrienes (LTs) occurs in human myeloid cells and B lymphocytes. However, the function of leukotrienes in B lymphocytes is unclear. Here, we report that B-cell chronic lymphocytic leukemia (B-CLL) cells produce leukotriene B(4), and that specific leukotriene biosynthesis inhibitors counteracted CD40-dependent activation of B-CLL cells. Studies on the expression of the high-affinity receptor for LTB(4) (BLT1) by flow cytometry analysis showed that the receptor was expressed, to a varying degree, in all investigated B-CLL clones. At a concentration of 100 nM, the drugs BWA4C (a specific 5-lipoxygenase inhibitor) and MK-886 (a specific 5-lipoxygenase activating protein inhibitor) markedly inhibited CD40-induced DNA synthesis (45% and 38%, respectively) and CD40-induced expression of CD23, CD54, and CD150. Addition of exogenous LTB(4) (150 nM) almost completely reversed the effect of the inhibitors on DNA synthesis and antigen expression. Taken together, the results of the present study suggest that leukotriene biosynthesis inhibitors may have a therapeutic role in B-CLL.

This study was designed to test the hypothesis that administration of granulocyte colony-stimulating factor (G-CSF; filgrastim) during induction chemotherapy with CHOP (cyclophosphamide, vincristine, doxorubicin, prednisone) or CNOP (doxorubicin replaced with mitoxantrone) in elderly patients with aggressive non-Hodgkin lymphoma (NHL) improves time to treatment failure (TTF), complete remission (CR) rate, and overall survival (OS). Furthermore, the efficacy of CHOP versus CNOP chemotherapy was compared. A total of 455 previously untreated patients older than 60 years with stages II to IV aggressive NHL were included in the analysis. Patients (median age, 71 years; range, 60-86 years) were randomized to receive CHOP (doxorubicin 50 mg/m(2)) or CNOP (mitoxantrone 10 mg/m(2)) with or without G-CSF (5 microg/kg from day 2 until day 10-14 of each cycle every 3 weeks; 8 cycles). Forty-seven patients previously hospitalized for class I to II congestive heart failure were randomized to receive CNOP with or without G-CSF (not included in the CHOP versus CNOP analysis). The CR rates in the CHOP/CNOP plus G-CSF and CHOP/CNOP groups were the same, 52%, and in the CHOP with or without G-CSF and CNOP with or without G-CSF groups, 60% and 43% (P <.001), respectively. No benefit of G-CSF in terms of TTF and OS could be shown (P =.96 and P =.22, respectively), whereas CHOP was superior to CNOP (TTF/OS P <.001). The incidences of severe granulocytopenia (World Health Organization grade IV) and granulocytopenic infections were higher in patients not receiving G-CSF. The cumulative proportion of patients receiving 90% or more of allocated chemotherapy was higher (P <.05) in patients receiving G-CSF. Concomitant G-CSF treatment did not improve CR rate, TTF, or OS. Patients receiving CHOP fared better than those given CNOP chemotherapy. The addition of G-CSF reduces the incidence of severe granulocytopenia and infections in elderly patients with aggressive NHL receiving CHOP or CNOP chemotherapy.

This phase II study determined the efficacy and safety of alemtuzumab, a humanized anti-CD52 monoclonal antibody, delivered subcutaneously as first-line therapy, over a prolonged treatment period of 18 weeks in 41 patients with symptomatic B-cell chronic lymphocytic leukemia (B-CLL). Injections were administered subcutaneously 3 times per week, from week 2 to 3 onward. An overall response rate (OR) of 87% (95% CI, 76%-98%; complete remission [CR], 19%; partial remission [PR], 68%) was achieved in 38 evaluable patients (81% of intent-to-treat population). CLL cells were cleared from blood in 95% patients in a median time of 21 days. CR or nodular PR in the bone marrow was achieved in 66% of the patients and most patients achieved this after 18 weeks of treatment. An 87% OR (29% CR) was achieved in the lymph nodes. The median time to treatment failure has not yet been reached (18+ months; range, 8-44+ months). Transient injection site skin reactions were seen in 90% of patients. Rigor, rash, nausea, dyspnea, and hypotension were rare or absent. Transient grade IV neutropenia developed in 21% of the patients. Infections were rare, but 10% patients developed cytomegalovirus (CMV) reactivation. These patients rapidly responded to intravenous ganciclovir. One patient, allergic to cotrimoxazole prophylaxis, developed Pneumocystis carinii pneumonia. Alemtuzumab is highly effective as first-line treatment in patients with B-CLL. Prolonged treatment is important for maximal bone marrow response. Subcutaneous administration induced very few "first-dose" flulike symptoms and may reduce health care costs in comparison with the intravenous infusions.

Using Western blot analysis, we examined cyclin E and cyclin A protein levels in 19 patients with acute lymphoblastic leukemia ([ALL] 15 B-ALL and four T-ALL). Whereas normal, nonproliferating peripheral blood mononuclear cells (PBMCs) expressed low levels of the 50-kD cyclin E, ALL blasts in the peripheral blood, although showing low-level or no proliferation as judged by FACS/cell-cycle analysis and cyclin A protein levels, expressed high levels of cyclin E, with a mean value similar to that of the proliferating Burkitt's lymphoma cell line, Akata. The accumulation of a protein shown to shorten the G1 phase of the cell cycle, cyclin E, in growth-delayed leukemic blasts may reflect the malignant status of these cells. Before treatment, B-ALL cells expressed predominantly the 50-kD cyclin E. T-ALL samples displayed the 50-kD cyclin E protein and a smaller, approximately 43-kD cyclin E species. In paired B-ALL samples taken before treatment and at relapse, we found a significant overexpression of the 50-kD protein in relapsed samples (P < .006), plus the presence of up to four additional smaller-molecular-weight species of cyclin E, illustrating clear diagnosis versus relapse differences. Cyclin E expression in ALL blasts may correlate to the relative malignant status of the cells, with higher protein levels reflecting a more advanced stage of the disease and a greater potential to proliferate under permissive conditions.

Three hundred thirty-five previously untreated patients with multiple myeloma in clinical stages II and III entered a randomized trial comparing intermittent oral melphalan and prednisone (MP) therapy (n = 171) with MP in combination with natural (leukocyte-derived) alpha-interferon (MP/IFN) (n = 164). The treatment groups were comparable with regard to major prognostic factors. The response frequency was 42% in the MP group and 68% in the MP/IFN group (P < .0001). Eighty-five percent of IgA myelomas and 71% of Bence-Jones myelomas responded to MP/IFN compared with 48% and 27%, respectively, to MP treatment (P = .001). There was no difference in the overall survival between the two treatment groups. However, the survival of 72 patients with IgA or Bence-Jones myeloma randomized to receive MP/IFN was significantly longer (median 32 months) than that of 71 patients treated with MP (median 17 months) (p < .05). No statistically significant difference in response frequency (60% v 46%) or survival was found for patients with IgG myeloma. Hematologic toxicity, WHO grades III and IV, was higher in the MP/IFN group (48%) than in the MP group (33%) (P < .05) during the induction treatment period. Flulike syndrome was observed in 68% of patients receiving MP/IFN. The results show that MP/IFN is a well-tolerated treatment regimen, superior to MP for remission induction, and it improves significantly the overall survival for patients with IgA and Bence-Jones myelomas.

Untreated patients with Hodgkin's disease (HD) have a blood T-lymphocytopenia mainly caused by a reduction of the CD4+ subset. Indirect support for a sequestration of T cells in the spleen and tumor-involved lymphoid tissue has accumulated. To test the hypothesis that the blood CD4 T-lymphocytopenia in patients with HD is caused by an altered lymphocyte traffic, 12 untreated HD patients and five in complete clinical remission (CCR) were studied. Blood lymphocytes were collected by leukapheresis and gradient centrifugation, and were further purified by an adherence step. The cells were labeled with indium-111 oxine and reinfused intravenously into the patient. The radioactivity of CD4+ and CD8+ blood lymphocytes separated by immunoabsorption was measured from serial blood samples. CD4+ cells were eliminated more rapidly in untreated patients than patients in CCR. Repeated gamma camera imaging after autotransfusion of indium-111 oxine labeled cells demonstrated an accumulation of radioactivity in tumor-involved tissue of untreated patients. These findings support the concept of an enhanced elimination of CD4+ cells in patients with active HD that may contribute to the observed blood T-lymphocytopenia and may reflect a biologic response to the tumor.

Neoplastic populations from 25 cases of B-lymphocytic leukemia (B-LL) were investigated in an attempt to define the stages of maturation arrest represented in this disease and the relationship, if any, to various clinical parameters. Intrinsic to this study was the expression of a number of B-cell antigens defined by monoclonal antibodies. These included antibodies to B1 and B2, both expressed exclusively on B lymphocytes, but with the latter probably restricted to a narrow window of differentiation, BB-1 and LB-1, both markers of activated lymphocytes, and 38.13, a monoclonal antibody raised against and recognizing an epitope expressed on Burkitt lymphoma cells. While the patterns of reactivities were complex, the cases could be classified into various groups on the basis of the phenotypes revealed. These were termed "pre-B," "early-B," "intermediate-B," "mature-B," and "secretory-B" from their patterns of immunoglobulin (Ig) isotype expression and their capacity to secrete Ig in short-term culture. Although B1 was detected on neoplastic cells from all but one case, its intensity of expression varied markedly, being strongest on the "mature-B" and "secretory-B" cases and weakest on the "pre-B" type. The expression of B2 was essentially restricted to the "intermediate-B," "mature-B," and "secretory-B" cases and was usually, but not invariably, accompanied by the coexpression of surface IgM and IgD. While expression of BB-1 was restricted to a few cases with mature features, LB-1 was more frequently detected and found predominantly on "intermediate-B" and "mature-B" cases. The 38.13 antibody was found to react weakly with a number of the populations coexpressing IgM and IgD. The export of large amounts of whole Ig was restricted to three "secretory-B" cases all of which were associated with a serum M-component corresponding to the Ig isotype secreted in vitro. In contrast, the secretion of free Ig light chains was a consistent feature of all B-LL, and the amounts detected did not vary considerably between the different types. No correlation between immunologic cell-type and the stage of the disease was apparent. Classification of the cases into "true" B-chronic lymphocytic leukemia and immunocytoma similarly revealed no strict association of these histopathologic entities with any particular phenotypic group, although those cases with the more mature features tended to be immunocytomas. The findings are discussed within the context of normal B-cell differentiation pathways.