B-cell neoplasms of the lymphocytic, lymphoplasmacytoid, and plasma cell types: immunohistologic analysis and clinical correlation

Histopathological features and immunophenotyping of canine transmural gastrointestinal lymphoma using full-thickness biopsy samples

To elucidate the histopathological characteristics and immunophenotypes of canine transmural "mass-forming" gastrointestinal lymphomas and plasmacytomas, 83 surgically resected biopsy samples were examined. All lymphomas and plasmacytomas were located in the small or large intestine except for 1 plasmacytoma which was in the stomach. According to the World Health Organization (WHO) classification, B-cell neoplasms (17 cases) included lymphoplasmacytic lymphoma (6/17), plasmacytoma (5/17), follicular lymphoma (3/17), and diffuse large B-cell lymphoma (3/17). Based on nuclear sizes, T-cell neoplasms (66 cases) were broadly divided into large cell lymphoma (LCL; 48/66) and small cell lymphoma (SCL; 18/66). According to the WHO classification, T-cell neoplasms included anaplastic large T-cell lymphoma (ALCL; 10/66), angiotropic T-cell lymphoma (3/66), mixed inflammatory type peripheral T-cell lymphoma (mixed inflammatory type PTCL; 33/66), and PTCL-not otherwise specified (PTCL-NOS; 20/66). Mixed inflammatory type PTCLs were further divided into histiocyte- (27/33) and eosinophil- (6/33) dominant types. Immunohistochemically, lymphoplasmacytic lymphomas were positive for Pax5 (6/6) and IgM (5/6), while plasmacytomas were positive for IgG (5/6) and negative for Pax5. LCLs were immunopositive for granzyme B in 31/48 cases (65%) and CD8 in 9/48 cases (19%), while SCLs were immunopositive for granzyme B in 3/18 cases (17%) and CD8 in 3/18 cases (17%). Furthermore, 8/10 cases (80%) of ALCL and 19/27 cases (70%) of histiocyte-dominant PTCL were immunopositive for granzyme B, whereas 6/20 cases (30%) of PTCL-NOS, 1/6 cases (17%) of eosinophil-dominant PTCL, and no cases of angiotropic T-cell lymphomas were immunopositive for granzyme B. The present study describes the immunophenotypes in different histological types of transmural gastrointestinal lymphomas in the dog.

Histologic Transformation in an Untreated Waldenstrom's Macroglobulinemia After 14 Years: Case Report and Review of the Literature

Waldenstrom's macroglobulinemia (WM) is an indolent B-cell non-Hodgkin lymphoma characterized by lymphoplasmacytic histology in the bone marrow with monoclonal IgM. Median survival can be in excess of 10 years. The 5-year cumulative incidence of death is low at about 10%. One-third of all-cause specific mortality is due to the lymphoma for which histologic transformation (HT) is rare. Here we present a case of a 60-year-old man with longstanding untreated WM, presenting with minimally symptomatic transformation to diffuse large B-cell lymphoma (DLBCL), with an accompanying review of the literature. Transformed WM, diagnosed greater than 5 years, has a reported survival period of 8 - 9 months. This case highlights that after a decade of continued stability in WM, not requiring treatment, an acute change in laboratory data with minimally progressive IgM levels, in the absence of B symptoms and clinical findings, may be the harbinger of transformation and at the time of diagnosis can have a rapidly deteriorating clinical course. In this case, the tripling of the lactate dehydrogenase (LDH) as the primary drastic change demonstrates the importance of the rapid increase in LDH as a singly reliable marker for HT. Late transformation has been borne out as a negative variable as the generally indolent course of WM is curtailed with the poor outcome in HT. Although MYD88 wildtype is a possible predictive factor for transformation, it is unclear if late transformation is clonally or non-clonally related and further molecular investigation is needed.

Chronic lymphocytic leukemia/small lymphocytic lymphoma: another neoplasm related to the B-cell follicle?

Although there has been increased attention paid to the critical nature of nodal involvement in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), the B-cell compartment it is most closely related to and its relationship to the follicle remain uncertain. A clinicopathologic investigation of 60 extramedullary biopsies of LEF1+ CLL/SLL, including 29 cases with perifollicular/follicular (PF/F) growth, was therefore performed. A subset of PF/F cases demonstrated inner mantle zone preservation or intra-mantle zone growth. All PF/F and 16/31 other cases contained CD21+ follicular dendritic cells. No cytogenetic, IGHV mutational or gene usage differences were seen between PF/F and diffuse cases. PF/F cases were more often kappa positive (p<0.03) and had fewer involved nodal sites (p=0.0004). These findings suggest that at least a subset of bona fide CLL/SLL is related to the follicle, most likely the outer mantle zone, and that at least a subset of the diffuse cases may represent "later" disease.

Follikuläre Lymphome und Mantelzelllymphome

Indolent (low-grade) B-cell non-Hodgkin's lymphomas, such as follicular and mantle cell lymphomas, are primarily nodal lymphomas in which lymph node involvement is the dominant clinical feature. The frequency of extranodal manifestations of these primarily nodal lymphomas is often underestimated. The typical growth pattern of nodal lymphomas can be absent or not evaluable because the biopsy specimens are often small in cases with extranodal involvement. Therefore, the immunophenotype of the lymphoma cells is of great importance for the diagnosis of indolent lymphomas with extranodal localizations.

Immunohistochemistry in bone marrow pathology: a useful adjunct for morphologic diagnosis

Pathomorphological examination of trephine biopsies of the bone marrow (BM) represents a standard method for the diagnosis and staging of hematologic neoplasms and other disorders involving the BM. The increasing knowledge about the genetic basis and biology of hematologic neoplasms, as well as the recently proposed WHO classification system, provide the framework for an accurate diagnosis. Although conventional morphology remains the gold standard for paraffin-embedded BM trephines, immunohistochemical stainings have become an integral part of the diagnostic workup. Antibodies suitable for paraffin sections are generally applicable to BM trephines, but modifications of staining protocols may be necessary due to the alternative fixatives and decalcification procedures used for BM biopsies. The indications for immunostainings range from confirmation and classification of lymphoma involvement, subclassification of acute leukemias, and estimating blast counts in myelodysplastic and myeloproliferative syndromes to characterization of BM involvement in nonhematologic neoplasms. Although subtyping of NHL in the BM is more difficult from the point of morphology, classification of the entities that frequently involve the BM, especially the small B-cell lymphomas, can easily be achieved with the help of immunohistochemistry. In this review, we try to summarize the current state of the art in BM immunohistochemistry for the diagnosis of hematologic disorders. Moreover, diagnostic algorithms and useful antibody panels are proposed for a rational and cost-effective approach.

Assessment of CD10 in the diagnosis of small B-cell lymphomas: a multiparameter flow cytometric study

We evaluated the usefulness of multiparameter flow cytometry with cluster analysis in the diagnosis of a series of 100 well-characterized small B-cell lymphomas (SBCLs). The histologic diagnoses in the 100 cases were follicular lymphoma (FL) in 58, marginal zone lymphoma (MZL) in 17, small lymphocytic lymphoma in 15, and mantle cell lymphoma (MCL) in 10. Of the 58 FLs, 57 were CD10 positive (98% sensitivity). The 1 negative case was unusual in that it occurred in the small intestine. However; architectural, cytologic, and immunohistochemicalfeatures were diagnostic of FL. Of 42 other SBCLs, 2 were CD10+ (95% specificity); 1 was a CD5+/cyclin D1 + MCL, and the other was an extranodal MZL. We found that assessment of CD10 expression using multiparameter flow cytometry with cluster analysis is highly sensitive and specific for the diagnosis of FL, validating its usefulness in situations in which adequate tissue is not available for definitive histologic diagnosis.

Is lymphoplasmacytic lymphoma/immunocytoma a distinct entity? A clinicopathologic study of 20 cases

Lymphoplasmacytic lymphoma/immunocytoma (LLI) was defined initially as a small B-cell lymphoma with plasmacytoid or plasmacytic features. Because other types of small B-cell lymphoma, particularly marginal zone B-cell lymphoma may exhibit plasmacytic differentiation, the revised European-American lymphoma classification and World Health Organization has defined LLI more narrowly to exclude other small B-cell lymphomas. The goal of this study was to reevaluate LLI as a clinicopathologic entity. Twenty cases were selected from 43 previously diagnosed as "small lymphocytic lymphoma, plasmacytoid" or "immunocytoma" from 1985 to 1998. Cases fulfilling the criteria for B-cell small lymphocytic lymphoma, follicular lymphoma, marginal zone B-cell lymphoma, or other types of B-cell lymphoma were excluded. The histopathology and immunoreactivity for CD20, CD79a, CD3, CD43, CD23, CD5, kappa, lambda, and immunoglobulins (Ig's) M, G, and A were reviewed, in addition to available clinical findings. There were 13 men and seven women, with a mean age of 69 years. Five patients had documented Waldenström's macroglobulinemia (WM). Three architectural patterns were observed. Pattern A (seven of 20) showed open sinuses, small follicles, and hemosiderosis; pattern B (four of 20) showed hyperplastic follicles; and pattern C (nine of 20) showed diffuse effacement. Epithelioid histiocytes were prominent in patterns B and C but absent in A. Cytologically, six of 20 were polymorphous with 10% to 40% transformed cells; 14 of 20 were lymphoplasmacytic. Five cases showed minor foci of monocytoid B cells. One case showed a composite histology of LLI and small lymphocytic lymphoma. Amyloid was present in two cases. All cases were CD20 and/or CD79a immunoreactive, with two of 20 positive for CD43. Twelve cases were kappa monoclonal and eight cases were lambda monoclonal. Twelve of 17 cases that could be evaluated were positive for IgM and five were positive for IgG. All cases were negative for CD5 and CD23 with the exception of the one case with a composite histology. Eleven of 20 patients with available follow-up died of disease (median, 48 months), and eight of 20 are alive with disease at a follow-up of 6 months to 2 years. LLI does appear to represent a distinct clinicopathologic entity even though it shows morphologic heterogeneity and overlapping features with marginal zone B-cell lymphoma and small lymphocytic lymphoma. Recognition of LLI is important because the overall prognosis may be worse than for other types of small B-cell lymphomas.

Splenic marginal zone lymphoma with or without plasmacytic differentiation

We report a series of 31 cases of splenic marginal zone lymphomas with an enlarged spleen and a multimicronodular macroscopic pattern. Two groups, A and B, were distinguished based on the presence (A) or absence (B) of a lymphoplasmacytic component with monoclonal immunoglobulin expression in the cytoplasm. There were no differences between the groups as far as age, sex, spleen weight, and progression. The only difference was the presence in group A of a monoclonal serum component and autoimmune disorders, particularly autoimmune hemolytic anemia. In most cases in which a liver and/or bone marrow biopsy was performed, lymphomatous infiltration was detected. Seven cases had a seric monoclonal IgM of 5 g/L or more and liver or bone marrow infiltration, corresponding to the definition of Waldenstrom's macroglobulinemia. Lymphoma cells had a monocytoid, centrocytoid and, in group A, lymphoplasmacytic morphology. The lymphomatous cells were positive for CD20, CD45 RA, and bcl-2. They expressed IgD in 9 cases, partially in 6, and were negative for IgD in 9 of the 24 cases studied. Progression seems to be slow, with a long survival. Three patients presented with transformation into a large B-cell lymphoma, which was responsible for death in two patients.

Paraffin-section detection of CD10 in 505 nonhematopoietic neoplasms. Frequent expression in renal cell carcinoma and endometrial stromal sarcoma

We tested 505 cases of nonhematopoietic neoplasms by immunohistochemistry using a newly characterized monoclonal antibody (clone 56C6) against the CD10 antigen. CD10 was expressed widely in neoplasms of the genitourinary tract, including 41 (89%) of 46 cases of renal cell carcinoma, 13 (54%) of 24 cases of transitional cell carcinoma, and 11 (61%) of 18 cases of prostatic adenocarcinoma. In addition, 5 (100%) of 5 endometrial stromal sarcomas, 3 (60%) of 5 rhabdomyosarcomas, 7 (50%) of 14 pancreatic adenocarcinomas, 5 (45%) of 11 cases of schwannoma, and 12 (40%) of 30 cases of malignant melanoma also were positive for CD10. Similar to normal tissue, CD10 positivity was restricted to the apical surface of malignant glandular cells of well-differentiated colonic, pancreatic, and prostatic adenocarcinoma, whereas in poorly differentiated adenocarcinoma and other tumors, such as melanoma, transitional cell carcinoma, renal cell carcinoma, and endometrial stromal sarcoma, the CD10 positivity showed diffuse cytoplasmic or membranous/Golgi patterns. The monoclonal antibody clone 56C6 is a reliable marker for CD10 in paraffin immunohistochemistry after heat-induced epitope retrieval. CD10 expression in renal cell carcinoma and endometrial stromal sarcoma may be a useful marker in the differential diagnoses of these tumors because both tumors otherwise lack specific markers.

Multicenter phase II study of fludarabine phosphate for patients with newly diagnosed lymphoplasmacytoid lymphoma, Waldenström's macroglobulinemia, and mantle-cell lymphoma

PURPOSE

Fludarabine phosphate (F-AMP) has significant activity in follicular lymphoma and in B-cell chronic lymphatic leukemia, where it has demonstrated high complete response (CR) rates. Lymphoplasmacytoid (LPC) lymphoma, Waldenstrom's macroglobulinemia (WM), and mantle-cell lymphoma (MCL) also present with advanced-stage disease and are incurable with standard alkylator-based chemotherapy. A phase II trial was undertaken to determine the activity of F-AMP in patients newly diagnosed with these diseases.

PATIENTS AND METHODS

Between 1992 and 1996, 78 patients (aged 18 to 75 years) received intravenous F-AMP (25 mg/m2/d for 5 days, every 4 weeks) until maximum response, plus two further cycles as consolidation. The primary end point was response rate; secondary end points included time to progression (TTP), duration of response, and overall survival (OS).

RESULTS

Forty-four (62%) of 71 assessable patients had a response to F-AMP (LPC lymphoma, 63%; WM, 79%; MCL, 41%); the CR rate was 15%. At a median follow-up of 1.5 years, 19 of 44 responding patients have had progression of lymphoma; the median duration of response was 2.5 years. The median survival has not yet been reached. There was no significant difference in the duration of response or OS between patients with different histologies; TTP was shorter in patients with MCL (P = .015). Myelosuppression was relatively common, and the treatment-related mortality (TRM) was 5%, mostly associated with pancytopenia and infection.

CONCLUSION

Single-agent fludarabine phosphate is active in previously untreated LPC lymphoma and WM, with only moderate activity in MCL. However, the CR rate is low, and the TRM is relatively high. Its role in combination chemotherapy remains to be demonstrated.

Cell proliferation, bcl-2, c-myc, p53 and apoptosis as indicators of different aggressiveness in small lymphocytic lymphoma (SLL)

Cell proliferation activity, by MIB1 mAb, expression of bcl-2, c-myc and p53 gene proteins and apoptotic index (AI) were assessed in 54 cases of SLL and compared to the morphological subtypes of this disorder, defined by Lennert on the basis of amount and distribution of small and larger activated lymphocytes as diffuse, tumor-forming and pseudofollicular subtypes (DS, TFS, PFS). MIB1 scores showed significant differences between DS, PFS and TFS (5.5%, 16.61% and 24.14%, respectively; p < 0.0001). Worth noting, the MIB1 score did not differ significantly when comparing DS with the diffuse areas of PFS, or TFS with the pseudofollicles of PFS. The mean bcl-2 gene protein score was displayed to a high extent in all subtypes, but less extensively by larger activated lymphocytes that, conversely, expressed c-myc. MIB1 score correlated negatively with bcl-2 and positively with c-myc protein scores. These findings suggest that lymphocytes protected from apoptosis by bcl-2 would be exponed to cell activation and growth acceleration provided by c-myc. This condition would account for a different aggressiveness of morphologically activated subtypes, such as TFS and PFS with larger pseudofollicles. The survival analysis, performed in 23 cases, showed a trend of association of cell proliferation and c-myc expression with a more aggressive progression of the disease. Overexpression of p53 and apoptosis were found only in a minority of cases, unrelated to the subtypes. In conclusion, cell growth fraction, bcl-2 and c-myc assessment may be of help in predicting the aggressiveness of different subtypes of SLL. This approach should be most conveniently applied to PFS, which represents a continuum between DS and TFS, in order to distinguish, in this heterogeneous subtype, more indolent from more aggressive disorders.

New classification of low-grade lymphoma

The problem of morphologic classification of the indolent non-Hodgkin's lymphomas has been addressed by the National Cancer Institute Working Formulation, the International Lymphoma Study Group, and other groups. The criteria for classification have expanded to include biologic and laboratory parameters. Clinical aspects are important, because diagnostic categories that obscure discrete entities, such as mucosa-associated B-cell lymphoma could adversely affect therapy. This and other indolent non-Hodgkin's lymphomas and mantle-cell lymphoma, which has been provisionally included among them, are reviewed. Variations in nomenclature, immunohistochemical and molecular characteristics, and whenever possible, prognosis and clinical outcome are described. The need for further correlation with clinical outcome of these entities is noted.

Low-grade lymphomas: new entities and treatment concepts

Therapy for patients with low-grade lymphomas has never been standardized. Recently, new entities have been described which are included in the REAL classification, and whether these entities should be regarded as separate diseases is not yet clear. Regardless, three new developments in the management of patients with low-grade lymphomas deserve special attention for treatment programs in the future. First, it appears that patients with stage I, II, and III low-grade lymphomas may enjoy very prolonged disease-free intervals after treatment with combination chemotherapy and radiation therapy programs. Although investigators disagree on prognostic factors, new features, such as beta 2-microglobulin appear to predict results better than any other feature, and future studies should address this prognostic factor in assessing their results. Second, for patients with advanced stage disease, administration of interferon as maintenance therapy prolongs the disease-free interval, and use of this drug should be further investigated. Finally, molecular studies using PCR for bcl-2 may be clinically relevant in detecting residual disease in patients with follicular lymphomas, and future studies should focus on the value of eliminating the residual disease from blood and marrow.

UCL3D3 and UCL4D12 reactivity in small B-cell neoplasms with special emphasis on monocytoid B-cell lymphoma

Two recently described monoclonal antibodies, UCL3D3 and UCL4D12, have been reported to have some specificity for mantle zone B lymphocytes and marginal zone/follicular center B lymphocytes, respectively, in the spleen. Forty-nine B-cell neoplasms, including 20 cases of monocytoid B-cell lymphoma (MBCL), were studied by frozen section immunohistochemistry with these antibodies to evaluate their utility. Tonsil, lymph node, and reactive spleen also were studied with the antibodies. Although a wide overlap was observed among the different lymphomas, a majority of cases of MBCL and half of cases of hairy cell leukemia (HCL) reacted with both markers, suggesting both marginal/follicular and mantle cell antigen expression. None of four cases of mantle cell lymphoma reacted with the proposed mantle cell marker UCL3D3, whereas three of these cases immunoreacted with UCL4D12. This marker is known to react with a subpopulation of follicular center cells and possibly with marginal zone lymphocytes. A comparison of nodal and extranodal neoplasms failed to show a significant difference in the pattern of immunoreactivity with these antibodies. Tonsil and lymph node controls showed some mantle zone staining with both antibodies, and there was a slight overlap in mantle and marginal zone staining of the spleen controls. These findings suggest an immunologic similarity between some cases of HCL and MBCL. However, the findings also would suggest that these antibodies, particularly UCL4D12, have less specificity than has been previously assumed, and UCL4D12 may not have practical utility in the evaluation of low grade B-cell lymphomas.

Clinicopathologic, enzyme and histochemical studies of centrocytic (mantle cell) lymphoma: comparison with other types of low-grade B cell lymphoma based on the updated Kiel classification

Lymph nodes from 21 cases of malignant lymphoma of a centrocytic (mantle cell) type, (ML, cc (mc)) were examined. All the cases had monoclonal surface immunoglobulin (sig) M and/or D, but were negative for CD10 (CALLA), and CD11c (LeuM5). Lymphoma cells with CD25 (anti-Tac)+, CD5 (Leu1)+, and alkaline phosphatase (ALPase)- in eight cases showed bone marrow involvement (10-66% of the nucleated cells; mean 32 +/- 18%) but with no leukemic changes. These eight cases had a similar phenotype and were distributed by the lymphoma cells to the examined B-chronic lymphocytic leukemia. Seven cases showed an infiltration of CD25-, CD5+, and ALPase- lymphoma cells, in which only two cases showed focal bone marrow involvement. There was a close relationship between CD25 expression and bone marrow invasion by the lymphoma cells in ML, cc (mc). Three of the six CD25- and CD5- cases presented zonal proliferation of ALPase+ lymphoma cells with round nuclei and a high anti-proliferating cell nuclear antigen/cyclin (PCNA/c) rate in the mantle zone and paracortex, accompanied by a prominent interdigitating dendritic and histiocytic cell reaction. Examined CD25-, CD5- and ALPase+ lymphoma showed a neoplastic counterpart of so-called marginal zone lymphocytes, which was different from other cases of ML, cc (mc). Lymphoma cells in ML, cc (mc), except for those of the so-called marginal zone lymphoma, might be derived from slgM+, D+/-, CD25+/-, CD5+/-, ALPase-, CD10- and CD11c- lymphocytes present in the mantle zone and primary lymph follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Discordant LFA-1/ICAM-1 expression in a case of secondary plasma cell leukemia associated with subcutaneous plasmacytoma

We observed a unique case of multiple myeloma that was transformed into plasma cell leukemia presenting with subcutaneous and soft tissue infiltrates. Subcutaneous and minor pelvic soft tissue plasmacytomas and the leukemic transformation were diagnosed in a 72-year-old woman after she had completed 9 months of chemotherapy for IgG kappa multiple myeloma. Immunophenotypic study revealed that leukemic cells in her peripheral blood were positive for ICAM-1 (CD54) but negative for LFA-1 alpha (CD11a) and LFA-1 beta (CD18), whereas infiltrating leukemic cells in the subcutaneous plasmacytoma of the left thigh were positive for LFA-1 alpha and LFA-1 beta but negative for ICAM-1. In addition, intermingling capillary endothelial cells were positive for ICAM-1. Extramedullary soft tissue plasmacytoma is uncommon in association with plasma cell tumors, and the exact mechanism of the development of plasmacytoma is not known. In the present case, however, the discordant expression of LFA-1/ICAM-1 adhesion molecules may have accounted for the distinct patterns of growth and the spread of the subcutaneous plasmacytoma through homing of the LFA-1 alpha+, LFA-1 beta+ leukemic cells to ICAM-1+ endothelial cells.

Immunoglobulin V gene expression in CD5 B-cell malignancies

Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphomas (SLL) generally are malignancies of CD5 B cells. Immunophenotypic and clinicopathologic data, however, are required to distinguish subtypes that apparently have a different cytogenesis than that of conventional CLL or SLL. In addition to expressing CD5, neoplastic cells of the latter are also distinctive in that they frequently coexpress surface immunoglobulin (Ig), bearing one or more cross-reactive idiotypes (CRIs) (e.g. 17.109, G6,) that commonly are found on monoclonal IgM autoantibodies. The frequent occurrence of such CRIs reflects both the biased rearrangement and subsequent selected expression of Ig V genes with little or no somatic mutation. IgM/L CLL, for example, frequently (8/33) harbor abortive Ig rearrangements involving Humkv325, the VK gene encoding the 17.109-CRI. Also, the VH1 gene(s) encoding the G6 CRI accounts for over 10% of all VH genes and over 60% of all the VH1 genes used in randomly selected common CLL/SLL. Furthermore, comparison with the Ig expressed by nonmalignant G6 CRI+ B cells reveals an apparent restriction in the CDR3 of IgH expressed by G6 CRI+ CLL. Coupled with the observed potential bias in antibody light chain and heavy chain pairing in B-CLL, these data suggest that the autoantibodies expressed in this disease are selected based on antigen-binding activity. Collectively, our studies indicate that nonstochastic Ig V gene rearrangement and subsequent selection may influence the Ig repertoire expressed in this common B-cell malignancy.

Primary biphasic lymphoplasmacytic lymphoma of the lung. A mucosa-associated lymphoid tissue lymphoma with compartmentalization of plasma cells in the lung and lymph nodes

A primary mucosa-associated lymphoid tissue lymphoma of the lung in a 27-year-old man was found. The tumor was composed mainly of centrocyte-like cells and plasma cells. These two components were demarcated sharply from each other, resulting in a zoning or biphasic pattern. This characteristic pattern also was present in the involved regional lymph nodes. Monoclonality of tumor cells was shown immunohistochemically and by in situ hybridization techniques. This article also highlights the use of in situ hybridization in detecting light chain mRNA in paraffin sections.

Surface immunoglobulin density in the differential diagnosis of B-cell chronic lymphocytic leukemia and leukemic immunocytoma

Using flow cytometry peripheral blood samples of 37 consecutive patients with B-cell chronic lymphocytic leukemia (B-CLL) and 17 consecutive patients with leukemic immunocytoma (IC) were studied in order to determine quantitative differences in the surface immunoglobulin (slg) density. In 8/37 (21.6%) cases of B-CLL and 1/17 (5.9%) cases of IC slg staining remained in the control level. Analysis of slg-positive cases demonstrated a close association between the amount of slg and diagnosis: per case the mean calculated fluorescence intensity for IC lymphocytes was 209.7 arbitrary linear intensity units (IU) (median: 156.4, standard error of the mean (SEM): 53.7) and for B-CLL lymphocytes 10.8 IU (median: 7.3, SEM: 1.1; p less than 0.0001). Altogether, 94.6% of all B-CLL patients and 76.5% of all IC patients were correctly classified when a cut-off point was fixed at a mean fluorescence intensity value of 20.0 IU. The percentage of leukemic cells as characterized by CD19 and HLA-DR reactivity was significantly lower in cases of IC (p less than 0.03 and p less than 0.01, respectively). In both entities disease progression occurred more frequently in advanced stages (II-IV) according to the Rai classification (p less than 0.01). In progressive disease rather than in stable disease circulating T lymphocytes were shown to express decreased amounts of surface CD3 antigen (p less than 0.02). We conclude that the quantitative assessment of surface antigens in addition to their qualitative characterization provides accurate information. In particular, the diagnostic discrimination between B-CLL and IC may be improved by determining the lymphocytes' slg amount.

Immunohistologic analysis of small lymphocytic infiltrates of the orbit and conjunctiva

In a prior study we reported that monotypic immunoglobulin expression significantly correlated with an increased risk of dissemination by small lymphocytic infiltrates (SLIs) of the orbit and conjunctiva. However, less than half of all monotypic SLIs disseminated. In this study, we applied a large panel of monoclonal antibodies to cryostat sections of orbital and conjunctival SLIs to address two questions. First, might immunohistologic results other than immunoglobulin staining predict which patients with monotypic SLIs will develop disseminated lymphoma? Second, what is the usefulness of these findings in the diagnosis of orbital and conjunctival SLIs? We found that immunohistologic results did not significantly predict or correlate with disseminated lymphoma in patients with monotypic SLIs, either at time of presentation (ie, staging evaluation positive) and/or subsequently. However, three monotypic infiltrates (10%) had a proliferative rate (Ki-67-positive) of 20% or greater, and all three cases disseminated. Regarding the usefulness of the antibody panel, a B to T cell ratio of 4 or greater (76%), anomalous pan-T cell antigen expression by B cells (38%), and pan-B cell antigen loss (15%) were found exclusively in monotypic SLIs. Combining these results, 80% of monotypic SLIs had additional immunophenotypic criteria of lymphoma. Thus, these findings appear to be useful, although less helpful than immunoglobulin staining, and provide another means of immunophenotypic diagnosis when the results of immunoglobulin staining are technically unsatisfactory or difficult to interpret. We were unable to detect anomalous antigen expression or antigen loss in polytypic infiltrates, including one lesion which locally recurred 30 months later as a histologically indistinguishable, clearly monotypic SLI. We attribute the absence of these findings in polytypic SLIs to their relatively infrequent occurrence in monotypic infiltrates and/or to our inability to detect small clones of malignant cells (if present) by our immunohistologic methods.

Expression of the activation antigen, 4F2, by non-Hodgkin's lymphomas of B-cell phenotype

The monoclonal antibody, 4F2, which reacts with an antigen expressed by activated and proliferating cells, was applied to frozen sections of nine reactive lymphoid lesions, 146 B-cell non-Hodgkin's lymphomas (NHL), and six plasmacytic neoplasms. In reactive cases, the 4F2 antigen was expressed by germinal center cells and interfollicular immunoblasts, the activated or proliferating lymphoid cells, and histiocytes. In the malignant cases, the 4F2 antigen was expressed by 94 (64%) B-cell NHL and all six plasma cell tumors. The incidence of positivity and intensity of expression loosely correlated with the three morphologic grades of NHL identified in the Working Formulation. Approximately one half of all low-grade lymphomas, two thirds of intermediate-grade lymphomas, and all high-grade lymphomas were 4F2 positive. Similarly, the mean intensity of 4F2 antigen expression increased with higher grade. However, for certain histologic subtypes, 4F2 antigen expression did not correlate with morphologic grade. For example, in the intermediate-grade category less than one half of diffuse small cleaved cell lymphomas were 4F2 positive, and expression was weak, similar to that of low-grade lymphomas. In contrast, all other histologic subtypes of lymphoma in the intermediate-grade category were strongly 4F2 positive. Expression of 4F2 antigen also correlated with plasmacytoid differentiation. Seventy-three percent of plasmacytoid small lymphocytic lymphomas (compared with 31% of cases of non-plasmacytoid small lymphocytic lymphoma/chronic lymphocytic leukemia) and all plasma cell neoplasms expressed the 4F2 antigen, the latter cases strongly.

Dendritic reticulum cell-related immunostaining for laminin in follicular and diffuse B-cell lymphomas

We performed a comparative immunohistocytochemical study of the distribution patterns of laminin and follicular dendritic reticulum cells (DRCs) within their follicular microenvironment in both nodular or diffuse B-cell non Hodgkin's lymphomas (NHLs). Twenty nine cases of immunophenotypically diagnosed B-cell NHLs (19 of follicular center cell origin-FCCL- and 10 of the diffuse well differentiated lymphocytic type-WDLL-) and five reactive lymph nodes with follicular hyperplasia were analyzed by immunoperoxidase and immunofluorescence techniques. Serial frozen sections and cytospin preparations were tested either with single antibodies anti laminin and DRC-1, or paired reagents in double labeling immunofluorescence. Our results indicated consistently that within both the reactive germinal centers and the neoplastic nodules of FCCL laminin immunostaining visualized a punctate-granular pattern apart from the linear vascular basement membrane positivity. Double immunofluorescence assay demonstrated that there was a close parallelism between this laminin staining pattern and DRC-1 distribution showing a well developed DRCs meshwork; in the diffuse tumour areas of both FCCL and WDLL, laminin immunoreactivity was found only in those cases in which nests of DRCs were observed. Double immunofluorescence studies performed on cytospin preparations demonstrated that the groups of cells containing DRC-1 positive cells, contained a positivity for laminin, although within the cell the staining for DRC-1 was intense and diffuse, while that for laminin was granular and more sparse. Our results suggested that these laminin and DRC-1 positive reactive sites may be present on the same cells. Since the reduction in number or loss of both DRCs and their related immunostaining for laminin within the microenvironment was consistently associated with a loss of nodularity by lymphoma cells, whereas nodularity in reactive and neoplastic conditions was associated with a rich DRCs meshwork and the related laminin immunostaining, a trapping function of DRCs exercised in the presence of laminin should be considered.

Imprint cytology of non-Hodgkin's lymphomas based on a study of 212 immunologically characterized cases: correlation of touch imprints with tissue sections

The classification of non-Hodgkin's lymphomas (NHLs) has been traditionally based on analysis of histologic sections and has been supplemented more recently by immunologic marker studies. It was the purpose of the present study to illustrate, side-by-side, sections and Romanowsky-stained imprints from the same surgical specimen from practically all categories of immunophenotyped NHLs, including rare and atypical variants that were difficult to classify from the histologic sections alone. Our results indicate that imprint cytology may reveal nuclear and cytoplasmic details not discernible in even the best tissue sections and that it may be selectively helpful in contributing to the classification of NHLs. Our results also show that the relative value of imprint cytology in the classification of malignant lymphomas varies greatly among categories. Specifically, we have found that imprints assist in three ways: the recognition of plasmacytoid features in small cell lymphocytic lymphomas, the recognition of plasmacytoid immunoblastic lymphoma, and the differentiation between NHLs which may be difficult to distinguish histologically. These include (1) small lymphocytic lymphoma versus lymphocytic lymphoma of intermediate differentiation, (2) true histiocytic malignancies versus large cell malignant lymphomas with abundant cytoplasm and/or phagocytosis, (3) anaplastic myeloma versus plasmacytoid immunoblastic lymphoma, (4) large noncleaved versus plasmacytoid immunoblastic lymphoma, (5) lymphoblastic lymphoma versus diffuse small cleaved cell lymphoma, and (6) lymphoblastic lymphoma versus small noncleaved cell lymphoma. Lymph node imprints are easy to prepare and readily interpretable by those experienced in the study of abnormal blood and bone marrow films. Their value as an ancillary methodology aimed at optimal accuracy in the classification of NHLs should be recognized.

Immunophenotypic spectrum of plasma cell leukemia

Four cases of plasma cell leukemia (PCL) are reported that illustrate the variable immunotype of this disorder in contrast with the immunologic profile described for normal B-cell maturation and typical multiple myeloma (MM). Mature B-lymphocytes express B1 antigen (Ag) and surface immunoglobulin (SIg) whereas maturation to the plasma cell stage is accompanied by loss of these immunologic markers and expression of T10 Ag, plasma cell Ag (PCA), and cytoplasmic immunoglobulin (CIg). Plasma cells from patients with MM have previously been found to express the immunophenotype of normal plasma cells. In contrast, none of the four cases reported here express an immunologic profile typical for specific B-cell differentiation stages. Only one of four cases was strongly positive for PCA but additionally expressed B1 Ag and SIg. Of the remaining three cases, all expressed T10 Ag and CIg; two cases also expressed SIg, weak PCA, and B1 Ag. All four cases were monoclonal for lambda light chains and negative for common ALL Ag (CALLA). The variable expression of mature B-cell markers and plasma cell markers demonstrates the immunophenotypic spectrum of PCL; the prognostic significance of this heterogeneity needs to be more closely examined.

The dendritic reticulum cell pattern in B cell lymphomas of the small cleaved, mixed, and large cell types: an immunohistochemical study of 48 cases

An immunohistochemical study was designed to study the dendritic reticulum cell (DRC) patterns in 48 cases of B cell non-Hodgkin's lymphomas of the small cleaved, mixed, and large cell types, both follicular (20 cases) and diffuse (28 cases), in order to evaluate the possible influence of DRCs on homing and the differentiation of neoplastic B cells. Three DRC patterns were observed. In the follicular lymphomas, DRCs constituted nodular networks of variable density. In the diffuse lymphomas, DRCs were present either as isolated and scattered cells (17 cases) or constituted irregular meshworks of variable sizes (11 cases). These DRC patterns correlate with B cell immunophenotypes. Like follicular lymphomas, and unlike diffuse lymphomas without DRC networks, diffuse lymphomas with DRC networks constantly expressed the pan B antigens and one marker characteristic of normal germinal center cells, CD21 antigen, the C3d receptor. The finding of organized DRC networks in a significant number of diffuse lymphomas does not substantiate the hypothesis that DRCs may play a role in the homing of neoplastic B cells. The correlations observed between DRC patterns and B cell immunophenotypes suggest that the persistence and/or the development of DRC networks within follicular center cell-type lymphomas are related to the degree of functional differentiation of neoplastic B cells.

T-cell-rich lymphoproliferative disorders. Morphologic and immunologic differential diagnoses

To differentiate peripheral T-cell lymphomas (PTCL), the authors evaluated the results of T11 monoclonal antibody studies on consecutive cell suspensions prepared from 509 lymph nodes from various lymphoproliferative disorders (LPD). They used T11 (CD2) positivity to identify those LPD in which the content of T cells was high. There were 266 (52%) cell suspensions which contained more than 50% T11-positive cells. More than 75% of the following non-Hodgkin's lymphomas had over 50% T11-positive cells: diffuse mixed cell (DM), diffuse atypical poorly differentiated lymphocytic and lymphoblastic lymphomas; mycosis fungoides; and true histiocytic lymphoma. Eleven cell suspensions had more than 90% T11-positive cells; four were involved by B-cell lymphomas. The cell suspensions prepared from nine of 14 diffuse large cell lymphomas of the T-cell type had more than 50% T11-positive cells. Of these, three of five cases of the polymorphous subtype had fewer than 50% T11 cells, but six of seven lymph nodes of the clear-cell type had more than 50% T11-positive cells. Each of seven DM samples of the T-cell type contained over 50% T11 cells; none had a polymorphous appearance. In the 112 cases of reactive LPD studied, more than 75% of cases of necrotizing lymphadenitis, dermatopathic lymphadenitis, angioimmunoblastic lymphadenopathy, and those with lymph nodes with no specific reactive pattern had more than 50% T11-positive cells. The authors' findings indicate that T11 positivity is a reliable T-cell marker in reactive and neoplastic LPD except for those cases of PTCL with a polymorphous appearance; these tend to lose T11-expression. A multi-parameter diagnostic approach is required in the following LPD: (1) PTCL which are T11-negative; (2) PTCL of small lymphocytic type having an unremarkable T-cell phenotype; (3) SIg-negative B-cell lymphomas which are rich in nonneoplastic T cells; (4) non-Hodgkin's lymphomas with minimal disease which are rich in reactive T cells; and (5) polymorphous large cell proliferations.

Intermediate lymphocytic lymphoma: an immunophenotypic study with comparison to small lymphocytic lymphoma and diffuse small cleaved cell lymphoma

Sixteen cases of intermediate lymphocytic lymphoma (ILL), including eight cases with mantle zone architecture, were studied using cryostat sections, a biotin-avidin immunoperoxidase technique, and a large panel of monoclonal antibodies. The neoplastic cells invariably expressed IgM, most B lineage antigens (B1, TO15, Leu-12, 6A4, 41H, BA-1, and LN-2), and Ia. IgD was expressed in 12 cases. Leu-1 and Leu-8 were weakly expressed by the tumor cells in 12 and 11 cases, respectively. The neoplastic cells did not express common acute lymphoblastic leukemia antigen (CALLA) or the T10 antigen in any case. Because ILL is difficult to differentiate from small lymphocytic lymphoma (SLL) and diffuse small cleaved cell lymphoma (DSCCL) on the basis of light microscopic criteria, the immunologic findings of ILL were compared to 31 cases of B cell SLL and 11 cases of B cell DSCCL previously studied in the laboratory to determine if immunologic findings might aid in the distinction. No absolute, and five statistically significant, differences were found; IgD in combination with IgM was seen more commonly in cases of ILL and DSCCL than in SLL (P less than .01), IgG was found more often in SLL than in ILL and DSCCL (P less than .05), Leu-8 was more commonly expressed in ILL and SLL than in DSCCL (P less than .05), T9 expression was less frequent in ILL as compared with SLL (P less than .05) and more proliferating cells were seen in ILL and DSCCL than in SLL (P less than .01). The investigators conclude that these three classes of lymphoma are remarkable much more for their immunologic similarities than for their differences and that immunologic studies are of limited usefulness in differentiating the three neoplasms. Their results also support the concept that these lymphomas are closely related to each other. In particular, DSCCL immunologically appears to be more closely related to SLL and ILL than to follicular small cleaved cell lymphoma.

Immunophenotypic differences between plasmacytoma/multiple myeloma and immunoblastic lymphoma

Four cases of plasmacytoma (PC), six cases of multiple myeloma (MM), and nine cases of immunoblastic lymphoma (IL) of B-cell phenotype were studied with a large panel of monoclonal antibodies applied to frozen tissue sections. There were no significant differences in the immunophenotypes of plasmacytomas and multiple myelomas. However, significant immunophenotypic differences were noticed between the plasmacytoma/multiple myeloma cases (PC/MM) and the immunoblastic lymphoma specimens. The PC/MM cases characteristically stained with alpha (or gamma) and T10 and did not usually stain with mu, leukocyte common antibodies, certain B-lineage antibodies (B1, T015, 4G7, 6A4), or Ia. In contrast, IL sections usually did not stain with alpha or T10 and generally did stain with mu (or gamma), leukocyte common antibodies, B-lineage antibodies, and Ia. Ki-67, an antibody to proliferating cells, stained significantly fewer cells in PC/MM than in IL and stained significantly fewer cells that had a good clinical outcome. We conclude that although no one antibody is useful in distinguishing PC/MM from IL, the application of a panel of antibodies may be helpful in making this distinction. The prognosis may correlate with the numbers of proliferating cells as measured by reactivity with Ki-67.

Activation and differentiation antigen expression in B-cell non-Hodgkin's lymphoma

In an attempt to establish whether extended immuno-phenotyping allows more accurate definition of subgroups of B-cell non-Hodgkin's lymphoma (NHL) we have stained a series of 145 cases with a large panel of monoclonal antibodies that recognize B-cell differentiation and activation antigens. No antigen was expressed by all cases. The B-cell histogenesis in many cases could be confirmed only by using a panel of immunoglobulin and pan B-cell markers. There was marked phenotypic heterogeneity within and between major groups of B-cell NHL as delineated by the Kiel classification although the differentiation antigens CD5 (lymphocytic and centrocytic NHL) and OKT10 (plasma cell tumours) were more often expressed by certain morphological groups. The activation antigens 4F2 and transferrin receptor were expressed more strongly and more often by high grade NHL but other activation antigens (CD23 and CD25) were not more frequently associated with these tumours. Extended phenotyping may be of value in improving the understanding of biological abnormalities and processes involved in B-cell NHL, but we conclude that a limited panel of markers (CD3, CD5, CD22, CD45, IgM, kappa, and lambda) should be sufficient for routine diagnosis and classification of most cases.

Lymphoplasmacytoid lymphoma: an immunohistological study

Eighteen cases of lymphoplasmacytoid lymphoma (LPL) have been immunophenotypically characterized with a panel of 26 monoclonal antibodies. All cases expressed leucocyte common antigen, class II MHC and stained with B cell markers (CD19, CD20, CD22) although a variable proportion of tumour cells were noticed to have lost some B cell marker expression. There was some phenotypic heterogeneity with variable immunostaining with KB61, CD21, and CD5. A variable proportion of cells in all cases contained cytoplasmic immunoglobulin. Surface immunoglobulin light chain restriction was demonstrated in 11 cases and heavy chain predominance in 16 cases. Few tumour cells were proliferating as indicated by Ki67 immunostaining. A wide variation in number of macrophages and T lymphocytes were present in association with the tumours. A significant association between the expression of CD5 and the presence of peripheral blood lymphocytosis was noticed (p less than 0.003) but there was no association between CD5 and co-expression of IgM and IgD. This data supports an origin from non-germinal centre cells for LPL and suggests that CD5 expression by B cells may be related to lymphocyte migration. LPL shows some immunological heterogeneity and can present diagnostic difficulties, but its poor prognosis makes it an important category of lymphoma to recognise.

Immunohistochemical staining of non-Hodgkin's lymphoma in paraffin sections using the MB1 and MT1 monoclonal antibodies

We have performed a single blind trial to assess the value of the monoclonal antibodies MB1 and MT1 in lymphoma classification. Sixty cases of non-Hodgkin's lymphoma (NHL) were stained with MB1 and MT1 using an indirect immunoperoxidase technique in paraffin sections. The majority of B tumours (27/33) stained with MB1, and most of the T tumours (24/27) stained with MT1. The MB1 antibody often produced rather weak staining but it was apparently highly specific for B cells, with only three (3/27) of the T tumours (two cases of 'malignant histiocytosis' of the intestine (MHI) and one pleomorphic T-cell lymphoma) displaying 'false' positivity. The MT1 antibody generally produced very strong staining, but it was not very selective, with 14/33 of the B lymphomas displaying 'false' positivity. the cross-reactivity observed in 17 cases led to only three misdiagnoses, two B tumours being designated as T lymphomas and one T tumour being designated as a B lymphoma. In a few cases (7/17), dual staining with both antibodies precluded firm diagnosis. In other cases (6/17), classification was possible despite some of the tumour cells showing dual staining. The seventeenth case was a plasmacytoma displaying MT1 positivity only. While the monoclonal antibodies MB1 and MT1 are of use in classifying lymphomas in paraffin section, they are not entirely lineage-specific, and the uncritical use of these two reagents alone may give rise to misdiagnosis; the use of a panel of monoclonal antibodies may yield more accurate results. As with any immunohistochemical marker, their limitations should be recognized; interpretation must be judicious and always in the context of the histological appearances.

Intermediate lymphocytic lymphoma: an immunohistologic study with comparison to other lymphocytic lymphomas

In an immunohistologic analysis of 13 cases of intermediate lymphocytic lymphoma (ILL), the immunophenotype of ILL was compared to the immunophenotypes of other B-lymphocytic lymphomas and the normal lymphoid follicle to determine the normal cell in the scheme of B-cell differentiation that corresponds to ILL. The characteristic immunophenotype of ILL was surface IgM +/- D+, cytoplasmic immunoglobulin -, B1+, BA1+, B2-, BA2-, B4+, Leu 14+, HLA-DR+, Leu 1+, and common acute lymphoblastic leukemia associated (CALLA) antigen -. The immunophenotype of ILL was similar to that of lymphocytes in normal primary follicles and the mantle zones of secondary follicles. The "immature" phenotype of ILL was identical to that of small lymphocytic lymphoma, which strongly supports their close lineage relationship. In contrast, the "mature" phenotypes of the follicular center cell and lymphoplasmacytoid lymphomas suggest that they correspond to normal cells at later stages of differentiation. Our findings indicate that B-lymphocytic lymphomas recapitulate the normal stages of B-cell differentiation. The cell of ILL appears to be an immature B cell that homes to, and resides in, primary follicles and the mantle zones of secondary follicles. The cytologic, architectural, immunologic, and clinical features of ILL indicate that it should be included as a separate category in the International Working Formulation.

Lymphoid stromal reaction in gastrointestinal lymphomas: immunohistochemical study of 14 cases

The lymphoid stromal reaction, particularly the T lymphoid reaction, was studied immunohistochemically on cryostat sections in 14 cases of primary gastrointestinal B lymphomas, and compared with the type and distribution of lymphoid cells in three cases of gastric lymphoid hyperplasia. A pronounced T lymphoid reaction, mainly of the T helper phenotype, occurred in both lesions. Most of these T cells bore HLA-DR antigens, but only a few of them had the receptor for interleukin 2. The T lymphoid reaction was observed inside the lymphomas in seven of a total of 14 cases, and around the lymphomas in four of the six cases clinically classified as stage I. Perivascular mucosal and submucosal nodules, entirely composed of T cells, seemed characteristic of gastric lymphoid hyperplasias. A T lymphoid reaction in lymphoid hyperplasias suggests an amplification of the cell mediated immune response; in lymphomas it could represent a host reaction against the lymphomatous infiltrate, therefore favouring a better prognosis.

Immunophenotypes in "well-differentiated" lymphoproliferative disorders, with emphasis on small lymphocytic lymphoma

The histologic, immunophenotypic, and clinical findings in 24 cases of "well-differentiated" lymphoproliferative disorders are presented, with an emphasis on small lymphocytic lymphoma (SLL; well-differentiated lymphocytic lymphoma, WDLL). SLL was diagnosed in 18 patients, Waldenström's macroglobulinemia in one, mantle zone lymphoma (MZL) in four, and intermediate differentiated lymphocytic lymphoma (IDL) in one. Immunophenotypic analysis revealed one SLL to be of T-cell derivation, while a monoclonal B-cell phenotype was found in the remaining 23 patients; 20 of these neoplasms co-expressed the pan-T-cell antigen Leu-1. This included three of the four patients with MZL and the patient with IDL. All SLLs with pseudofollicular growth centers stained for transferrin receptor. Additionally, a survey of 248 non-Hodgkin's lymphomas of all types revealed four of 70 patients with B-cell large cell lymphoma (LCL; diffuse histiocytic lymphoma, DHL) that also co-expressed the same Leu-1 antigen. Immunoperoxidase study of both frozen tissue sections and cytocentrifuge preparations eliminated the limitations of faint antigen expression and/or interstitial immunoglobulin staining. In addition to detailing the immunophenotype of SLL, the immunologic kinship of MZL/IDL to SLL and the uncommon co-expression of Leu-1 in B-cell LCLs are demonstrated.

Neoplastic plasma cells in follicular lymphomas. Clinical and pathologic findings in six cases

Six cases of follicular lymphoma contained an abundant plasma cell component. With immunoperoxidase techniques, this was found to demonstrate monotypic cytoplasmic marking for either K or L Ig light chain in five cases, and for IgA heavy chain only in one case. A histogenetic relationship between follicular center cells and plasma cells was suggested by cell forms morphologically intermediate between these two types and by monotypic plasma cells in the neoplastic follicles. The progressive differentiation of follicular center cells into Ig-secreting cells in these cases is likely to be the result of an alteration of the immunoregulatory mechanisms that usually block the differentiation of follicular lymphomas. Four of our patients presented with disseminated disease, three had extranodal presentation and four manifested serum paraproteins. Their median survival was 40 months; two of them died of disease. The published data and our own suggest that follicular lymphoma with plasmacytic differentiation is a malignancy of intermediate grade, with survival and clinical features closer to lymphoplasmacytic/lymphoplasmacytoid lymphoma (LP immunocytoma) than to follicular lymphoma.