Molecular heterogeneity of splenic marginal zone lymphomas: analysis of mutations in the 5' non-coding region of the bcl-6 gene.

Splenic marginal zone lymphoma (SMZL) has been recognized as a distinctive type of small B cell lymphoma, and defined on the basis of its morphological, phenotypic, clinical and molecular characteristics. In spite of this, the borders of the entity, the homogeneity of the cases and the presumably cell origin of SMZL remain controversial issues. The frequency of mutation in the 5' non-coding region of the bcl-6 gene has been used as a marker of germinal center derivation, which may be used to establish the molecular heterogeneity of different non-Hodgkin lymphoma (NHL) types. This roughly parallels the characteristics and frequency of the somatic hypermutations found in the immunoglobulin heavy chain variable region (IgVH) genes. This study analyzed mutations of bcl-6 in the 5' non-coding region in 22 SMZL cases and, for the purpose of comparison with different B cell subsets, in microdissected germinal centers, mantle zones and marginal zone subpopulations from reactive splenic lymphoid follicles. A majority of the SMZL cases studied, 19/22 (87%), bear unmutated bcl-6 gene, while mutation was only observed in 3/22 (13%) cases. Analysis of normal B cell subpopulations showed bcl-6 hypermutation in 3/10 (30%) germinal center clones, 5/14 (35%) marginal zone clones; and unmutated sequences in all clones derived from mantle cells. The frequency of these mutations in normal spleen confirms previous findings on the hypermutation IgVH process in normal B cell populations. The data presented here support the existence of molecular heterogeneity in this entity, and give additional results in favor of the hypothesis that, in spite of initial morphological observations, a significant proportion of SMZL cases could derive from an unmutated naive precursor, different from the marginal zone, and possibly located in the mantle zone of splenic lymphoid follicles. Thus the marginal zone differentiation of these tumors could be related more with the splenic microenvironment than it is to the histogenetic characteristics of the tumor.

Monocytoid B cells. A comparative clinical pathological study of their distribution in different types of low-grade lymphomas.

Neoplastic monocytoid B-cells (MBCs) are present in different amounts in several types of non-Hodgkin's lymphomas (NHLs), including monocytoid B-cell lymphoma (MBCL), splenic marginal zone lymphoma (SMZL), mucosa-associated lymphoid tissue (MALT) low-grade B-cell lymphomas, and follicular centroblastic-centrocytic (CB-CC) lymphomas. In an attempt to clarify the relationships between different groups of tumors with a significant monocytoid component, we studied six primary lymph node MBCL, three SMZL, seven MALT lymphomas, and four CB-CC with monocytoid differentiation. Their clinical, morphological, immunohistochemical and molecular features were compared. The results show wide overlapping between MALT and MBCL in terms of morphology, immunophenotype, and molecular features. Follicular colonization was a characteristic finding in both groups. Some MBCL revealed mucosal involvement during the course of the disease, suggesting a possible MALT origin. Our data support the suggestion that the use of the term MBCL should be discontinued in cases with mucosal involvement, as they are probably examples of lymph node involvement brought about by MALT lymphomas. Although SMZL have some overlapping features with MBCL and MALT lymphomas, some of the clinical and morphological specific findings justify their distinction from the other groups. The CB-CCs with monocytoid differentiation frequently harbored t(14;18), lacking any significant differentiating features from conventional follicular CB-CC lymphomas. Additional studies are needed to define the molecular features of MBCL and other marginal zone tumors.

Splenic marginal zone lymphoma: a distinctive type of low-grade B-cell lymphoma. A clinicopathological study of 13 cases.

The recognition and classification of the different varieties of splenic low-grade B-cell lymphomas have been hampered by the rarity of histological studies of surgical splenectomy specimens of B-cell lymphoma. In an effort to characterize the recently described splenic marginal zone lymphoma (SMZL), we conducted a survey of 13 patients with this type of tumor using the criteria defined by Schmid for its recognition (Schmid et al., Am J Surg Pathol 1992;16:455-66). Primary splenic high-grade lymphomas, T-cell lymphomas, and secondary infiltration by other recognized low-grade B-cell lymphomas, with the exception of splenic lymphoma with villous lymphocytes, were excluded. This selection gave rise to a homogeneous group of tumors with similar clinical, histological, immunohistochemical, and molecular features. Our study showed the critical parameters for their recognition to be morphological, including macroscopic micronodularity and the constant presence of white- and red-pulp infiltration, marginal zone pattern, and plasmacytic differentiation. No t(14;18) or PRAD-1/cyclin D1 overexpression was detect able in any case. Clinically, the tumors were widespread with a protracted evolution. Nodal infiltration by SMZL in our cases was morphologically similar to monocytoid B-cell lymphoma. SMZL could constitute the largest group of primary splenic malignant lymphomas, partially overlapping with splenic lymphoma with villous lymphocytes. Specific molecular markers for SMZL have yet to be defined. Because of the limited number of cases, the question of therapy for this group of lymphomas must remain open for the future.

Progression to large B-cell lymphoma in splenic marginal zone lymphoma: a description of a series of 12 cases.

Splenic marginal zone lymphoma (SMZL) is considered to be an indolent extranodal B-cell lymphoma. Despite its low aggressivity, histologic progression has been described in sporadic reports, although the frequency, characteristics, and underlying molecular abnormalities of this phenomenon are largely unknown. We review here the clinical, morphologic, immunohistochemical, and molecular features of a series of 12 SMZL cases that showed progression to large B-cell lymphoma (LBCL). The most frequent location of secondary LBCL was in peripheral lymph node. This occurred between 12 and 85 months after diagnosis of SMZL. However, in two cases LBCL was diagnosed at the initial stage of the disease (one spleen tumoral nodule and one hilar lymph node). The histologic and immunophenotypic features of these cases were similar to those of transformed LBCL at other sites. In four cases the immunoglobulin heavy chain gene polymerase chain study revealed the same rearrangement pattern in both primary and secondary tumors, thereby confirming their identity and excluding the possibility of a second malignancy. As is the case with other low-grade lymphoproliferative disorders, SMZL may undergo high-grade transformation. These 12 cases represent 13% of our series of SMZL with adequate follow-up. The incidence of large cell transformation in SMZL seems to be lower than in follicular lymphoma (25-60%) and mantle cell lymphoma (11-39%), although it is similar to the frequency of transformation in B-chronic lymphocytic lymphoma/small lymphocytic lymphoma (1-10%). The mean proliferative index (MIB1 staining) in initial SMZL specimens of cases with LBCL transformation was 28.6%, higher than that of MIB1 staining in the overall SMZL series (21.8%), although not statistically significantly so. p53 or p16INK4a inactivation in this series was observed in only one case, in contrast with the situation observed in chronic lymphocytic leukemia, follicular lymphoma, and mantle cell lymphoma. It seems that progression in SMZL is mainly independent of p53 or p16INK4a inactivation. The frequency of the 7q deletion in this series was 3 of 7 (42%). 7q loss may play an alternative role in the inactivation of the p53 and p16INK4a pathway, thereby favoring tumoral progression.

Primary cutaneous large B-cell lymphoma: the relation between morphology, clinical presentation, immunohistochemical markers, and survival.

The histogenesis, morphology, immunophenotype, and clinical behavior of cutaneous large B-cell lymphomas (CLBCL) are largely a matter of controversy. We performed an investigation to determine whether CLBCL have features that differentiate them from other large B-cell lymphomas and whether CLBCL is itself a heterogeneous group. To this end, we reviewed the main characteristics of a series of 32 cases of LBCL found in the skin. We reviewed the clinical findings and paraffin sections of the tumors from these 32 patients. The immunohistochemical study performed included p53, MIB1, Bcl2, Bcl6, and CD10 markers. We carried out statistical analysis of these data (univariate and multivariate), seeking an association between the features of the tumors and clinical outcome, as defined by failure-free survival time. Only one patient died as a consequence of the lymphoma. Nevertheless, the accumulated probability of survival without failure at 48 months was 0.46. The number, type, and localization of the lesions were not associated with variations in either survival or failure-free survival. The expression of p53 was negative in this group of CLBCL, whereas Bcl-2 expression or localization in the lower leg did not relate to any other significant feature. Histologic examination of the cases disclosed three different groups: Grade III follicular lymphomas (FLs), monomorphous large B-cell lymphomas (LBCL type I), and LBCL with an admixed component of small B-lymphocytes (LBCL type II). Grade III FL (11 cases) tended to be found in the head and neck and showed CD10 expression in a majority of cases. A higher probability of lymph node relapses was associated with cases located in the head and neck and with CD10+ tumors. Cutaneous large B-cell lymphomas are indolent tumors, but follow an insidious course. Our data support the interpretation that CLBCL is a heterogeneous condition; comprises some LBCL derived from CD10+ germinal center cells which manifests more frequently as tumors in the head and neck region, with an increased probability of relapse in lymph nodes [1] and has some distinctive morphologic features. The existence of a component of small B-cells within the other CLBCL could lend support to the theory that some of these tumors, more than arise de novo, may have originated in preexistent small B-cell lymphomas, but no firm evidence of this is provided in this study.

The detection of B-cell monoclonal populations by polymerase chain reaction: accuracy of approach and application in gastric endoscopic biopsy specimens.

The recently developed strategy for the detection of monoclonal B-cell populations, based on the selective amplification of predominant immunoglobulin heavy chain gene (IgH) rearrangement, is seen to be a suitable alternative to Southern blot analysis. The new technique uses a pair of consensus primers for variable (VH) and joining (JH) regions. We first tested the accuracy of this new approach on a broad series of 67 samples that had been well characterized by both Southern blot and immunohistochemical techniques before being subjected to blind testing. Our results show that this technique gave 100% specificity (absence of false-positive results) and approximately 70% sensitivity (30% false-negative results). The only exception was the presence of an IgH polymerase chain reaction ambiguous result in a case of Sezary's syndrome. The polymerase chain reaction technique was then applied to a panel of 27 frozen gastric endoscopy biopsy specimens following previous clinical suspicion of lymphoma. Monoclonality was detected in nine of 13 samples previously diagnosed as lymphomas and in one of two carcinomas. Further examination of the gastrectomy specimen in the latter case disclosed a B-cell lymphoma associated with the carcinoma. In spite of its limited sensitivity, the high specificity attained by this technique in the detection of monoclonality makes it a useful adjunct to routine morphologic criteria, as it is sometimes capable of detecting true positive cases that conventional morphology studies show to be negative.

Splenic marginal zone lymphoma with increased number of blasts: an aggressive variant?

Splenic marginal zone lymphoma (SMZL) is a recently described and distinctive type of splenic lymphoma and is characterized by an indolent clinical course. By analyzing a large series of SMZL cases, we recognized the existence of a subset of 6 cases characterized by an aggressive clinical course that led to death caused by the tumor in 5 of 6 cases, whereas the remaining patient showed signs of tumor progression. The morphological, immunohistological, and molecular study of these cases has allowed us to detect precise distinctive features of this SMZL variant. The cases included here were characterized by massive splenomegaly and a morphological picture showing a micronodular pattern of splenic involvement with follicle replacement, biphasic cytology, and marginal zone differentiation. Unlike classical SMZL cases, a conspicuous component of larger lymphocytes was distributed in the marginal zone ring, occasionally overrunning it, with isolated presence of the same cells within the central small cell component and also in the red pulp. The bone marrow and peripheral lymph nodes showed similar histological findings to those described for SMZL in these locations. The genetic and molecular study of these cases showed no alterations specific to other lymphoma types, such as t14;18 and t11;14. Instead of this, it showed 7q loss in 3 of 5 cases, p53 inactivation in 2 of 6 cases, cyclinD1 overexpression in 2 of 6 cases, and the presence of translocations involving the 1q32 region in 2 of 4 cases. The recognition of this aggressive variant, besides offering a prognostic indication, could lead to a more suitable form of clinical management of these patients. Further molecular studies would clarify the role of the different genetic alterations found.

Value of PCR detection of TCR gamma gene rearrangement in the diagnosis of cutaneous lymphocytic infiltrates.

In this study, we analyzed the reliability and usefulness of the polymerase chain reaction (PCR) for the detection of T-cell receptor (TCR)gamma gene monoclonal rearrangement. We first tested for the specificity and sensitivity of this strategy, against the classical criteria of Southern blot analysis (SBA). Of the 27 samples tested, results agreed in all but two. Broader analysis of these cases demonstrated the high specificity (absence of false positives) of the PCR strategy, together with its limited sensitivity (10% of false negatives). The usefulness of this PCR approach was then tested on a panel of 28 biopsy specimens of cutaneous lymphocytic infiltrates. Monoclonal TCR gamma rearrangement was detected in seven of eight cases of early stage mycosis fungoides (MF), one of two Sezary syndrome (SS) cases, two of two non-MF T-cell lymphoma, and two of three lymphomatoid papulosis. Monoclonality was not detected in any of the 11 benign cases (parapsoriasis and inflammatory dermatosis). Results obtained with this new molecular strategy provide additional support for the hypothesis of a monoclonal origin for most early stage T-cell MF. They also suggest the heterogeneous nature of some lymphomatoid papulosis lesions. Therefore, due to the difficulty in detecting T-cell monoclonality by immunohistochemical techniques, PCR can be a useful alternative strategy to SBA. It could also be used as a complementary technique in the routine diagnosis of T-cell cutaneous infiltrates.

[The presence of minimal residual disease during induction therapy is a reliable factor for the prognosis of recurrence in children with standard-risk B-cell precursor acute lymphoblastic leukemia]. / La presencia de enfermedad residual mínima durante la terapia de inducción es un factor fiable para la predicción de recidiva en niños con leucemia linfoblástica aguda de células B precursoras de riesgo estándar.

BACKGROUND: To evaluate the prognostic implications of the presence of minimal residual disease (MRD) during the induction period in children diagnosed with low risk B cell precursor acute lymphoblastic leukaemia (LR-ALL). PATIENTS AND METHODS: In 36 children with LR-ALL treated with BFM-86 protocol, MRD was studied at the end of induction by IgH and TCR delta gene analysis. RESULTS: The probabilities of disease free survival were: 52% (patients with MRD at the end of Induction), 64% (patients with MRD at day 15) and 100% (patients without MRD). CONCLUSIONS: The presence of MRD is a new and useful prognostic factor in LR childhood ALL.

Over 30% of patients with splenic marginal zone lymphoma express the same immunoglobulin heavy variable gene: ontogenetic implications.

We performed an immunogenetic analysis of 345 IGHV-IGHD-IGHJ rearrangements from 337 cases with primary splenic small B-cell lymphomas of marginal-zone origin. Three immunoglobulin (IG) heavy variable (IGHV) genes accounted for 45.8% of the cases (IGHV1-2, 24.9%; IGHV4-34, 12.8%; IGHV3-23, 8.1%). Particularly for the IGHV1-2 gene, strong biases were evident regarding utilization of different alleles, with 79/86 rearrangements (92%) using allele (*)04. Among cases more stringently classified as splenic marginal-zone lymphoma (SMZL) thanks to the availability of splenic histopathological specimens, the frequency of IGHV1-2(*)04 peaked at 31%. The IGHV1-2(*)04 rearrangements carried significantly longer complementarity-determining region-3 (CDR3) than all other cases and showed biased IGHD gene usage, leading to CDR3s with common motifs. The great majority of analyzed rearrangements (299/345, 86.7%) carried IGHV genes with some impact of somatic hypermutation, from minimal to pronounced. Noticeably, 75/79 (95%) IGHV1-2(*)04 rearrangements were mutated; however, they mostly (56/75 cases; 74.6%) carried few mutations (97-99.9% germline identity) of conservative nature and restricted distribution. These distinctive features of the IG receptors indicate selection by (super)antigenic element(s) in the pathogenesis of SMZL. Furthermore, they raise the possibility that certain SMZL subtypes could derive from progenitor populations adapted to particular antigenic challenges through selection of VH domain specificities, in particular the IGHV1-2(*)04 allele.

Lymphocyte predominance Hodgkin's disease (nodular paragranuloma)--a bcl-2 negative germinal centre lymphoma.

Hodgkin's disease, lymphocyte predominance type (nodular paragranuloma), is of germinal centre origin and the tumour cells have a B-cell phenotype. As the T(14;18) translocation, and the subsequent expression of bcl-2 protein by germinal centre cells, is the most characteristic finding of centroblastic-centrocytic lymphoma, we have tested a series of 11 cases of lymphocyte predominance Hodgkin's disease, using Southern blot analysis for the major breakpoint region and the minor breakpoint cluster region, polymerase chain reaction with primers for the major and minor breakpoint cluster region, and immunohistological studies with a monoclonal antibody specific for the bcl-2 protein. All three techniques gave negative results in the cases of Hodgkin's disease, establishing a clear differentiation from centroblastic-centrocytic lymphoma. These findings are useful in the differential diagnosis between the two entities and raise the question of the non-clonal nature of lymphocyte predominance Hodgkin's disease.

True histiocytic lymphoma (monocytic sarcoma)

The clinical, histological, immunophenotypic, and genotypic characteristics of two cases of cutaneous genuine histiocytic lymphoma are described. Both cases presented as cutaneous lesions. Both patients remain alive and free of disease at 26 and 10 months after the diagnosis and after having been treated with polychemotherapy. Neither peripheral blood nor bone marrow infiltration was detected in either case. Histological and immunophenotypic examination showed dense, diffuse dermic infiltrates of mononuclear cells with positive macrophage-associated markers (CD11c, CD68), and negative T- or B-cell-associated antigens. A germline configuration of both T-cell receptor and immunoglobulin genes was observed in gene rearrangement studies. Although most of the cases that have been diagnosed as histiocytic lymphoma or malignant histiocytosis in the past turned out to be B- or T-large-cell lymphomas, a small number of cases (two in our consecutive series of 350 cases) show characteristics of monocyte-macrophage tumors. We stress the importance of the CD68 marker in the diagnosis of true histiocytic lymphoma, suggest a therapeutic approach based on similarities with monocytic leukemia, and propose the use of the term monocytic sarcoma for this clinicopathological presentation.

B-cell clonal detection in gastric low-grade lymphomas and regional lymph nodes: an immunohistologic and molecular study.

Gastric low-grade B cell lymphomas originating in mucosa-associated lymphoid tissues are composed of reactive hyperplastic germinal centers and interfollicular centrocyte-like cells. Their polymorphic, histologic composition and infrequent dissemination beyond the gastric wall led to the denomination of these tumors as "pseudolymphomas." To elucidate their clonal character, a Southern blot study of DNA and immunohistological study was carried out on 14 cases of surgical specimens from gastrectomy (11 low-grade and three high-grade tumors). Monoclonal and polyclonal antibodies were used on frozen and paraffin sections. A mucosa-associated lymphoid tissue origin for the tumors was assigned due to their centrocyte-like morphology and the presence of lymphoepithelial lesions. Southern blot analysis of DNA and immunohistological results confirm the monoclonal composition of gastric low-grade lymphomas in all cases. Although both types of technique correlated well on the predominant light-chain, Southern blot DNA study was nevertheless more sensitive than the immunohistochemical techniques. Surprisingly, in two cases of gastric low-grade lymphoma, Southern blot DNA analysis of histologically reactive regional lymph nodes showed an unexpected immunoglobulin heavy chain gene rearrangement. This coincided with that found in the gastric wall. Results confirm the monoclonal nature of the low-grade gastric lymphoma. This supports consideration of this tumor as an indolent primary lymphoma of the stomach, confirming the suitability of excluding the term "pseudolymphoma." Involvement of regional lymph nodes may be a more frequent occurrence than previously detected through morphological study.

Hepatosplenic gamma-delta T-cell malignant lymphoma: report of the first case in childhood, including molecular minimal residual disease follow-up.

We report the first case of T-cell gamma delta+ hepatosplenic malignant lymphoma in childhood. Tumour-specific oligoprobes were developed against the single V1-J1 rearrangement of the delta T-cell receptor (TCR) gene in order to perform minimal residual disease (MRD) studies. Molecular analysis in serial bone marrow samples proved to be of predictive value concerning the clinical outcome. Clonotypic DNA was not detected in peripheral blood during the course of the disease until a refractory terminal leukaemic phase took place 18 months after the diagnosis. This case demonstrates the usefulness of MRD studies to monitor the course of disease in at least some subsets of peripheral T-cell lymphomas.

7q31-32 allelic loss is a frequent finding in splenic marginal zone lymphoma.

Splenic marginal zone lymphoma (SMZL) has been recognized as an entity defined on the basis of its morphological, phenotypic, and clinical characteristic features. Nevertheless, no characteristic genetic alterations have been described to date for this entity, thus making an exact diagnosis of SMZL difficult in some cases. As initial studies showed that chromosome region 7q22-32 is deleted in some of these cases, we analyzed a larger group of SMZL and other lymphoproliferative disorders that may partially overlap with it. To better define the frequency of 7q deletion in SMZL and further identify the deleted region, polymerase chain reaction analysis of 13 microsatellite loci spanning 7q21-7q36 was performed on 20 SMZL and 26 non-SMZL tissue samples. The frequency of allelic loss in SMZL (8/20; 40%) was higher than that observed in other B-cell lymphoproliferative syndromes (2/26; 7.7%). This difference was statistically significant (P < 0.05). The most frequently deleted microsatellite was D7S487 (5/11; 45% of informative cases). Surrounding this microsatellite the smallest common deleted region of 5cM has been identified, defined between D7S685 and D7S514. By comparative multiplex polymerase chain reaction analysis, we detected a homozygous deletion in the D7S685 (7q31.3) marker in one case. These results suggest that 7q31-q32 loss may be used as a genetic marker of this neoplasia, in conjunction with other morphologic, phenotypic, and clinical features. A correlation between 7q allelic loss and tumoral progression (death secondary to the tumor or large cell transformation) in SMZL showed a borderline statistical significance. The observation of a homozygous deletion in this chromosomal region may indicate that there is a tumor suppressor gene involved in the pathogenesis of this lymphoproliferative neoplasia.

High expression of the ILT2 (LIR-1) inhibitory receptor for major histocompatibility complex class I molecules on clonal expansions of T large granular lymphocytes in asymptomatic patients.

BACKGROUND AND OBJECTIVES: The lymphoproliferative disorders of large granular lymphocytes (LGLD) are divided into two groups: T-cell type and NK-cell type. These entities may be either asymptomatic or associated with autoimmune manifestations (especially cytopenias). A number of surface receptors, expressed by NK-cells and some T-lymphocyte subsets repress cytotoxicity and cytokine production upon ligation with HLA class I molecules and are clonally expressed in theses lymphoproliferative disorders. These cytotoxic lymphocytes can lyse erythroid progenitors in vitro, and the physiologic lower levels of HLA class I antigens on the erythroid lineage may contribute to this form of autoimmunity. It is conceivable that the clinical outcome of T-LGLD might be influenced by the expression of MHC class I inhibitory receptors. DESIGN AND METHODS: We analyzed the surface expression of these molecules, lectin-like heterodimers (CD94/NKG2A) or killer immunoglobulin (Ig)-like receptors (KIR) and another Ig-like inhibitory receptor, termed ILT2 or LIR-1 in CD8+ cells from 12 cases of ab T-LGLD using specific monoclonal antibodies. RESULTS: None of the LGLD cases had anemia and 11 of 12 patients remain asymptomatic. KIR and CD94/NKG2A expression was detected on CD8+ populations only in some cases of T-LGLD. By contrast, our observations revealed that ILT2 expression was markedly higher in CD8+ cells from LGLD patients than from healthy donors. INTERPRETATION AND CONCLUSIONS: Expression of the ILT2 inhibitory receptor for HLA class I molecules on LGLD cells might indeed contribute to preventing their autoreactivity. Further studies are required to evaluate the expression/function of the ILT2 receptor in patients who eventually become symptomatic. The development of cytopenias in LGLD patients must involve other self-reactive activating receptors. Analysis of the expression and function of triggering NKR in LGLD needs to be carefully addressed.

Splenic small B-cell lymphoma with predominant red pulp involvement: a diffuse variant of splenic marginal zone lymphoma?

AIMS: Splenic marginal zone lymphoma (SMZL) has been characterized by a micronodular pattern of infiltration, biphasic cytology, follicular replacement and the presence of marginal zone differentiation. Here we describe four cases with some distinctive features, such as diffuse splenic infiltration, lack of micronodules, marginal zone cytology, p53 inactivation and cutaneous involvement. METHODS AND RESULTS: In the course of a review of cases of SMZL, we recognized the existence of a subset of four cases of splenic B-cell lymphoma, with predominantly red pulp involvement, absence of follicular replacement, and a monomorphous population of tumoral cells resembling marginal zone B-cells, with scattered nucleolated blast cells. The immunophenotype (bcl2+, CD5-, CD10-, CD43-, CD23-, cyclin D1-, IgD- (3/4)) was consistent with SMZL. Bone marrow infiltration (4/4) and peripheral blood involvement (2/4) showed similar findings to those described for SMZL in these locations. However, unlike classical SMZL, 2/4 had cutaneous involvement, and 4/4 cases showed either p53 mutation or anomalous p53 staining (p53+, p21-). CONCLUSIONS; In spite of a diffuse pattern of splenic infiltration, cutaneous involvement and p53 alterations, these cases have findings that overlap with those corresponding to classic SMZL (symptomatology, morphology of bone marrow, lymph nodes, peripheral blood involvement, and immunophenotype). We suggest that these cases be considered a putative variant of SMZL.

Retinoblastoma (Rb) gene product expression in lymphomas. Correlation with Ki67 growth fraction.

The retinoblastoma susceptibility gene (Rb) has been characterized as a tumour suppressor gene. Rb protein is involved in cell-cycle control, regulating gene transcription. The absence of Rb protein in inherited retinoblastoma has been proved to be the result of inactivation of both Rb alleles through mutation or deletion, according to the general model for suppressor genes. The frequent detection of Rb gene alterations in human tumours (retinoblastoma, osteosarcoma, bladder carcinoma, small-cell lung carcinoma) and the correlation with clinical outcome found in some tumours prompted us to study Rb gene expression in lymphoid tumours in an attempt to determine whether Rb gene expression is related to histological type and degree of aggressivity in human lymphomas. To establish normal levels of Rb protein, its expression was analysed in vitro on cytospin preparations from normal and pokeweed mitogen (PWM) or phytohaemagglutinin (PHA)-stimulated peripheral blood lymphocytes (PBLs), using a monoclonal antibody (PMG3-245). Rb protein expression in vivo was quantified using a computer analysis system (CAS) on frozen sections from reactive and neoplastic lymphoid tissue. As a control of tissue preservation, and to compare Rb expression and growth fraction, the tumours and cells were labelled simultaneously with the Ki67 monoclonal antibody. Normal and stimulated lymphocytes showed a gradual increase of Rb protein during progression of the cell cycle, with a peak in the M phase. G0-G1 cells had no detectable levels of Rb protein, suggesting that the Rb gene may act as a 'status quo' cellular growth fraction control mechanism. In reactive lymphoid tissue, Rb protein was mainly expressed in germinal centres (lymph nodes, tonsils) and cortical thymocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

The expression of p53 protein in non-Hodgkin's lymphomas is not always dependent on p53 gene mutations.

p53 overexpression has been found to be a fairly common feature in high grade lymphomas in the majority of tumoral cells. The results vary from series to series, from 25% to 33% of cases. To assess whether immunohistochemical positivity for p53 correlated with the presence of structural gene abnormalities, DNA from 16 non-Hodgkin's lymphomas with high and low p53 values was amplified and sequenced to determine the existence of point mutations in the highly conserved regions of the p53 gene. In the group of 8 cases containing high levels of protein, 3 cases showed missense point mutations at the codons mapping between exons 5 through 8. Of the 8 cases of tumors containing undetectable or low levels of p53 protein, 1 case presented a nonsense point mutation giving a stop codon. No missense mutations were detected in this group. The finding of p53 mutations in 4 of 16 cases confirms the presence of p53 gene mutations in high grade lymphomas distributed over different histologic groups. These include Burkitt's lymphoma, together with centroblastic, immunoblastic, and large cell lymphoma of mucosa origin. Nevertheless, the absence of mutations in 5 of the 8 cases that overexpressed p53 suggests that the nuclear or cytoplasmic stabilization of p53 protein could also depend on other factors. The absence of detectable levels of p53 protein cannot discount the existence of p53 mutations, as is shown by a case of Burkitt's lymphoma in which a nonsense mutation was detected. The impact of this range of p53 alterations on clinical course and treatment response of the patients deserves to be explored, in an attempt to differentiate the specific consequences of each one.