[Pathologic diagnosis of mantle cell lymphoma based on histologic, cytologic, immunohistologic and genetic characteristics]

Mantle cell lymphoma (MCL) is a clinocopathologic entity representing a broad histologic and cytologic spectrum from cystic to the blastic form. The histologic, cytologic heterogeneity of MCLs may lead to diagnostic confusion. The aim of this study was to reclassify NHLs registered as centrocytic lymphoma and centrocytoid-centroblastoma by the Lymphoma Reference Centrum at the Department of Pathology, University Medical School of Pécs between 1988 and 1995. 63 of 67 selected cases have been classified as mantle cell lymphoma according to histological, cytological appearance, and the pheno- and genotype of tumour cells. 48% of the cases showed diffuse while 52% showed nodular histological pattern. 27% of diffuse MCLs composed of classic MCL cells (small to medium-size cells) 40% blastic and 33% both small and blastic lymphoma cells. In 76% of the nodular MCLs the tumour consisted of small to medium-size cells 15% blastic while 9% both small and blastic lymphoma cells. In 99% of MCL the diagnosis was supported by CD5, CD20 and CD23 positivity and in 67% by the presence of cyclin D1-overexpression. The t(11;14) chromosome translocation PCR amplification was positive in 3 of 17 cases investigated. The authors conclude that MCLs represent a heterogeneous disease based on the cytology of the tumour cells. The nodular architecture was associated with classic MCL cells while the diffuse form was more frequently associated with blastic or combined cytological appearance. The correct diagnosis of MCL could be reached by tumour cell immunophenotyping, while molecular genetic methods proved to be informative only in part of the cases studied.

[Analysis of T-cell receptor gamma-gene rearrangement in lymphoproliferative disorders using polymerase chain reaction]

T-cell non-Hodgkin's lymphomas (NHL) exhibit a clonal T-cell receptor (TCR) gamma gene rearrangement as a result of sequential assembly of their variable (V gamma) and joining (J gamma) region segments. The analysis of the TCR gamma gene rearrangements may help to differentiate reactive lymphoproliferations from T-cell NHLs. The aim of this study was to reveal the usefulness of polymerase chain reaction (PCR) analysis of the TCR gamma gene rearrangement in the diagnosis of T-cell NHLs using native and formol-paraffin embedded tissues. The PCR amplification of the TCR gamma gene was performed by the V gamma specific sense and J gamma specific antisense primer pairs. The PCR products were evaluated by polyacrilamide gel electrophoresis containing ethidium bromide. The PCR analysis of the TCR gamma gene rearrangements has been performed in 95 lymphoproliferative disorders. The PCR analysis of the TCR gamma gene showed clonal gene rearrangement in 22 cases out of the 39 T-cell NHLs and in one case out of the 12 O-cell anaplastic large cell lymphoma but no clonal rearrangements were detected in any of the 15 reactive lymphoproliferations or 13 B-cell NHLs. Thus, clonal TCR gamma gene rearrangements was detected by PCR in 58.2% of T-cell NHLs but no clonal TCR gamma gene rearrangements were shown in any of reactive lymphoproliferations of B-cell NHLs. These studied showed that the PCR amplification of the TCR gamma gene can be a powerful tool in the diagnosis of T-cell NHLs.

Blastic transformation of mantle cell lymphoma: genetic evidence for a clonal link between the two stages of the tumour

AIMS

The blastic variant of mantle cell lymphoma (MCL-BV) may develop through histological transformation of mantle cell lymphoma (MCL). However, the clonal link between the tumour cells of MCL and transformed MCL-BV has not been established at the genetic level. To investigate this link longitudinal molecular genetic studies have been performed in two cases of MCL that showed morphological transformation to MCL-BV.

METHODS AND RESULTS

Polymerase chain reaction (PCR) and nucleotide sequence analyses of the complementary determining region 3 (CDR) of the immunoglobulin (Ig) heavy chain (H) gene were performed to identify clone-specific rearrangements. In both cases, nucleotide sequence analysis revealed common clone-specific IgH gene rearrangements in MCL and subsequent MCL-BV.

CONCLUSIONS

These results provide genetic evidence for the common clonal origin of MCL and subsequently developed MCL-BV.

Primary effusional lymphoma: A new non-Hodgkin s lymphoma entity

A distinct non-Hodgkin s lymphoma (NHL) entity that grow in the body cavities as lymphomatous effusions in the absence of clinically identifiable tumor masses has been defined as primary effusional lymphoma (PEL). This lymphoma characterized by distinetive morphology, immunophenotype, genotype and association with Kaposi s sarcoma-associated herpesvirus (KHSV)/human herpesvirus-8 (HHV-8) infection. In this minireview, the clinico-pathological and biological characteristics of PELs are summarized.

High-grade transformation of low-grade non-Hodgkin's lymphomas: mechanisms of tumor progression

In the natural history of low-grade non-Hodgkin's lymphomas (NHL) a prolonged indolent phase of the disease may be followed by clinical progression toward intermediate and high-grade disease. The abrupt appearance of diffuse large cell lymphoma (DLL) in patients with low-grade NHL is usually associated with an accelerated clinical course and shorter time of survival. The histologic transformation has been described for chronic lymphocytic leukemia or small lymphocytic lymphoma (CLL/SLL), follicular lymphoma (FL), mantle cell lymphoma (MCL) and lymphoma of mucosa-associated lymphoid tissue (MALT). Although the histological transformation of low-grade lymphomas are relatively frequent, the clonal relationship between the two neoplasms and pathogenetic mechanisms underlying the progression of the disease are widely debated. In this review, we will focus on the possible relationship between the low-grade and the transformed high-grade NHLs and genetic lesions that may be associated with the histologic transformation and clinical progression of the disease.

Syndecan-1 (CD138) expression in human non-Hodgkin lymphomas

Syndecan-1, an important transmembrane heparan sulphate proteoglycan is expressed in distinct stages of differentiation of normal lymphoid cells: in pre-B cells and Ig-producing plasma cells; however, its normal function, or presence in lymphoid malignancies, is still largely unknown. The expression of syndecan-1 (CD138) was studied in 57 human non-Hodgkin lymphomas using immunocytochemistry and immunohistochemistry. Positive expression of syndecan-1 was found in the plasma cells in chronic lymphoblastic leukaemia (B-CLL) cases, in different plasmocytoid lymphomas as well as in myeloma. All normal and malignant Tcells, or CD5+ cells other than B-CLL proved to be negative. These results strongly suggest that syndecan-1 expression is a characteristic phenotypic marker for B-CLL and lymphoplasmocytoid lymphomas and could be used for diagnostic purposes.

Distinct clonal origin of low-grade MALT-type and high-grade lesions of a multifocal gastric lymphoma

AIMS

Low-grade mucosa-associated lymphoid tissue (MALT) lymphoma and high-grade B-cell non-Hodgkin's lymphoma (NHL) of the stomach may occur simultaneously. To determine the clonal relationship between these tumours, we compared the immunoglobulin heavy chain gene (IgH) rearrangements of low and high-grade components of a multifocal gastric NHL.

METHODS AND RESULTS

The complementary determining region 3 (CDR3) of the IgH gene rearrangements were polymerase chain reaction (PCR) amplified, cloned and sequenced. The analysis of the CDR3 sequences rearranged by tumour cells of low-grade MALT and the high-grade NHL revealed different nucleic acid sequences.

CONCLUSION

These findings suggest that low-grade MALT and high-grade B-cell components of multifocal gastric NHL may represent unrelated clones.

Immunoglobulin VH gene mutational analysis suggests that primary effusion lymphomas derive from different stages of B cell maturation

Primary effusion lymphoma (PEL) is a recently described distinct subtype of non-Hodgkin's lymphoma associated with infection by the Kaposi's sarcoma-associated herpesvirus, also called human herpesvirus-8. Most cases of PEL are also associated with the Epstein-Barr virus (EBV). In order to better characterize the cellular origin of PEL, we investigated the immunoglobulin (Ig) heavy chain variable region (VH,) genes expressed by tumor cells of the BC-1 and BC-3 cell lines derived from PELs and five original PEL specimens. In the six EBV-positive PELs examined, including the BC-1 cell line, the expressed VH gene sequences showed numerous point mutations relative to the putative germline VH gene sequences. In addition, the VH, segment of one of these cases showed intraclonal sequence heterogeneity, indicating ongoing somatic mutation. In five cases, the distribution and type of mutations indicated that tumor cells had been selected by antigen. Because somatically mutated Ig genes are expressed by B cells that have reached a germinal center/post-germinal center stage of development, these findings suggest that the PEL cell of origin is a germinal center or post-germinal center B cell in most cases. In contrast, the VH gene segment expressed by tumor cells of the BC-3 cell line, which was originated from an EBV-negative PEL obtained from an HIV-negative patient, was unmutated, suggesting a pre-germinal center B cell origin for tumor cells of this particular PEL cell line. Taken together, these findings suggest that development of PELs may not be restricted to one stage of B cell differentiation and may represent transformation of B cells at different stages of ontogeny.

In vivo effects of CHOP protocol on onco and suppressor gene expression: follow-up study

In vivo investigation of onco/suppressor gene effects may provide new findings concerning chemical carcinogenesis. In earlier studies we pointed out the carcinogenic potential of COPP and ABVD chemotherapeutical protocols in "long-term" experiments. In another follow up study we proved the connection between the early gene expression changes and the late consequences of COPP and ABVD treatment during, a one year latency period. CHOP protocol is containing both proved carcinogenic cyclophosphamide and highly mutagenic doxorubicyn. CHOP protocol in "short-term" experiments shows strong effect on Ha-ras oncogene expression.

Phenotypic and genotypic analyses of blastic cell population suggest that pure B-lymphoblastic leukemia may arise from myelodysplastic syndrome

The case history of a 70-year-old man with myelodysplastic syndrome terminated into acute leukemia in 22 months is presented. The leukemic cells exhibited multifocal acid phosphatase positivity and expressed TdT, CD45, CD34 and HLA-DR but not myeloid, monocytic or megakaryocytic differentiation antigenes. The genotypic analysis revealed clonal immunoglobulin heavy chain gene rearrangement. These phenotypic and genotypic analyses of the blastic cell population suggest that myelodysplastic syndrome may transform to pure acute lymphoblastic leukemia of B-cell origin.

[The presence of t(14;18) chromosome translocation in various types of diseases]

Chromosome translocation of t(14;18) can be detected in most cases of centroblastic/centrocytic follicular lymphomas. They are causative factors of lymphomas but the translocation is present in different other types of diseases although the translocation does not belong to the features of these illnesses. Our present work shows the appearance of t(14;18) translocation in lymphocytes of two patients of Sjögren's syndrome, one that of Whipple disease as well as one of healthy donors' lymphocytes using polymerase chain reaction technique presented in one of our previous publication. The translocation occurred in the mbr of bcl-2 gene in all cases showed and the bcl-2 gene was coupled with the immunoglobulin heavy chain gene. These results are definitively positive concerning the fact of translocation as it has been proved by sequencing of the amplification products showed in our earlier and present paper. Because relatively high percentages of Sjögren's syndrome patients develop later on lymphoma, the early detection of the translocation could result in a more successful diagnosis as well as treatment of the disease. The question arises, however, what role the translocation plays in illnesses such as the Whipple disease or what kind of consequences can be drawn from the appearance of the t(14;18) translocation in lymphocytes of healthy donors.

[The role of genetic studies in the diagnosis and classification of non-Hodgkin lymphoma]

The revised European-American Classification of Lymphoid Neoplasms (REAL), proposed by the International Lymphoma Study Group, contains molecular genetic data which may characterize a given lymphoma entity. In this recent review, the molecular genetic alterations integrated into the diagnostic procedure of lymphomas are discussed. Based on our recent knowledge the rearrangements of bcl-1, bcl-2, bcl-6, anaplastic lymphoma kinase and c-myc genes are associated with mantle cell, diffuse large B-cell, anaplastic large cell and Burkitt's lymphomas, respectively. The integration of the relevant molecular data in the evaluation of objective diagnoses and therefore specific and successful therapies. Furthermore, the knowledge of the molecular event associated with lymphomas helps to better understand tumor development and biology.

[A case of myelodysplastic syndrome transforming into acute B-cell lymphoid leukemia]

Case history of a seventy year old man with myelodysplastic syndrome is presented. The disease terminated into acute leukaemia in 22 months. The pure, B lymphoid stem cell nature of the leukaemic cells has been proved, beside morphology and cytochemistry, by detailed flow cytometric phenotyping and PCR amplification as well as sequencing of the immunoglobulin heavy chain gene CDR3 region.

[Detection of t(14;18) chromosome translocation in follicular lymphoma by polymerase chain reaction]

In most cases of centroblastic/centrocytic follicular lymphomas the bcl-2 proto-oncogene (18q21) is translocated to the immunoglobulin JH region of chromosome 14 (14q32). About three quarters of the translocations are concentrated on the 3' nontranslated, a few hundred basepare-long region of bcl-2, the so called major breakpoint region (mbr), the remaining 20-25% is located about 30 kilobases downstream of bcl-2 coding sequences in the minor cluster region (mcr). The majority of the immunoglobulin breakpoints can be found in JH6-4 genes. The polymerase chain reaction method can detect the translocation already in a very few number of cells (> 10(3)). This very sensitive technique makes it possible to detect the translocation in lymphoid/lymphoma of peripheral blood and bone marrow that are missed by other diagnostic methods. This way one can perform a quick, early diagnosis, examine the result of treatments as well as detect the remissions and the possible relapses right at the beginning. All the advantages of this method contribute to a more successful treatment of follicular lymphoma. This present work describes a polymerase chain reaction technique which is capable of a detection of the t(14;18) translocation in a patient of centroblastic/centrocytic lymphoma, moreover shows how this translocation disappears after 4 week of radiotherapy of the patient.

Molecular characterization of IgA- and/or IgG-switched chronic lymphocytic leukemia B cells

The immunoglobulin (Ig) variable region (V) genes expressed by IgM chronic lymphocytic leukemia (CLL) B cells display little or no somatic mutations. However, preliminary findings have shown that Ig V genes of IgA and IgG CLLs may be somatically mutated, suggesting that isotype-switched CLLs may represent a "subtype" of the disease. To investigate the degree and nature of somatic mutations and the role of antigen (Ag) in the clonal selection and expansion of isotype-switched CLLs, and to determine whether specific oncogene or tumor suppressor gene mutations are associated with isotype-switched CLLs, we analyzed the expressed Ig VH gene, bcl-1 and bcl-2 proto-oncogene, and p53 tumor suppressor gene configurations of 3 IgA-, 1 IgG-, and 1 IgA/ IgG-expressing CLLs. These isotype-switched CLL B cells expressed surface HLA-DR, CD19, CD23, and CD5, and displayed no alterations of the bcl-1 and bcl-2 oncogenes and the p53 tumor-suppressor gene. The cDNA VH-D-JH gene sequence was joined with that of the C alpha gene in the B cells of the three IgA CLLs, and with that of the C gamma gene in the IgG CLL B cells. In the IgA/IgG-coexpressing CLL B cells, identical VH-D-JH cDNA sequences were spliced to either C alpha or C gamma genes. In all five CLLs, the pattern of C mu DNA probe hybridization to the digested genomic DNAs was consistent with deletion of the C mu exon from the rearranged Ig gene locus, suggesting that these CLL B cells had undergone DNA switch recombination. In one IgA CLL, the expressed VH gene was unmutated. In all other class-switched CLLs, the Ig VH segment gene was mutated, but the point mutations were not associated with intraclonal diversification. In one IgA and in the IgA/IgG-coexpressing CLL, the nature and distribution of the mutations were consistent with Ag selection. These findings suggest that IgA- and/or IgG-expressing CLLs represent, in their VH gene structure, transformants of B cells at different stages of ontogeny. They also suggest that Ag may play a role in the clonal selection of some of these isotype-switched leukemic cells, but bcl-1 and bcl-2 oncogene rearrangements and p53 tumor suppressor gene mutation are not associated with the pathogenesis of isotype-switched CLLs.

Somatic mutations of the translocated bcl-2 gene are associated with morphologic transformation of follicular lymphoma to diffuse large-cell lymphoma

BACKGROUND

Ninety percent of low-grade follicular lymphomas (FLs) carry the t(14;18) translocation. This event juxtaposes the bcl-2 oncogene to the immunoglobulin (Ig) heavy-chain gene and leads to bcl-2 gene overexpression. Morphologic transformation of FL to high-grade lymphoma is associated with multiple secondary chromosomal abnormalities of the neoplastic cells.

DESIGN

To analyze whether additional structural alterations of the translocated bcl-2 gene are associated with morphologic transformation of FL, we PCR-amplified, cloned, and sequenced the major breakpoint region (MBR) and the open reading frames (ORF) of the translocated bcl-2 oncogene in six paired samples of FL and subsequent diffuse large-cell lymphoma (DLL).

RESULTS

In five cases, FL and DLL cells were clonally related, as suggested by the identical MBR sequences, but in one case they were different. PCR single-strand conformation polymorphism (SSCP) and sequence analyses were performed for identification of structural alterations of the bcl-2 gene in the OFR region corresponding to the 239 amino acid p26-bcl-2a protein. In three of the six patients, a total of 11 point mutations of the ORF were detected in the DLL cells. Four of them, at positions 29, 46, 59, and 106, yielded amino acid replacements.

CONCLUSIONS

These findings demonstrate that FL and DLL cells may be clonally related or unrelated. They also show that transformation of FL cells can be associated with somatic point mutations of the bcl-2 oncogene ORF sequence resulting in alteration of the p26-bcl-2a gene product.

Morphologic transformation of follicular lymphoma is associated with somatic mutation of the translocated Bcl-2 gene

Follicular lymphoma (FL) is a low-grade B-cell non-Hodgkin's lymphoma (NHL) that frequently transforms into diffuse aggressive NHL. The majority of FLs display a t(14; 18) translocation that places the bcl-2 gene into juxtaposition with the lg heavy-chain (H) gene locus. Morphologically transformed malignant FL cells retain their t(14;18) translocation and may acquire additional genetic abnormalities. We analyzed serial biopsy specimens from eight patients with FL for secondary alterations of the rearranged bcl-2 gene in the breakpoint and open reading frame (ORF) regions. Two cases of FL showed no histologic alteration in the second biopsy, and six cases of FL showed morphologic transformation to diffuse large-cell lymphoma (DLL) in the second biopsy. Polymerase chain reaction (PCR) amplification, cloning, and sequencing of the junctional region of the hybrid bcl-2/IgH genes showed identical nucleotide sequences in multiple biopsy specimens of FL that did not show morphologic transformation. In patients in whom FL cells underwent morphologic transformation, FL and autologous DLL cells displayed identical bcl-2/IgH gene nucleotide sequences in five cases and different sequences in one case. In the case for which FL and DLL cells showed different bcl-2/IgH junctional sequences, DLL cells incorporated larger bcl-2 and Ig-joining (JH) gene fragments than the corresponding FL cells, suggesting that DLL clones developed by a distinct t(14; 18) translocation rather than by alteration of the hybrid bcl-2/IgH gene detected in the FL cells. In all eight cases, neither FL nor DLL cells showed alterations of bcl-2 gene sequences in the breakpoint region, suggesting high conservation of the bcl-2 gene during both t(14; 18) translocation and morphologic transformation of the FL cells. PCR single-strand conformation polymorphism (SSCP) and sequence analyses were performed for identification of structural alterations of the bcl-2 gene in the ORF region corresponding to the 239-amino acid p26-bcl-2 alpha protein. A total of 11 point mutations of the ORF were detected in DLL cells of three transformed NHLs, but no alteration of the ORF was detected in FL cells. Four of 11 mutations, at positions 29, 46, 59, and 106, yielded amino acid replacements. These findings demonstrate that FL and DLL cells may be clonally related or unrelated. They also show that transformation of FL cells may be associated with somatic point mutations of the bcl-2 proto-oncogene ORF sequence resulting in alteration of the p26-bcl-2 alpha gene product.

[Clonality analysis of B-cell lymphoproliferative disorders by means of immunoglobulin heavy chain polymerase reaction]

The majority of B-cell non-Hodgkin's lymphomas (NHL) exhibit a highly specific immunoglobulin heavy chain (IgH) gene rearrangement as a result of sequential assembly of their Ig variable (VH), diversity (D) and joining (JH) region segments. The analyses of Ig gene rearrangements in B cells may help to differentiate reactive lymphoproliferations from NHLs, and to identify of their B-cell origin. The aim of this study was to reveal the usefulness of polymerase chain reaction analysis of the Ig gene rearrangement in the diagnosis of B-cell NHLs, using native and formol-paraffin embedded samples. The authors analysed 67 biopsy samples of immunohistochemically characterized lymph nodes diagnosed at the Department of Pathology. University Medical School of Pécs, between 1993 and 1995, using IgH gene polymerase chain reaction. The 67 samples included 10 reactive lymphoproliferations, 47 B-cell, 5 T-cell NHLs and 5 Hodgkin's diseases. In 54 cases, fresh, unfixed, in 13 cases, formalin-fixed samples have been used. The polymerase chain reaction amplification of the Ig heavy chain third complementary determining region (CDR 3) was performed by IgVH specific sense and JH specific antisense primer pairs. The polymerase chain reaction products were evaluated by agarose gel electrophoresis containing ethidium bromide. Sixty-four % of fresh, unfixed and 54% of formol-paraffin fixed B-cell NHLs samples showed clonal Ig gene rearrangement. The applied polymerase chain reaction technique did not show clonal amplification in reactive lymphoproliferations, T-cell NHLs or Hodgkin's disease. The polymerase chain reaction amplification of the IgH gene can be a powerful tool in the diagnosis of monoclonal B-cell lymphoproliferative disorders.

Different clonal origin of B-cell populations of chronic lymphocytic leukemia and large-cell lymphoma in Richter's syndrome

Richter's syndrome is defined as the morphologic transformation of chronic lymphocytic leukemia (CLL) into diffuse large-cell lymphoma (DLL). To determine the clonal nature of the two malignancies, we microdissected the CLL and DLL cells from a lymph node of Richter's syndrome and analyzed the sequences of the rearranged Ig VH-D-JH genes of the two lymphomas. Using the Ig VH-D-JH sequence as a marker of clonality, we delineated the clonal relationship of the CLL and DLL cells. The microdissected CLL and DLL cells productively rearranged different VH, D, and JH genes, suggesting that these DLL B cells emerge as discrete elements independent of the CLL B-cell population. The productively rearranged Ig V gene sequence of the CLL clone was 100% identical to the VH6 germline gene, but the rearranged Ig VH gene of the DLL clone was somatically point-mutated based on comparison of its sequence with those of reported germline genes. In the DLL clone, the random distribution and nature of the somatic point-mutations suggests a lack of antigen selection; the identity of the somatic point-mutations in multiple independent isolates of the same B-cell clone suggests a lack of intraclonal diversity. Thus, Richter's syndrome DLL B cells are monoclonal and can emerge as discrete elements independent of the preexisting CLL cells; antigen selection and clonal diversification are not necessarily associated with the events leading to this aggressive neoplastic transformation.

De novo CD5-positive and Richter's syndrome-associated diffuse large B cell lymphomas are genotypically distinct

Diffuse large B cell lymphomas (DLBLs) represent a heterogeneous collection of aggressive non-Hodgkin's lymphomas that can arise either de novo or as a result of transformation from chronic lymphocytic leukemia, small lymphocytic lymphoma, follicular lymphomas, or lymphomas of mucosa-associated lymphoid tissue. A small percentage of DLBLs express the CD5 antigen. The majority of these cases have evolved from a pre-existing low grade non-Hodgkin's lymphoma (Richter's syndrome). However, we identified and characterized nine CD5-positive DLBLs in which the patients did not have a previous history or concomitant evidence of chronic lymphocytic leukemia, small lymphocytic lymphoma, follicular lymphoma, or mucosa-associated lymphoid tissue-associated non-Hodgkin's lymphoma, suggesting that they arose de novo. All nine cases expressed CD20 and monotypic immunoglobulin, all eight cases examined expressed CD19, CD22 and CD43, eight of the nine cases expressed HLA-DR, and two of eight cases expressed CD11c. None of the cases expressed CD3, CD10, CD11b, CD21, CD23 or CD30. CD5 expression by these cells was found to be identical to that of CD5-positive B cell chronic lymphocytic leukemia by quantitative polymerase chain reaction analysis of CD5 mRNA. These nine de novo CD5-positive DLBLs exhibited clonal immunoglobulin heavy and light chain gene rearrangements but lacked integration of the Epstein-Barr virus genome and structural alterations of the bcl-1, bcl-2, c-myc, H-ras, K-ras, and N-ras proto-oncogenes and the p53 tumor suppressor gene. However, bcl-6 proto-oncogene rearrangement, which is involved in chromosome band 3q27 aberrations, was found in four cases (44.4%). This is comparable with the frequency of bcl-6 gene rearrangement in CD5-negative DLBL. In contrast, bcl-6 gene rearrangement was absent in six cases of DLBL associated with Richter's syndrome. These findings suggest that de novo CD5-positive DLBLs are genotypically similar to CD5-negative DLBLs and may be pathogenetically distinct from the DLBLs associated with Richter's syndrome.

Molecular genetic demonstration of the diverse evolution of Richter's syndrome (chronic lymphocytic leukemia and subsequent large cell lymphoma)

Paired samples of chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) and the subsequent diffuse large cell lymphoma (DLL) of six cases of Richter's syndrome were investigated to establish the clonal relationship between the CLL/SLL and the DLL components and to define the oncogene and/or tumor-suppressor gene alterations involved in the morphologic transformation of CLL/SLL. Southern blot hybridization analysis showed identical clonal immunoglobulin (Ig) gene-rearrangement patterns in the CLL/SLL and DLL components in four cases and different Ig gene-rearrangement patterns in two cases. Polymerase chain reaction (PCR) amplification, cloning, and DNA sequencing of complementary determinant region 3 (CDR3) of the Ig-heavy chain gene of one of the two cases in which the Ig gene-rearrangement patterns were different showed nonidentical sequences in the CLL/SLL and DLL components. In the other case, monomorphic Epstein-Barr virus (EBV) genome integration was detected in the DLL but not in the CLL, suggesting that the CLL and DLL components in this case of Richter's syndrome also represent unrelated clones. Single-strand conformation polymorphism (SSCP) analysis and sequencing of exons 5 through 9 of the p53 tumor-suppressor gene showed a mutation in codon 176 of the DLL but not in the CLL/SLL component in one case where the CLL/SLL and DLL represented different clones. The p53 mutation probably played a role in the development of the lymphoma rather than morphologic transformation of the CLL/SLL in this case. SSCP analysis and sequencing also showed identical mutations in codon 282 in both the CLL/SLL and DLL components in a case where the CLL and DLL represented identical clones. Thus, this p53 gene mutation was present both before and after morphologic transformation, and therefore, probably did not play a primary role in this process. Southern blot hybridization analysis failed to show evidence of bcl-1, bcl-2, c-myc proto-oncogene or retinoblastoma (Rb) tumor-suppressor gene rearrangements in these six cases of Richter's syndrome. In conclusion, the original CLL/SLL and the subsequent DLL in Richter's syndrome may or may not be derived from identical clones, and the well-known proto-oncogenes and tumor-suppressor genes do not appear to play an obvious and consistent role in the morphologic transformation of CLL/SLL to DLL.

Nucleolar organizer regions of megakaryocytes in chronic myeloproliferative disorders

To study megakaryocyte activation, the argyrophilic staining method of nucleolar organizer regions (AgNOR) has been applied to decalcified bone marrow biopsies of 16 individuals with no haematopoietic disorders and 59 patients with chronic myeloproliferative disease. Of the 59 patients, 18 had chronic myeloid leukaemia (CML), 21 chronic megakaryocytic granulocytic myelosis (CMGM), 13 polycythaemia vera (PV) and 7 essential thrombocythaemia (ET). The AgNOR number of megakaryocytes in CML was significantly lower, and in CMGM, PV and ET significantly higher than in healthy individuals. The high number and the clusters of fine-grained AgNORs of megakaryocytes in CMGM, PV and ET are suggestive of active, proliferating cells. The AgNOR number of megakaryocytes and the platelet counts of the patients did not show a convincing correlation. In CMGM, PV and ET the pyknotic, heterochromatinized megakaryocytes with narrow rims of cytoplasm called bare (nude) nuclei, possessed few, large AgNOR granules. The AgNOR staining of bare nuclei and the roughly identical number of granules found in CMGM, PV and ET indicate a common, active mechanism of apoptosis.

[Diagnosis of chronic myeloproliferative diseases based on bone marrow biopsy]

The bone marrow biopsies and laboratory data of 248 patients with untreated chronic myeloproliferative disorders have been evaluated according to the Hannover Classification. 47.6 per cent of the cases were classed as primary or basic diseases, including chronic myeloid leukaemia common type, chronic myeloid leukaemia megakaryocytic type, chronic megakaryocytic-granulocytic myelosis, polycythaemia vera and essential thrombocythaemia. In 52.4 per cent of the biopsies the advanced stages of the primary diseases like increase of fibers and loss of differentiation were noted; the increase of fibers in myeloid leukaemia megakaryocytic type and in chronic megakaryocytic-granulocytic myelosis, and loss of differentiation in chronic myeloid leukaemia common type were frequently noted. In 14.1 per cent of the cases the advanced myelofibrosis and blast cell accumulations obscured the histological features of the primary disease, therefore these cases were placed in the unclassifiable group. The cases without increase of fibers and loss of differentiation accounted for only 4 per cent of the unclassifiable category. Leucocyte and platelet count as well as haematocrit values showed considerable overlapping and scattering and were generally lower in cases which developed myelofibrosis.