Benign and malignant lymphoid lesions of the stomach. A histological reappraisal in the light of the Kiel classification for non-Hodgkin''s lymphomas

Twenty-two cases of lymphoid tumours of the stomach were reviewed by application of the Kiel classification for non-Hodgkin's malignant lymphomas. Four cases of pseudolymphomas were found, one of which had been previously misdiagnosed as malignant lymphoma. The remaining cases were all malignant tumours with B-cell lymphoma features. These were divided into seven low grade lymphomas (three immunocytomas and four centroblastic/centrocytic) and II high grade lymphomas (six centroblastic and five immunoblastic lymphomas). No cases of Hodgkin's disease or lymphoblastic lymphoma were observed. The Kiel nomenclature was not only easy to apply, but also helped to differentiate pseudolymphoma from malignant lymphoma. Both the pseudolymphomas and the malignant lymphomas were consistently associated with follicular gastritis. This lesion, while intrinsically non specific, was sometimes accompanied by suggestions of transition between itself and the lymphoma, a fact which at least raises the possibility of a transformation of the former into the latter.     

Ploidy, proliferative activity, cluster differentiation antigen expression and clinical remission in highgrade non-Hodgkin''s lymphoma

Using a large range of monoclonal antibodies to specific cluster differentiation antigens the phenotypes of a series of high-grade non-Hodgkin's lymphomas of B- and T-cell type were investigated. Cell ploidy and proliferative fraction were assessed by fluorescent staining of DNA and flow cytometry and data on the incidence of complete clinical remission were obtained. With the exception of some lymphoblastic lymphomas, high-grade B-cell lymphomas normally expressed the pan B-cell antigens CD19 and CD22 but only immunoblastic lymphomas consistently expressed the pan B marker CD20. Variable, generally weak expression of CD21 was observed whilst CD23 expression was most prevalent in rapidly proliferative cases and in Burkitt's and centroblastic lymphomas. A rapidly proliferative, multilobated B-cell lymphoma displayed phenotypic properties intermediate between centroblastic and immunoblastic lymphomas. The T-cell lymphomas generally showed low proliferative activity and expression of CD4 prevailed over CD8. Most cases also showed CD2 and CD5 positivity with some also showing CD3 and CD7 expression. Patients with rapidly proliferative diploid or DNA aneuploid tumours obtained complete remission more readily than patients with lowly proliferative diploid tumours. An excess of early deaths occurred among T-cell cases.     

C-MYC rearrangements are frequent in aggressive mature B-Cell lymphoma with atypical morphology

Diagnosis and classification of aggressive mature B-cell lymphoma with atypical morphology remains a challenge. To identify factors that may contribute to the atypical morphology, we selected eight such cases and evaluated their morphologic, immunophenotypic and cytogenetic features and clinical outcomes. The neoplastic cells showed a diffuse monotonous infiltrating pattern with a spectrum of morphology including: 1) L1 lymphoblastic; 2) centroblastic; 3) immunoblastic; and 4) mixed centroblastic and immunoblastic. The lymphoma cells in most cases were positive for CD10 and/or BCL6, and showed BCL2 expression. 6 of 8 cases showed C-MYC rearrangements, and interestingly, all 6 cases demonstrated a proliferation index of < or =90%. 3 of the 6 cases also demonstrated t(14;18). Clinical follow-up indicated that aggressive mature B-cell lymphoma may benefit from more intensified chemotherapeutic regimens used for BL. Our study suggests that aggressive mature B-cell lymphoma with atypical morphology may be another "grey zone lymphoma" lying in the spectrum between Burkitt lymphoma and diffuse large B-cell lymphoma.     

Gene rearrangement of bcl-1 and bcl-2 is confined to distinct subgroups of high-grade malignant B-cell lymphomas

The occurrence of bcl-1 and bcl-2 gene rearrangements was investigated in 37 cases of high-grade B-cell lymphomas. Bcl-2 rearrangement was detectable only in single cases of primary centroblastic lymphoma with a follicular growth pattern, whereas secondary centroblastic lymphomas evolving from a centroblastic–centrocytic lymphoma were positive in up to 60 per cent of the cases analysed. Bcl-1 rearrangement was found only in one case of immunoblastic B-cell lymphoma with a history of a pre-existing lymphoplasmacytoid immunocytoma. It is concluded that there may be a subgroup of centroblastic lymphomas with a biology similar to that of centroblastic–centrocytic lymphomas. The detection of bcl-1 rearrangement in high-grade lymphomas may indicate a secondary high-grade lymphoma.     

Primary non-Hodgkin's lymphoma of the intestine: a morphological, immunohistochemical and clinical study of 31 Chinese cases

Thirty-one cases of primary non-Hodgkin's lymphoma of the intestine were investigated. Twenty-one were of B-cell and 10 of T-cell origin. The B-cell lymphomas comprised two cases of low-grade B-cell lymphoma of mucosaassociated lymphoid tissue (MALT), one of centroblastic/centrocytic type, three of high-grade B-cell lymphoma coexisting with a low-grade B-cell lymphoma of MALT, nine of centroblastic, three of immunoblastic and three of Burkitt type. Of the T-cell lymphomas, eight were of pleomorphic medium-to large-sized cell type and two of large cell anaplastic type. All the B-cell lymphomas expressed CD20 (L26) and/or Ki-B5; in six there was monotypic immunoglobulin light chain restriction. Membrane positivity for CD45RO (UCHL1) was observed in the 10 cases of T-cell lymphoma, but the tumour cells did not express monocyte-macrophage markers. Clinically, the patients with T-cell lymphomas were usually young males with constitutional symptoms and their prognosis was significantly worse than those of patients with intestinal B-cell lymphoma.     

Follicular dendritic cells in extranodal non-Hodgkin lymphomas of MALT and non-MALT type

Extranodal lymphomas of the thyroid (n=19), kidney (n=15) and testis (n=30) were investigated histologically and immunohistochemically for follicular dendritic cell pattern using the monoclonal antibody Ki-FDC1P. This recognizes follicular dendritic cells in paraffin sections. Follicular dendritic cells were most predominant in lymphomas of the thyroid. These thyroid lymphomas showed the morphological features of mucosa-associated lymphoid tissue (MALT) type lymphomas in 18 of 19 cases and were classified as high-grade malignant lymphoma of MALT type with evidence of a low-grade malignant component (n=18). Ten of these cases contained destroyed reactive follicles of follicular dendritic cells. In 6 of these 10 cases follicular dendritic cells occurred in a pattern of tumour-associated abortive follicle type. The remaining lymphoma of the thyroid was an immunoblastic lymphoma of B-cell type showing no detectable follicular dendritic cells. In extranodal lymphomas of non-MALT type follicular dendritic cells occurred in only two cases where immunocytoma involved the kidney. Malignant lymphomas of the kidney (chronic lymphocytic leukaemia,n=2; immunocytoma,n=4; centroblastic lymphoma,n=9) and of the testis (immunocytoma,n=2; centroblastic lymphoma,n=27; immunoblastic lymphoma of B-cell type,n=1) revealed no characteristics of MALT type lymphoma, cytologically or with respect to follicular dendritic cells. Classical lymphoepithelial lesions formed by centrocyte-like cells, a hallmark of MALT, occurred exclusively in thyroid lymphomas of MALT type. Although occurrence of classical lymphoepithelial lesions formed by centrocyte-like cells was limited to thyroid lymphomas of MALT type, a growth pattern of lymphoid blasts, with formation of lesions mimicking lymphoepithelial lesions superficially, was found in 6 of 27 testicular centroblastic lymphomas. Follicular dendritic cells in non-Hodgkin's lymphomas of MALT type show distinct follicular patterns not found in other extranodal lymphomas such as those found in the kidney and testis.     

B-cell non-Hodgkin lymphomas in Uganda: an immunohistochemical appraisal on tissue microarray

The most common non-Hodgkin lymphomas in Uganda are neoplasms of B-cell derivation. The field of B-cell lymphoma immunophenotype has rapidly progressed because of the increasing availability of markers applicable to routine sections. Although the latter have allowed the identification of distinctive lymphoma entities in the developed countries, such approach has not yet been used in Uganda. One hundred twenty-nine formalin-fixed, paraffin-embedded tissue samples from the Department of Pathology of Makerere University were used for tissue micro-array (TMA) construction. Four-micrometer-thick sections were cut from TMAs and stained with hematoxylin and eosin and Giemsa. They were also used for immunohistochemistry and in situ hybridization. According to morphology and immunohistochemistry, lymphoid neoplasms were classified as Burkitt's lymphoma (BL) (95 cases), diffuse large B-cell lymphoma (19 cases), mantle cell lymphoma (4 cases), and B-cell lymphoblastic lymphoma (1 case). In BL, a homogeneous phenotype (CD10(+), Bcl-6(+), Bcl-2(-), MUM1/IRF4-, and Ki-67 approximately 100%) and a stable Epstein-Barr virus integration were found. A distinctive and unusual feature was the frequent plasma cellular differentiation, along with the positivity for CD30 and CD138 (recorded in 35 and 43 cases, respectively). According to our findings, most non-Hodgkin B-cell tumors in Uganda are endemic BLs followed by diffuse large B-cell lymphomas. The rest consist of rare but clinically important entities such as mantle cell lymphoma and B-cell lymphoblastic lymphoma. The availability of TMAs and immunohistochemistry has enabled us to precisely categorize tumors that have so far been diagnosed in Uganda as "high-grade/aggressive" lymphomas on the basis of cell morphology alone.     

Diffuse large B-cell lymphoma and its variants

According to the World Health Organization classification of neoplastic diseases of the hematopoietic and lymphoid tissues, diffuse large B-cell lymphoma comprises about 40% of adult cases of non-Hodgkin s lymphoma. It consists of the following morphological variants: 1) centroblastic (with or without multilobulated nuclei); 2) immunoblastic (>90% of immunoblasts); 3) T cell/histiocytes rich; and 4) anaplastic. Rare morphological variants plasmablastic type, mediastinal (thymic) diffuse large B-cell lymphoma, intravascular, and primary effusion B-cell lymphoma are considered distinct variants of diffuse large B-cell lymphoma due to their unique topographic presentation and clinical behavior, as well as immunophenotypic and genetic characteristics. T-cell/histiocyte-rich B-cell lymphoma is morphologically characterized by up to 25% of large neoplastic B cells and 75-90% of reactive, non-neoplastic T cells. Mediastinal (thymic) diffuse large B-cell lymphoma is considered a subtype of diffuse large B-cell lymphoma arising in the mediastinum, with distinctive morphological, immunohistochemical, genotypic, and clinical features. Mediastinal diffuse large B-cell lymphoma is an aggressive disease with poor outcome, which probably originates from thymic B cells at the terminal stage of differentiation. During the 1997-2001 period, 720 patients were diagnosed with non-Hodgkin s lymphoma in our institution. Out of 101 (14%) patients with diffuse large B-cell lymphoma, 17 had T-cell-rich B-cell lymphoma and their median survival was less than 20 months, with no difference regarding sex, bone marrow involvement, CD30 positivity, or histiocytic component of the tumor. Twenty out of 101 patients had mediastinal B-cell lymphoma and their median survival was 21 months, with sex or degree of necrosis of the involved lymph node having no impact on survival. We studied the frequency of bcl-2 gene rearrangement in fusion with immunoglobulin receptor gene of t(14;18) and found no such event among 20 of our patients with mediastinal diffuse large B-cell lymphoma. Despite extensive efforts and constant progress in our understanding of non-Hodgkin s lymphoma pathogenesis, the diffuse large B-cell lymphoma group remains heterogeneous entity awaiting further pathological and clinical stratification.     

Großzellige B-Zell-Lymphome Varianten und Entitäten

Large B-cell neoplasms represent one of the most frequent groups of non-Hodgkin-lymphomas (30-40%). They are characterized by an aggressive clinical course. These lymphomas may evolve either de novo or secondary during the course of a less aggressive lymphoma. In addition to primary nodal, a primary extranodal manifestation is rather common. The neoplastic cells, even within one given case, show a broad morphological spectrum. Several findings of the last two decades have revealed that the large B-cell lymphomas represent an inhomogeneous group. This fact has been taken into account by the new WHO classification of malignant lymphomas. There are two groups identified, that of the variants and that of the subtypes. The various variants (centroblastic, immunoblastic, anaplastic, T-cell/histiocyte-rich) correspond to lymphomas without reproducible discriminating criteria lacking characteristic clinical, immuno-phenotypical and genetic findings. In contrast, the primary mediastinal, the intravascular, the primary effusion and primary central nervous system lymphomas represent distinct disease entities. A number of recently described large cell lymphoma types, i.e. plasma-blastic, ALK-positive and primary gastric, are included in the classification, their designation as distinct entities is still under discussion.     

Primary malignant lymphomas of the central nervous system: a histological and immunohistological study of 12 cases

Paraffin sections of surgical and autopsy material from 12 cases of primary non-Hodgkin's lymphomas of the central nervous system were examined for histopathological diagnosis and for the demonstration of cytoplasmic immunoglobulins. According to the Kiel classification, there were five cases of lymphoplasmacytoid polymorphous lymphoma, five of immunoblastic lymphoma, one of lymphoblastic lymphoma of convoluted cell type. There was also one of the recently described multilobated lymphoma. An immunohistological study of light and heavy chains by peroxidase-antiperoxidase (PAP) technique and avidin-biotin complex (ABC)technique was performed. Intracellular immunoglobulins were demonstrated in seven cases: four cases were classified as immunoblastic lymphomas and three cases as lymphoplasmacytoid lymphomas. Negative immunoglobulin staining was observed in five cases: two lymphoplasmacytoid lymphomas, one immunoblastic, one lymphoblastic of convoluted cell type and one multilobated. A 'monoclonal' pattern of immunoglobulin staining was detected in six cases. One case, classified as immunoblastic lymphoma, showed 'bitypic' staining for kappa and lambda chains. It was concluded that primary CNS non-Hodgkin's lymphomas of the present series showed morphological and immunohistological features similar to those of malignant lymphomas arising in extraneural sites. In particular, the presence in our series of a multilobated lymphoma, as a primary CNS tumour, is emphasized.     

Primary pulmonary non-Hodgkin's lymphomas

We report a retrospective study of the pathological features in 69 primary pulmonary non-Hodgkin's lymphomas which have previously been clinically reviewed. The tumours consisted of 61 (88%) low-grade and eight (12%) high-grade malignant lymphomas. Fifty-four of the low-grade malignant lymphomas were MALT lymphomas. Lymphoepithelial lesions were observed in bronchial, bronchiolar and alveolar lining. All tumours were composed of nodules, forming a lymphangitic pattern at the periphery and a confluent central mass. Invasion of pleura and vessels was often seen but this without any consequence on survival. Granulomas were found in 20% of cases. Six of the eight high-grade tumours were centroblastic and another two were B-cell lymphomas of undetermined type. In four cases, associated areas of low-grade malignant lymphoma with lympho-epithelial lesions indicated a preexisting MALT lymphoma. Clinical data suggest that limited surgery or non-aggressive chemotherapy can provide long-term survival in patients with such slowly developing neoplasms. However, non-invasive diagnostic methods need to be developed.     

Leu-M1 antigen expression in acute leukaemias

Leu-M1 is a differentiation antigen present in human myelomonocytic cells. Seventy-seven acute leukaemias were retrospectively stained with anti-Leu-M1 using the immunoperoxidase technique on Bouin-fixed paraffin-embedded sections. The subjects were 44 acute lymphoblastic leukaemias (ALL) and 33 acute myeloid leukaemias (AML) previously characterized by cytochemical and immunologic (cell suspension) methods. Leu-M1 was positive in all the AML and in half of the ALL cases. These results suggest that Leu-M1 does not allow differentiation between AML and ALL. For the ALL cases Leu-M1 was positive in 15/28 B-cell types, 4/12 T-cell type and 3/4 'null'-cell type cases. Thus, this antibody is of no assistance in defining types B, T, or 'null' in ALL. Leu-M1 was also studied on paraffin sections of 34 high grade malignant lymphomas. The antibody was negative in all 13 B-cell lymphomas (lymphoblastic: 6; immunoblastic: 7) and in all 4 'null' cell lymphomas. It was positive in 4/9 peripheral T-cell type, the other T-cell lymphomas (lymphoblastic: 5; immunoblastic: 3) remaining negative. Thus, Leu-M1 may be positive in T-cell lymphomas but it is negative in B-cell lymphomas and is always negative in B or T lymphoblastic types. It seems that lymphoblasts are Leu-M1 negative in non-Hodgkin's lymphoma and may be Leu-M1 positive in leukaemias.     

Primary high-grade malignant lymphomas of bone

Summary Five cases of primary high-grade malignant lymphoma of bone are presented. The tumours occurred at a single site in all the cases and produced osteopathic lesions. Histologically, they were large cell tumours characterized by round to irregularly shaped nuclei with finely distributed heterochromatin and small to medium-sized nucleoli. The cytoplasm was moderate and slightly to moderately basophilic. In one case, giant cells similar to Hodgkin and Sternberg-Reed cells occured. The tumour cells bore B-cell markers but did not express immunoglobulin. Three of the bone tumours were polymorphic centroblastic lymphomas. The remaining two cases were also high-grade malignant B-cell lymphomas which may also be derived from germinal center cells but this could not be further substantiated.This study was supported by a grant from the Deutsche Forschungsgemeinschaft (Proj. 1284/1-1)     

Burkitt- und Burkitt-ähnliche Lymphome

Among aggressive mature B-cell lymphomas, a reproducible morphological and immunohistological distinction between Burkitt's lymphoma and diffuse large B-cell lymphoma (centroblastic variant) is impossible in a substantial number of cases. The German reference centres for hematopathology collected 220 retrospective cases of aggressive mature B-cell lymphoma whose classification according to the current World Health Organisation criteria was reviewed. Gene expression analysis (Affymetrix) was performed in all cases and chromosomal translocations were determined using fluorescence in situ hybridization. Chromosomal losses and gains were analysed by matrix comparative genomic hybridisation and clinical data were successfully collected for most patients. The application of a novel bioinformatics method led to the identification of a stable and reproducible gene expression signature specific for Burkitt's lymphoma. A total of 44 cases were identified by this molecular signature [designated molecular Burkitt's lymphoma (mBL)]. These molecular Burkitt's lymphomas showed the morphology and immunohistology of classical or atypical Burkitt's lymphoma cases in 29 instances. However, 15 of the molecular Burkitt's lymphoma cases had the morphology of diffuse large B-cell lymphoma or could not be further specified. All molecular Burkitt's lymphomas showed an expression of BCL-6 and CD10, but a MYC translocation was not demonstrable in more than 10% of cases. Of significance is that more than 20% of the molecular Burkitt's lymphomas expressed BCL-2, although weakly in most instances. Our data demonstrate that: (1) the morphological, immunophenotypical and genetic spectrum of Burkitt's lymphoma is broader than previously expected, and (2) our molecular Burkitt's lymphoma signature enables a more precise and extended definition this lymphoma.     

A case of primary osseous malignant immunoblastic B-cell lymphoma with intracytoplasmic mu lambda immunoglobulin inclusions

Primary malignant lymphoma of bone, so-called Parker-Jackson reticulosarcoma, is a rare form of extranodal lymphoma with a relatively good prognosis. It often corresponds to B-cell lymphoma of high-grade malignancy. We report a case of mu lambda immunoblastic lymphoma showing two distinctive features: an abundant reactive T-lymphocytic population and unusual intra-cytoplasmic inclusions. These inclusions were PAS positive and consisted of monotypic mu lambda immunoglobulin localized in peculiar aggregates of rough endoplasmic reticulum. Their morphological appearances resembled the well-documented inclusions described in some varieties of non-Hodgkin's lymphoma.     

Malignant lymphomas of the nasal cavity and paranasal sinuses

Summary The incidence of malignant lymphomas in the nasal cavity and paranasal sinuses was found tobe 0.17% of all malignant lymphomas and 0.44% of all extranodal malignant lymphomas registered in the Kiel Lymph Node Registry from 1972 to 1987. Fifty-nine cases of malignant lymphoma presenting in the nasal cavity and paranasal sinuses were investigated with morphological and immunological methods. The median age of the patients was 64.5 years, with a female predominance (m:f=0.87:1). In the 59 cases a marked preponderance of B-cell lymphomas was found (centroblasticn=15, immunoblasticn=8, Burkitt's lymphoman=6, Immunocytoman=3, centrocyticn=1, centroblastic/centrocyticn=1, plasmacyticn=11); only a small number (n=5) was of T-cell lineage (pleomorphic types). Nine further cases could not be assigned with certainty to either the T or B cell system. Angiocentricity with infiltration and destruction of vessel walls by tumour cells was demonstrated only in the T-cell lymphomas; the B-cell lymphomas, in contrast, of ten surrounded and compressed blood vessels with intact endothelium. No similarity to malignant lymphomas of mucosa associated lymphoid tissue, such as those in the gastrointestinal tract, was detected.     

WHAT IS BURKITT'S LYMPHOMA?

Burkitt's lymphoma (BL) has been defined on the basis of its characteristic cytomorphology. Although histologically identical, endemic BL and sporadic BL are distinct clinico-anatomical entities. Their morphological identity probably relates to similar chromosomal translocations in both tumours, resulting in c- myc de-regulation and consequent unrestrained proliferation without differentiation. Similar gene rearrangements are found in a proportion of AIDS-related lymphomas that are predominantly extranodal and have the cytomorphology of BL. The term “Burkitt-like lymphoma” (BLL) has been applied to a group of high-grade B-cell lymphomas that appear morphologically intermediate between BL and centroblastic/immunoblastic lymphomas, as detailed in an accompanying paper in this issue. These tumours do not usually show c- myc gene rearrangements. The association of Burkitt's name with such a disparate group of tumours is confusing and new terminology for sporadic BL, AIDS-related BL and BLL is desirable. It is important that clinico-anatomical features, as well as cytomorphology, should be taken into account in the diagnosis of endemic BL. The origin of a case from tropical Africa does not, in itself, imply that it is endemic BL, even more since the AIDS epidemic in that continent. © 1997 John Wiley & Sons, Ltd.     

Dipeptidyl aminopeptidase-IV as a histochemical marker of differential diagnosis of large cell anaplastic CD30+-lymphoma and Hodgkin's disease

Using histochemical methods, we studied distribution of dipeptidylaminopeptidase-IV (DPP-IV) in tumor cells of 16 patients with non-Hodgkin's malignant lymphomas (NHL) including B-cell NHL (10 cases), pleomorphic T-cell lymphoma (1 case), CD30+ anaplastic large cell lymphoma (ALCL) of T-cell (1 case) and ALCL of null-cell type (4 cases) and of 13 patients with Hodgkin's disease (HD). The results indicate that tumour cells of pleomorphic T-cell NHL and ALCL of T- and null-cell type showed DPP-IV activity. In contrast, no DPP-IV activity was seen in the tumor cells of B-cell NHL (lymphocytic, centroblastic/centrocytic, centroblastic, immunoblastic), in Berezovsky-Reed-Sternberg and Hodgkin's cells of different HD variants. These results demonstrate that difference in DPP-IV activity between tumor cells of ALCL and HD may be diagnostically important for separation of ALCL from HD and moreover may be used in verification of the borderline between HD-like ALCL and ALCL-like HD. It is possible that DPP-IV activity contributes to pathogenesis of ALCL and may determine clinical behaviour of this NHL being involved in autocrine and paracrine regulation of tumor cell growth of ALCL.     

Aggressive B-cell lymphomas with a primary bone marrow presentation

Aggressive B-cell lymphomas present as a heterogeneous spectrum of disease. A primary diagnosis in the bone marrow (BM) may be challenging in terms of diagnostic classification and clinical handling, owing to limited architectural information. Aggressive B-cell lymphomas can be subdivided into entities that typically present primarily in the BM, and cases with BM involvement in which the bulk of disease is present in other organs. One main topic at the 2018 BM workshop of the European Association of Haematopathology/Society of Hematopathology was therefore aggressive B-cell lymphomas with a primary BM presentation. The spectrum of cases submitted to this topic gave a good overview of commonly encountered problems, as well as unusual manifestations, and highlighted areas of imprecise disease definitions and diagnostic grey zones. The categories submitted to the workshop included cases of Burkitt lymphoma (BL) with unusual features, high-grade B-cell lymphomas (HG-BCLs) with and without so-called double/triple-hit, and diffuse large B-cell lymphomas (DLBCLs) with a primary BM presentation. Areas of difficulties included the morphological boundaries of HG-BCL not otherwise specified, cases with MYC and bcl-2 or bcl-6 translocations and terminal deoxynucleotidyl transferase (TdT) expression, which were categorised as B-cell lymphoblastic leukaemia/lymphoma if most cells showed TdT positivity, and the clinicopathological overlap between intravascular large B-cell lymphoma, CD5-positive DLBCL, and DLBCL with primary presentations in the BM, spleen, and liver. This review summarises our understanding of the main aggressive B-cell lymphoma categories with a common primary BM presentation and potential problem areas, and makes suggestions for the immunophenotypic and genetic work-up, illustrated by the interesting and challenging cases submitted to the workshop.