Evaluating breast lymphoplasmacytic infiltrates: a multiparameter immunohistochemical study, including assessment of IgG4

Lymphoplasmacytic infiltrates in the breast, a modified skin appendage, include lymphocytic lobulitis, other nonspecific benign proliferations, and mucosa-associated lymphoid tissue (MALT)-type lymphoma. Distinguishing these entities, all of which may be B-cell rich and may have associated sclerosis, can be difficult. In addition, the proportion that represents IgG4-related disease is unknown, and the similarity of MALT lymphomas to primary cutaneous marginal zone lymphoma is uncertain. To address these questions, the clinical, histologic, and immunohistochemical features of 50 benign and malignant breast lymphoplasmacytic infiltrates (10 lymphocytic lobulitis, 1 granulomatous, 19 not otherwise specified, 20 MALT lymphomas) were evaluated. Compared with the MALT lymphomas, benign cases had a less dense infiltrate (P < .001), fewer but more histologically apparent germinal centers (P < .001), and more marked fibrosis (P < .0001). Greater than 60% B cells were present in 23% (7/30) benign cases versus 75% (15/20) MALT lymphomas (P = .0003). Plasma cells were predominantly IgG+ in 83% (24/29) benign cases and predominantly IgM+ in 73% (14/19) MALT lymphomas (P < .0001). None of the benign cases had greater than 50 IgG4+ plasma cells/high-power field, and only 1 lymphocytic lobulitis case had an IgG4/IgG ratio exceeding 40% and no clinical evidence for extramammary IgG4-related disease. Although there may be some overlapping features, routine histopathology together with limited immunohistochemical stains can distinguish benign from neoplastic lymphoplasmacytic infiltrates in the breast. Despite frequent sclerosis, the breast is not a common site of unrecognized IgG4-related sclerosing disease. Although there are similarities, breast MALT lymphomas can be separated from cutaneous marginal zone lymphoma.

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

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

Utility of CD279/PD-1 immunohistochemistry in the evaluation of benign and neoplastic T-cell-rich bone marrow infiltrates

OBJECTIVES

CD279 expression is used to help identify angioimmunoblastic T-cell lymphoma (AITL) or other T-cell lymphomas of T-follicular helper (TFH) cell origin; however, its utility in assessing lymphoid infiltrates in the bone marrow (BM) is not well established.

METHODS

Immunohistochemistry for CD279 was performed on normal staging BM and in BM with benign lymphoid aggregates (LAs), AITLs, and other T-cell lymphomas.

RESULTS

Seven of 10 staging BMs demonstrated scattered, usually weakly CD279+ cells. Thirty-four of 38 BMs had scattered weakly/variably intense CD279+ cells within LAs, but only four contained 11% to 25% CD279+ cells. Three of four AITLs were strongly CD279+, but one contained only around 10% CD279+ cells. Eleven of the other 38 T-cell lymphomas were CD279+, including five possible AITLs; four peripheral T-cell lymphomas, not otherwise specified; and two T-cell large granular lymphocytic leukemias.

CONCLUSIONS

Although useful in assessing selected BM lymphoid infiltrates, CD279 expression may be limited in AITLs, is not specific for TFH lymphomas, and can be seen in benign lymphoid infiltrates, although without extensive strong positivity.

Whole-genome single nucleotide polymorphism array analysis is complementary to classical cytogenetic analysis in the evaluation of lymphoid proliferations

OBJECTIVES

To explore how much additional information single nucleotide polymorphism (SNP) arrays provide and whether they could partially replace classical cytogenetics.

METHODS

Twenty-six lymphoid proliferations with available cytogenetic studies were analyzed with the Affymetrix Genome-Wide Human SNP Array 6.0 (Affymetrix, Santa Clara, CA).

RESULTS

Eleven of 26 cases demonstrated complete concordance between cytogenetics and SNP analysis, and 10 of 26 cases demonstrated partial concordance. Five discordant cases had copy number abnormalities (CNAs) with cytogenetics not identified with SNP arrays. While SNP analysis showed CNAs not apparent by cytogenetics in eight cases and helped clarify the karyotype in six cases, cytogenetics demonstrated CNAs not seen by SNP analysis in 15 cases as well as balanced translocations in 12 cases.

CONCLUSIONS

The combination of cytogenetics and SNP analysis results in a higher overall yield in identifying numerical chromosomal abnormalities than either technique alone.

Splenic lymphoid subsets with less well-recognized phenotypes mimic aberrant antigen expression

OBJECTIVES

Flow cytometry can assist in the diagnosis of lymphoma by identifying aberrant antigen expression. Recognition of aberrancy requires knowledge of the phenotype of normal lymphoid cells.

METHODS

Lymphoid subsets were characterized in 20 spleens removed for traumatic rupture, using 8-color flow cytometry.

RESULTS

Normal variation in splenic lymphoid subsets was highlighted and several well-recognized subsets were identified: CD5+ B cells (20/20 specimens), CD7- T cells (20/20), and CD3 brightγδT cells (16/20). In addition, less well-recognized lymphoid subsets that resemble those described in lymphoma were identified in all specimens: CD5- T cells (4.5 ± 5.1% of T cells), CD2- natural killer (NK) cells (38 ± 7% of NK cells), and CD7dim+ NK cells. Similar populations were identified in 20 control peripheral blood specimens, where they represented a smaller proportion of total lymphoid cells.

CONCLUSIONS

Familiarity with the phenotype of normal lymphoid subsets can help prevent misinterpreting flow cytometric data. Furthermore, in the context of neoplastic cells, the phenotype may suggest expanded normal subsets rather than aberrant antigen expression.

Follicular lymphoma-like B cells of uncertain significance (in situ follicular lymphoma) may infrequently progress, but precedes follicular lymphoma, is associated with other overt lymphomas and mimics follicular lymphoma in flow cytometric studies

In situ follicular lymphoma, more recently known as follicular lymphoma-like B cells of uncertain/undetermined significance is well accepted. However, the morphological criteria have evolved since it was first described and data are limited and conflicting regarding its clinical implications and whether the extent of involvement predicts an association with overt lymphoma. It is also unknown how often it will be identified by flow cytometric studies and how often it precedes overt follicular lymphomas. A multiparameter study of 31 biopsies with follicular lymphoma-like B cells of uncertain significance and 4 'benign' lymph node biopsies that preceded an overt follicular lymphoma was, therefore, performed. Fifty-two percent of biopsies with follicular lymphoma-like B cells were associated with a prior or concurrent lymphoma but only 6% subsequently developed lymphoma (median follow up 26 months). Neither the number, proportion or density of BCL2(+) germinal centers were associated with overt follicular lymphoma/diffuse large B-cell lymphoma. Flow cytometric studies identified follicular lymphoma-like B cells in 8 of 15 evaluable cases. The proportion but not the absolute number of BCL2(+) germinal centers was associated with the likelihood of positive flow cytometric studies (P<0.01). All 4 'benign' biopsies that preceded an overt follicular lymphoma demonstrated follicular lymphoma-like B cells. Thus, although few patients with follicular lymphoma-like B cells of uncertain significance progress within the follow-up period, it at least precedes many follicular lymphomas. The extent of involvement does not predict the occurrence of prior or concurrent lymphomas. Flow cytometric studies demonstrating follicular lymphoma-like B cells must not be over-interpreted as they may only reflect follicular lymphoma-like B cells.

Non-mycosis fungoides cutaneous T-cell lymphomas: report of the 2011 Society for Hematopathology/European Association for Haematopathology workshop

Primary cutaneous T-cell lymphomas (CTCL) excluding mycosis fungoides (MF) were discussed in 2 sessions of the 2011 Society for Hematopathology/ European Association of Haematopathology Workshop, Los Angeles, CA. Session 2 focused on primary cutaneous CD30+ T-cell lymphoproliferative disorders and their differential diagnosis, including systemic CD30+ T-cell lymphoma secondarily infiltrating the skin. Interesting features like special morphologic variants and atypical phenotypes were presented. In addition, the possibility of rare ALK+ primary cutaneous lymphomas was discussed. Session 3 examined other more uncommon non-MF CTCLs, including subcutaneous panniculitis-like T-cell lymphoma, extranodal NK/T-cell lymphoma, hydroa vacciniforme-like T-cell lymphoma, and rare subtypes of primary cutaneous peripheral T-cell lymphoma, not otherwise specified. In addition, systemic T-cell lymphomas involving the skin secondarily, such as angioimmunoblastic T-cell lymphoma, were included in this session. In this report, novel findings, areas of special interest, and diagnostic challenges emerging from the cases submitted to the workshop will be highlighted. The necessity to integrate histologic, immunophenotypical, genetic, and in particular, clinical data to arrive at the correct diagnosis, and subsequently provide adequate treatment, is emphasized.

Mycosis fungoides: report of the 2011 Society for Hematopathology/European Association for Haematopathology workshop

Session 1 of the 2011 Workshop of the Society for Hematopathology and European Association for Haematopathology focused on mycosis fungoides (MF), the most common cutaneous lymphoma. The 62 cases in this case group demonstrated a wide spectrum of clinicopathologic features, including those seen in typical cases as well as those, by contrast, with atypical clinical history, morphology, immunophenotype, and/or genotype. Of the 62 cases, 27 (44%) were presented at the workshop and highlighted diagnostic challenges plus related issues. This report summarizes the approach recommended for making a confident diagnosis of MF and its clinically significant variants; emphasizes pitfalls in evaluating early MF, assessing nodal involvement, and diagnosing transformed MF; and discusses the relationship between MF and primary cutaneous CD30+ T-cell lymphoproliferative disorders. Last, Sézary syndrome is discussed, with concentration on those features distinct from MF.

Cutaneous B-cell lymphoproliferative disorders: report of the 2011 Society for Hematopathology/European Association for Haematopathology workshop

The diagnosis and classification of the cutaneous B-cell lymphomas can be quite a challenge, with a definitive diagnosis sometimes being elusive, even when an extensive workup has been performed. Distinction of benign from neoplastic disorders can be difficult, with some hyperplasias mimicking lymphomas and vice versa. There are only a limited number of skin-specific B-cell lymphomas, including primary cutaneous follicle center lymphoma and primary cutaneous diffuse large B-cell lymphoma, leg type. Cutaneous marginal zone lymphomas have distinctive features but are classified with the other mucosa-associated lymphoid tissue lymphomas. It is important, however, to also remember that many other B-cell lymphomas/ plasma cell neoplasms can primarily, or more often secondarily, involve the skin. Some may mimic one of the skin-specific lymphomas but have very different clinical implications. Iatrogenic and senescent immunodeficiency-associated lymphoproliferative disorders that are often Epstein-Barr virus (EBV) positive can also primarily involve the skin, including cases also known as EBV-positive mucocutaneous ulcer.

Intestinal γδ T-cell lymphomas are most frequently of type II enteropathy-associated T-cell type

Enteropathy-associated T-cell lymphoma includes type I cases and distinctive type II cases that, according to 2008 and 2010 World Health Organization descriptions, are T-cell receptor β+. Although T-cell receptor γδ enteropathy-associated T-cell lymphomas are reported, it is unknown if they have distinctive features and if they should be categorized as enteropathy-associated T-cell lymphoma or as a mucocutaneous γδ T-cell lymphoma. To address these questions, the clinicopathologic, immunophenotypic, molecular, and cytogenetic features of 5 γδ-enteropathy-associated T-cell lymphomas were investigated. Only 1 patient had celiac disease and had type I enteropathy-associated T-cell lymphoma, and the others fulfilled the histopathologic criteria for type II enteropathy-associated T-cell lymphoma. All lacked cutaneous involvement. A celiac disease-associated HLA type was found in the patient with CD and one of four others. All were T-cell receptor γ+, T-cell receptor δ+, βF1-, CD3+, CD7+, CD5-, CD4-, and TIA-1+ with variable staining for CD2 (3/5), CD8 (2/5), Granzyme B (1/5), and CD56 (4/5). Fluorescence in situ hybridization demonstrated 9q34 gains in 4 cases, with 9q33-34 gains by single nucleotide polymorphism in 3 of these. Single nucleotide polymorphism analysis also demonstrated gains in 5q34-q35.1/5q35.1 (4/5), 8q24 (3/5), and in 32 other regions in 3 of 5 cases. Vδ1 rearrangements were identified in 4 of 4 cases with documented clonality showing the same clone in normal-appearing distant mucosa (3/3 tested cases). Thus, γδ-enteropathy-associated T-cell lymphomas share many features with other enteropathy-associated T-cell lymphoma and are mostly of type II. Their usual nonactivated cytotoxic phenotype and Vδ1 usage are features unlike many other mucocutaneous γδ T-cell lymphomas but shared with hepatosplenic T-cell lymphoma. These findings support the conclusion that a γδ T-cell origin at extracutaneous sites does not define a specific entity.

Lymphoma classification and the tools of our trade: an introduction to the 2012 USCAP Long Course

The 2012 USCAP Long Course 'Malignant Lymphomas-Building on the Past, Moving to the Future' began with an introduction to lymphoma classification over the last half century and a discussion of our current diagnostic armamentarium, together with a look toward the future. The Rappaport classification, originally published in 1956, was a morphologic classification with few categories. The early 1970s saw a great and tumultuous revolution in the field with the publication of two functional lymphoma classifications that related the malignant lymphomas to the cells of the normal immune system-the Lukes/Collins classification from the United States and the Kiel classification from Professor Lennert and the European Lymphoma Club. With discord abounding, the NCI working formulation, published in 1982, satisfied some but was a step back to a morphologic-based classification. In 1994, the International Lymphoma Study Group published the REAL classification, which reflected state-of-the-art practice for that time, and was shortly followed by preparations for the modern World Health Organization (WHO) classification published in 2001 and revised in 2008. The WHO classification, created by hematopathologists working with the advice and consent of clinical hematologist/oncologists, recognizes numerous distinct entities, defined based on their histopathological, immunophenotypical, molecular/cytogenetic and clinical features. The classification requires use of a multiparameter approach to lymphoma diagnosis although we still rely heavily on histopathology. Immunophenotypical studies, whether using paraffin section immunohistochemistry and/or flow cytometry, are also critical in almost all circumstances. Molecular/cytogenetic techniques that are constantly changing have an increasingly important role, even if not always required. The full impact of next-generation sequencing is yet to be felt but we are beginning to catch a glimpse of what is in our future. Finally, one must not forget the great importance of clinical data in arriving at a diagnosis that best serves the patient, our ultimate goal.

Pulmonary extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue associated with granulomatous inflammation in a child with chromosome 22q11.2 deletion syndrome (DiGeorge syndrome)

Patients with immunodeficiency disorders have an increased incidence of lymphoproliferative disorders; however, only 4 such patients with DiGeorge/chromosome 22q11.2 deletion syndrome have been reported. We report a case of a pulmonary Epstein-Barr virus-negative extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue in a child with this syndrome.

Thyroid carcinoma-associated genetic mutations also occur in thyroid lymphomas

Molecular testing for mutations activating the mitogen-associated protein kinase signaling pathway is being used to help diagnose thyroid carcinomas. However, the prevalence of these mutations in thyroid lymphomas has not been reported. Therefore, we studied the prevalence of BRAF, NRAS, HRAS, and KRAS mutations in 33 thyroid lymphomas and correlated the mutational status with the clinical, pathological, cytogenetic, and immunophenotypic findings. Eleven cases were also tested for PAX8/PPARγ translocations. The lymphomas included 25 diffuse large B-cell lymphomas, 6 extranodal marginal-zone lymphomas of mucosa-associated lymphoid tissue type, and 2 follicular lymphomas. Seventeen diffuse large B-cell lymphomas were germinal center type, six non-germinal center type, and two unclassifiable (Hans algorithm). None of the cases had an associated thyroid carcinoma. Mutations of the BRAF gene were identified in six (24%) diffuse large B-cell lymphomas (D594G in three germinal center diffuse large B-cell lymphomas, K601N in two germinal center diffuse large B-cell lymphomas, and V600E in one non-germinal center diffuse large B-cell lymphoma) and of the NRAS gene in two (8%) non-germinal center diffuse large B-cell lymphomas (Q61K and Q61H). BRAF and NRAS mutations were not found in any extranodal marginal-zone lymphomas of mucosa-associated lymphoid tissue type or follicular lymphomas. HRAS and KRAS mutations were not identified in any of the cases, nor were PAX8/PPARγ translocations found. Thus, interpretation of finding a BRAF or NRAS mutation in the thyroid, particularly in preoperative thyroid aspirates, must take into account the differential diagnosis of a lymphoma. In addition to the diagnostic importance, our data also demonstrate that alteration in the mitogen-associated protein kinase pathway may have a role in the pathogenesis of some large B-cell lymphomas of the thyroid with potential therapeutic implications.

Composite mantle cell lymphoma and chronic lymphocytic leukemia/small lymphocytic lymphoma: a clinicopathologic and molecular study

Mantle cell lymphoma (MCL) and chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) share many features and both arise from CD5+ B-cells; their distinction is critical as MCL is a more aggressive neoplasm. Rarely, cases of composite MCL and CLL/SLL have been reported. Little is known about the nature of these cases and, in particular, the clonal relationship of the 2 lymphomas. Eleven composite MCL and CLL/SLL cases were identified. The clinical, morphologic and immunophenotypic features of the MCL and CLL/SLL were characterized. IGH (immunoglobulin heavy chain) gene analysis was performed on microdissected MCL and CLL/SLL components to assess their clonal relationship. Ten patients had lymphadenopathy, and 7 patients had bone marrow involvement. The MCL component had the following growth patterns: in situ (n = 1), mantle zone (n = 3), nodular and diffuse (n = 3), diffuse (n = 3), and interstitial in the bone marrow (the only patient without lymphadenopathy) (n = 1); 6 MCLs had blastoid or pleomorphic and 5 small lymphocytic features. The CLL/SLL component was nodular (n = 9) or diffuse (n = 2). All MCL were CD5(+) and cyclin D1(+) with t(11;14) translocation. All CLL/SLL were CD5(+), CD23(+) and negative for cyclin D1 or t(11;14). IGH gene analysis showed that the MCL and CLL/SLL components displayed different sized fragments, indicating that the MCL and CLL/SLL are likely derived from different neoplastic B-cell clones. The lack of a clonal relationship between the MCL and CLL/SLL components suggests that MCL and CLL/SLL components represent distinct disease processes and do not share a common progenitor B-cell.

Chronic lymphocytic leukemia/small lymphocytic lymphoma with cyclin D1 positive proliferation centers do not have CCND1 translocations or gains and lack SOX11 expression

Cyclin D1 expression, usually absent in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), has been described in the proliferation centers (PC) of some CLL/SLL. The prevalence of this finding is uncertain, as is the explanation for its occurrence and whether these cases have any other unique features. Cyclin D1 immunohistochemical staining was therefore investigated in 57 extramedullary CLL/SLL biopsies. In 6 cases, cyclin D1 immunofluorescence followed by CCND1 fluorescence in situ hybridization (FISH) and PC targeted analysis was performed using a Bioview Duet system. Excluding the prospectively selected cases that had the targeted FISH studies, cyclin D1+ PC were identified in 20% of cases. The cyclin D1+ CLL did not appear pathologically or phenotypically distinctive, though 46% had an interfollicular growth pattern. The cyclin D1+ PCs were SOX11- and lacked CCND1 translocations and gains in 5 of 5 informative cases. The recognition of cyclin D1 expression in PC of a significant minority of CLL/SLL can be a diagnostic aid and should not lead to the diagnosis of focal mantle cell lymphoma.

Mantle cell lymphoma as a component of composite lymphoma: clinicopathologic parameters and biologic implications

Composite lymphoma is a rare circumstance in which 2 or more distinct types of lymphoma occur in a single anatomical location. Although composite lymphoma has been increasingly identified with the advent of molecular genetic techniques, this topic has only rarely been a specific focus of the medical scientific literature. In this review, we focus on mantle cell lymphoma occurring as a major pathologic component of composite lymphoma and emphasize the clinicopathologic features of these tumors and associated biologic implications. To date, 26 cases of composite lymphoma including a component of mantle cell lymphoma have been previously published. Issues of clonal relatedness between the individual lymphoma components and emerging biologic implications as well as potential diagnostic pitfalls are evaluated.

In situ mantle cell lymphoma: clinical implications of an incidental finding with indolent clinical behavior

BACKGROUND

Cyclin D1-positive B cells are occasionally found in the mantle zones of reactive lymphoid follicles, a condition that has been called "in situ mantle cell lymphoma". The clinical significance of this lesion remains uncertain.

DESIGN AND METHODS

The clinical and pathological characteristics, including SOX11 expression, of 23 cases initially diagnosed as in situ mantle cell lymphoma were studied.

RESULTS

Seventeen of the 23 cases fulfilled the criteria for in situ mantle cell lymphoma. In most cases, the lesions were incidental findings in reactive lymph nodes. The t(11;14) was detected in all eight cases examined. SOX11 was positive in seven of 16 cases (44%). Five cases were associated with other small B-cell lymphomas. In two cases, both SOX11-positive, the in situ mantle cell lymphoma lesions were discovered after the diagnosis of overt lymphoma; one 4 years earlier, and one 3 years later. Twelve of the remaining 15 patients had a follow-up of at least 1 year (median 2 years; range, 1-19.5), of whom 11 showed no evidence of progression, including seven who were not treated. Only one of 12 patients with an in situ mantle cell lymphoma lesion and no diagnosis of mantle cell lymphoma at the time developed an overt lymphoma, 4 years later; this case was also SOX11-positive. The six remaining cases were diagnosed as mantle cell lymphoma with a mantle zone pattern. Five were SOX11-positive and four of them were associated with lymphoma without a mantle zone pattern.

CONCLUSIONS

In situ mantle cell lymphoma lesions are usually an incidental finding with a very indolent behavior. These cases must be distinguished from mantle cell lymphoma with a mantle zone pattern and overt mantle cell lymphoma because they may not require therapeutic intervention.

Lymphoplasmacytic lymphoma and other non-marginal zone lymphomas with plasmacytic differentiation

Small B-cell lymphomas with plasmacytic differentiation frequently present diagnostic challenges. Session 3 of the 2009 Society for Hematopathology/European Association for Haematopathology Workshop focused on lymphoplasmacytic lymphoma (LPL). The submitted cases illustrated classic examples of bone marrow-based and nodal LPL and cases with atypical features, including unusual phenotypes or involvement of extranodal sites. Several cases showed varying degrees of overlap with marginal zone lymphoma, and, as acknowledged in the 2008 World Health Organization classification, a definitive distinction between these 2 possibilities cannot always be established. Session 6 of the workshop focused on other non-marginal zone lymphomas that may display plasmacytic differentiation. This session highlights the wide variety of neoplasms that enter into the differential diagnosis of small B-cell lymphomas with plasmacytic differentiation and demonstrates the use of clinical features and ancillary studies in establishing an appropriate diagnosis by 2008 World Health Organization criteria.

Marginal zone lymphomas with plasmacytic differentiation and related disorders

Marginal zone lymphomas of all types (nodal, splenic, and extranodal mucosa-associated lymphoid tissue [MALT]) may show plasmacytic differentiation. Distinguishing marginal zone lymphomas from other small B-cell lymphomas with plasmacytic differentiation, especially lymphoplasmacytic lymphoma, or from plasma cell neoplasms may be challenging. Marginal zone lymphomas with plasmacytic differentiation were discussed in 2 sessions of the 2009 Society for Hematopathology/European Association for Haematopathology Workshop. Session 4 focused on nodal marginal zone lymphomas, including cases exhibiting classic features and cases displaying atypical phenotypes. The difficulties of classification of cases with increased numbers of large cells were also discussed. Session 5 examined nonnodal marginal zone lymphomas and related entities, including splenic marginal zone lymphoma, MALT lymphoma, γ heavy chain disease, and cryoglobulin-associated lymphoproliferative disorders. These cases illustrate the importance of clinical data and, in some cases, phenotypic and cytogenetic findings in appropriately applying the 2008 World Health Organization criteria.

Reassessment of small lymphocytic lymphoma in the era of monoclonal B-cell lymphocytosis

BACKGROUND

In the 2008 World Health Organization classification, small lymphocytic lymphoma is defined as a neoplasm with the tissue morphology and immunophenotype of chronic lymphocytic leukemia, but with absence of leukemia. Minimal criteria of tissue involvement to separate small lymphocytic lymphoma from monoclonal B-cell lymphocytosis have not been defined.

DESIGN AND METHODS

We reviewed the clinicopathological features of 36 patients with extramedullary tissue biopsies containing chronic lymphocytic leukemia-type cells and less than 5×10(9)/L peripheral blood monoclonal B cells. Pathological features (extent and patterns of involvement, architectural preservation, presence of proliferation centers) as well as cytogenetic and radiological findings were examined in relation to clinical outcome.

RESULTS

The biopsies were performed to evaluate lymphadenopathy in 20 patients and for other reasons (most frequently staging of a non-hematologic neoplasm) in 16 patients. At latest follow-up (median 23 months), 21 untreated patients had no or stable lymphadenopathy, 3 had regressed lymphadenopathy, and 12 had developed progressive lymphadenopathy and/or received therapy for chronic lymphocytic leukemia/small lymphocytic lymphoma. Features associated with progression/treatment included lymph nodes 1.5 cm or greater on imaging studies (P=0.01) and presence of proliferation centers in the biopsied tissue (P=0.004). Neither the size nor extent of involvement of the excised lymph node correlated with progression/treatment.

CONCLUSIONS

Our findings suggest that biopsies containing chronic lymphocytic leukemia-type cells, but lacking proliferation centers and with non-enlarged or only slightly enlarged lymph nodes on imaging, represent a very indolent disease that may best be considered a tissue equivalent of monoclonal B-cell lymphocytosis rather than overt small lymphocytic lymphoma. We propose that such cases be designated as tissue involvement by chronic lymphocytic leukemia/small lymphocytic lymphoma-like cells of uncertain significance.

Natural killer cell subsets and natural killer-like T-cell populations in benign and neoplastic B-cell proliferations vary based on clinicopathologic features

Microenvironmental factors play a critical role in B-cell lymphomas. Most studies emphasize the role of lymphoma-infiltrating T-cells and macrophages, with few studies on natural killer cells. Natural killer cells include a less mature (CD56(bright)/CD16-) subset that is more common in lymph nodes and a more mature (CD56(dim)/CD16+) subset that is more numerous in peripheral blood. Therefore, the proportions of natural killer cells, natural killer subsets, and natural killer-like T-cells (CD3+, CD56+, and/or CD16/57+) were determined by flow cytometry in 150 cases of tissue-based B-cell non-Hodgkin lymphoma and 89 nonneoplastic tissue biopsies. Results were correlated with the clinicopathologic findings. A higher percentage of natural killer cells was found in nonneoplastic spleen versus other nonneoplastic tissue (P < .001), in splenic-based B-cell non-Hodgkin lymphoma versus other B-cell non-Hodgkin lymphoma (P < .01), and in stage II to IV diffuse large B-cell lymphoma versus stage I diffuse large B-cell lymphoma (n = 19, P = .02). The more mature natural killer subset was increased in benign spleen (P < .001) and nonsplenic B-cell non-Hodgkin lymphoma (P < .01) versus nonsplenic, nonneoplastic tissue; in diffuse large B-cell lymphoma versus other B-cell non-Hodgkin lymphoma (P < .001); and in follicular lymphoma with an intermediate follicular lymphoma international prognostic index score (n = 17, P = .04). A higher proportion of natural killer-like T-cells was seen in diffuse large B-cell lymphoma versus other B-cell non-Hodgkin lymphoma (P = .001), whereas chronic lymphocytic leukemia/small lymphocytic lymphoma contained fewer natural killer-like T-cells (P < .001). The proportions of natural killer cells, natural killer subsets, and natural killer-like T-cells vary with tissue site, type of B-cell non-Hodgkin lymphoma, and clinical stage in diffuse large B-cell lymphoma and follicular lymphoma. A higher proportion of CD56(dim)/CD16/57+ natural killer cells is found in spleen, in more aggressive B-cell non-Hodgkin lymphoma, and in follicular lymphoma with an intermediate follicular lymphoma international prognostic index score. This may be of importance with increasing therapeutic use of immunomodulatory agents.

Molecular characteristics of mantle cell lymphoma presenting with clonal plasma cell component

The normal counterparts of mantle cell lymphoma (MCL) are naive, quiescent B cells that have not been processed through the germinal center (GC). For this reason, although lymphomas arising from GC or post-GC B cells often exhibit plasmacytic differentiation, MCL rarely presents with plasmacytic features. Seven cases of MCL with a monotypic plasma cell (PC) population were collected from 6 centers and were studied by immunohistochemistry, fluorescence immunophenotyping and interphase cytogenetics as a tool for the investigation of neoplasms analysis, capillary gel electrophoresis, and restriction fragment length polymorphism of immunoglobulin heavy chain analysis of microdissections of each of the MCL and PC populations to assess their clonal relationship. The clinical presentation was rather unusual compared with typical MCL, with 2 cases arising from the extranodal soft tissues of the head. All MCL cases were morphologically and immunohistochemically typical, bearing the t(11;14)(q13;q32). In all cases, the PC population was clonal. In 5 of the 7 cases, the MCL and PC clones showed identical restriction fragments, indicating a common clonal origin of the neoplastic population. The 2 cases with clonal diversity denoted the coexistence of 2 different tumors in a composite lymphoma/PC neoplasm. Our findings suggest that MCL can present with a PC component that is often clonally related to the lymphoma, representing a rare but unique biological variant of this tumor.

Flow cytometric immunophenotyping of cerebrospinal fluid specimens

Flow cytometric immunophenotyping (FCI) is recommended in the evaluation of cerebrospinal fluid (CSF) specimens for hematologic neoplasms. This study reviewed FCI of CSF specimens collected for primary diagnosis (n = 77) and follow-up for known malignancy (n = 153). FCI was positive in 11 (4.8%) of 230 specimens: acute myeloid leukemia, 6; precursor B-acute lymphoblastic leukemia, 2; B-cell lymphoma, 2; and T-cell lymphoma, 1. Positive results were obtained in low-cellularity specimens, including 2 with fewer than 100 events in the population of interest. FCI was indeterminate in 19 (8.3%) of 230 specimens, including 3 with only sparse events, 8 with possible artifact (apparent lack of staining, nonspecific or background staining, and aspirated air), and 8 with phenotypic findings considered insufficient for diagnosis. Indeterminate specimens were often limited by low cellularity and lacked normal cell populations to evaluate for appropriate staining. FCI may be of value in low-cellularity CSF specimens, although the results should be interpreted with caution.

Simultaneous detection of imprinted gene expression (p57(KIP2)) and molecular cytogenetics (FICTION) in the evaluation of molar pregnancies

OBJECTIVE

To simultaneously evaluate the p57(KIP2) antibody expression and genotype of individual cells from paraffin sections of molar pregnancies.

STUDY DESIGN

Paraffin sections from 10 typical and unusual molar pregnancies were evaluated with the FICTION technique (Fluorescence Immunophenotyping and Interphase Cytogenetics as a Tool for the Investigation of Neoplasms), using immunofluorescence staining for the p57(KIP2) antibody and enumeration fluorescence in situ hybridization (FISH) probes. The unusual cases included androgenetic/ biparental chimeric complete hydatidiform moles (CHM) and mosaic partial hydatidiform moles (PHM). The unusual molar conceptions provided insight into interpreting atypical p57(KIP2) staining patterns and identifying androgenetic cells.

RESULTS

The androgenetic/biparental chimeric CHMs demonstrated a negative p57(KIP2) Staining pattern for the androgenetic cells and positive staining for the biparental cells. Concordantly, the FISH results showed delineation between the androgenetic cells and the biparental cells, indicating 2 distinct genotypes. Also, in the 2 cases of mosaic PHM, the partial loss of p57(KIP2) antibody staining was due to mosaic loss of chromosome 11, assumed to be the maternal copy. This provides a biological explanation as to how false interpretation could occur when evaluating p57(KIP2) immunostaining results.

CONCLUSION

The FICTION technique is a valuable ancillary tool for simultaneously evaluating the genotype and p57(KIP2) expression in unusual molar pregnancies.

Defining the borders of splenic marginal zone lymphoma: a multiparameter study

Classic splenic marginal zone lymphomas are CD5-, CD10-, CD23-, CD43-, and usually IgD+ with biphasic white pulp nodules. However, the 2008 World Health Organization classification accepts splenic marginal zone lymphomas with monophasic marginal zone-like white pulp nodules and recognizes a group of unclassifiable splenic small B-cell lymphomas. To explore the relationship of classic splenic marginal zone lymphomas to these other less well-defined splenic lymphomas, a multiparameter study of 47 splenic marginal zone lymphomas and unclassifiable splenic small B-cell lymphomas was performed. Seventeen of 31 splenic marginal zone lymphomas were biphasic, and 14 were monophasic (90%-100% marginal zone-like white pulp nodules). Sixteen cases were unclassifiable splenic small B-cell lymphomas, most lacking a marginal zone-type component. There were many clinical similarities between the 3 groups, including similar survivals. Monophasic and unclassifiable cases were less likely to have a typical splenic marginal zone lymphoma phenotype (28.6%, 23.1%) compared with biphasic cases (86.7%), usually because of IgD negativity (P < .003). Thirty-four of 42 (81%) cases had cytogenetic abnormalities by fluorescence in situ hybridization; and 17 of 20 (85%), by classical cytogenetics. The most frequent fluorescence in situ hybridization abnormalities among the splenic marginal zone lymphomas were del(7)(q31) (26%), +12 (25%), and +3q27 (27%); and among the unclassifiable cases, +12 (50%) and +3q27 (36%). Five of 6 unclassifiable cases with exclusively small non-marginal zone-like lymphocytes involving both white and red pulp had +12 compared with 9 of 34 other cases (P < .02). CDK6 (2 cases) and BCL3 (1 case) rearrangements were only seen in the unclassifiable group. These results support including both biphasic and monophasic cases as splenic marginal zone lymphomas, but suggest that the lack of a non-marginal zone-like population in the monophasic group is associated with some biologic differences. They also demonstrate a relatively large proportion of unclassifiable cases, including a group with frequent +12.

Genomic and gene expression profiling defines indolent forms of mantle cell lymphoma

Mantle cell lymphoma (MCL) is typically a very aggressive disease with poor outcomes, but some cases display an indolent behavior that might not necessitate treatment at diagnosis. To define molecular criteria that might permit recognition of such cases, we compared the clinicopathologic features, gene expression, and genomic profile of patients who had indolent or conventional disease (iMCL or cMCL). Patients with iMCL displayed nonnodal leukemic disease with predominantly hypermutated IGVH and noncomplex karyotypes. iMCL and cMCL shared a common gene expression profile that differed from other leukemic lymphoid neoplasms. However, we identified a signature of 13 genes that was highly expressed in cMCL but underexpressed in iMCL. SOX11 was notable in this signature and we confirmed a restriction of SOX11 protein expression to cMCL. To validate the potential use of SOX11 as a biomarker for cMCL, we evaluated SOX11 protein expression in an independent series of 112 cases of MCL. Fifteen patients with SOX11-negative tumors exhibited more frequent nonnodal presentation and better survival compared with 97 patients with SOX11-positive MCL (5-year overall survival of 78% versus 36%, respectively; P = 0.001). In conclusion, we defined nonnodal presentation, predominantly hypermutated IGVH, lack of genomic complexity, and absence of SOX11 expression as qualities of a specific subtype of iMCL with excellent outcomes that might be managed more conservatively than cMCL.

Follicular lymphomas with plasmacytic differentiation include two subtypes

Follicular lymphomas with plasmacytic differentiation were described more than two decades ago. However, the possibility that some of these reported cases are marginal zone lymphomas or composite lymphomas must be considered. In addition, it is also uncertain whether follicular lymphomas with plasmacytic differentiation have any unique cytogenetic or other features. Therefore, fluorescence immunophenotypic and interphase cytogenetic analysis of 14 well-characterized follicular lymphomas with plasmacytic differentiation was performed using a CD138 antibody to identify the plasma cells and with BCL2, BCL6, IGH@ and MALT1 break-apart probes and a chromosome 12 centromeric probe. CD10 was expressed in 12/14 cases, BCL6 in 12/12 cases and BCL2 in 12/14 cases. At least one cytogenetic abnormality was identified in 12/14 cases. The same abnormality was present in both the plasmacytic (CD138+) and non-plasmacytic (CD138-) component in all 10 evaluable cases. BCL2 rearrangements were present in seven cases (5 IGH@ rearranged, 1 IGH@-not rearranged, 1 IGH@-not evaluable), BCL6 rearrangement in two (1 also with BCL2/IGH@ rearrangement), +12 in 1, +MALT1 without +18 in 1, IGH@ rearrangement without other abnormalities in 1 and IGH@ rearranged or partially deleted in 1 case. No cases showed +BCL6 (3q27) or a MALT1 rearrangement. All six cases with an isolated BCL2 rearrangement had predominantly interfollicular plasmacytic cells whereas, 6/7 cases without the translocation had concentrations of intrafollicular or perifollicular plasmacytic cells (P<0.005), as did the case with BCL2 and BCL6 translocations. These results support the existence of bona fide follicular lymphomas with plasmacytic differentiation and support the clonal relationship of the neoplastic lymphoid and plasma cells in at least most of these cases. The differential distribution of the plasma cells, specifically in relation to the presence or absence of an isolated BCL2 rearrangement suggests that the latter cases may be distinctive, sharing some features with marginal zone lymphomas.

Human Merkel cell polyomavirus infection I. MCV T antigen expression in Merkel cell carcinoma, lymphoid tissues and lymphoid tumors

Merkel cell polyomavirus (MCV) is a recently discovered human virus closely related to African green monkey lymphotropic polyomavirus. MCV DNA is integrated in approximately 80% of Merkel cell carcinomas (MCC), a neuroendocrine skin cancer linked to lymphoid malignancies such as chronic lymphocytic leukemia (CLL). To assess MCV infection and its association with human diseases, we developed a monoclonal antibody that specifically recognizes endogenous and transfected MCV large T (LT) antigen. We show expression of MCV LT protein localized to nuclei of tumor cells from MCC having PCR quantified MCV genome at an average of 5.2 (range 0.8-14.3) T antigen DNA copies per cell. Expression of this putative viral oncoprotein in tumor cells provides the mechanistic underpinning supporting the notion that MCV causes a subset of MCC. In contrast, although 2.2% of 325 hematolymphoid malignancies surveyed also showed evidence for MCV infection by DNA PCR, none were positive at high viral copy numbers, and none of 173 lymphoid malignancies examined on tissue microarrays expressed MCV LT protein in tumor cells. As with some of the other human polyomaviruses, lymphocytes may serve as a tissue reservoir for MCV infection, but hematolymphoid malignancies associated with MCC are unlikely to be caused by MCV.

Comparison of Bcl-2, CD38 and ZAP-70 Expression in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) was previously considered a uniform disease characterized by autonomous over-expression of bcl-2. Recently the pathogenic role of bcl-2 has been questioned and attention has turned to prognostic subtypes of CLL differing in CD38 and ZAP-70 expression. However, the relationship between bcl-2 and CD38 or ZAP-70 expression remains uncertain and was investigated using flow cytometric immunophenotyping of 50 CLL specimens. CLL cells were consistently bcl-2 positive but varied in expression level: mean fluorescence intensity (MFI) 45-152. Although there was no significant difference in bcl-2 expression between CD38 or ZAP-70 positive and negative specimens, an inverse correlation was identified between percentage of CD38 positive B-cells and bcl-2 MFI when all (p<0.03, r(2)=0.10) and peripheral blood (p<0.004, r(2)=0.27) samples were analyzed. While bcl-2 levels do not appear to be a major discriminator between indolent and more aggressive subtypes of CLL, CD38 and bcl-2 expression appear to be interrelated.

Use of similar immunoglobulin VH gene segments by MALT lymphomas of the ocular adnexa

Extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue type (MALT lymphomas) develop from acquired reactive infiltrates directed against external or autoantigens. Although some European cases of ocular adnexal MALT lymphoma have been associated with Chlamydia psittaci infections, C. psittaci has not been detected in large studies of US-based cases. To evaluate whether the growth of US-based ocular adnexal MALT lymphomas may be promoted by a similar antigen, we identified and analyzed the expressed immunoglobulin VH genes in 10 cases. Interestingly, the VH genes in two cases used the same VH1 family V1-2 gene segment, and three cases used the same VH4 family V4-34 gene segment. The other five cases all used different gene segments V4-31, V5-51, V3-23, V3-30, and V3-7. All of the VH genes were mutated from germ line, with percent homologies ranging between 96.9 and 89.0%. The distribution of replacement and silent mutations within the VH genes was nonrandom consistent with the maintenance of immunoglobulin function and also strongly suggestive of antigen selection in the six VH genes with highest mutation loads. The CDR3 sequences in two of three VH-34 cases were the same size (15 amino acids) and had similar sizes in the two VH1-2 cases (18 and 16 amino acids). In conclusion, US-based MALT lymphomas of the ocular adnexa preferentially express a limited set of VH gene segments not frequently used by other MALT lymphomas and consistent with some recognizing similar antigens. Analysis of somatic mutations present within the VH genes is also consistent with antigen binding stimulating the growth of these lymphomas.

Best practices in contemporary diagnostic immunohistochemistry: panel approach to hematolymphoid proliferations

CONTEXT

The complexities of diagnostic hematopathology in the modern era are well known, and even in this molecular era, immunophenotypic studies, together with routine histopathology, remain a critical component in the evaluation of many lymphoid proliferations. With numerous antibodies that can be used on routinely fixed, paraffin-embedded tissue sections, immunohistochemistry has become increasingly valuable. It then becomes a challenge knowing the best approach to the selection of antibodies to use and how to interpret them.

OBJECTIVE

To present a pragmatic immunohistochemical approach to the evaluation of lymphoid proliferations that stresses the utility of 2 limited panels to deal with the most commonly encountered lymphomas.

DATA SOURCES

English-language literature published between 1990 and 2008.

CONCLUSIONS

A relatively limited panel of immunohistochemical stains may be used to diagnose and subclassify many of the more common lymphomas, although some cases will require additional stains and others fewer, depending on the case complexity. Immunohistochemical stains must always be interpreted in the context of the histopathologic and other ancillary studies.

Follicular lymphoma of the spleen: multiparameter analysis of 16 cases

Follicular lymphoma (FL) involving the spleen must be distinguished from reactive hyperplasia and from other lymphomas. A prior study reported that splenic FLs frequently lack BCL2 expression, further complicating diagnosis. We examined 16 cases of splenic FL, including 12 cases initially diagnosed at splenectomy. Two morphologic patterns were identified: one with architectural abnormalities (AA) and one with an extensive architectural preservation (AP) pattern. Newly diagnosed AP cases were associated with older age (P = .051) and grade 1 histologic features (P = .023). All cases displayed a CD10+/BCL2+ phenotype. Cytogenetics and FISH identified IGH/BCL2 or BCL6 translocations in all tested cases. Splenic FLs display phenotypic and cytogenetic findings similar to nodal FLs. However, splenic FLs frequently display an exclusively intrafollicular growth pattern resembling so-called in situ FL. Recognition of subtle FL with preserved architecture is important because patients may have overt FL at other sites or the FL may progress to overt nodal disease.

Phase II trial of short-course CHOP-R followed by 90Y-ibritumomab tiuxetan and extended rituximab in previously untreated follicular lymphoma

PURPOSE

Radioimmunotherapy has been approved for relapsed follicular lymphoma (FL), including rituximab-refractory FL. This study was designed to determine the CR rate with short-course chemoimmunotherapy with cyclophosphamide, doxorubicin, vincristine, prednisone, and rituximab (CHOP-R) followed by 90-Y ibritumomab tiuxetan (RIT) with extended rituximab as first-line treatment.

EXPERIMENTAL DESIGN

Between March 2004 and February 2007, 60 patients with stage II to IV symptomatic or bulky FL from a single institution supported by a large community network entered this phase II trial. Patients received CHOP-R for three treatment cycles before RIT followed by four additional weekly treatments with rituximab. Response was determined using fusion [(18) F] fluorodeoxyglucose-positron emission tomography (PET)-computed tomography (CT) imaging.

RESULTS

Of the 60 patients entering this trial, 55 patients completed all protocol therapy. The median follow up was 19.7 months (range, 0.26-35.9 months). For intent-to-treat analysis, the complete response (CR) rate after CHOP-R, as assessed by CT and PET imaging, was 40% and 46%, respectively. After RIT, the CR rate improved, as assessed by CT and PET imaging, to 82% and 89%, respectively. Ten patients have progressed, including eight from best response of CR. Seven of 18 patients who were PET positive after CHOP-R progressed compared with 3 of 37 patients who were PET negative (P=0.010).

CONCLUSIONS

In patients with previously untreated, symptomatic or bulky FL, short-course chemoimmunotherapy and consolidation RIT and extended rituximab resulted in a high CR rate. Failure to achieve an early PET CR after CHOP-R indicated high risk of relapse.

Primary cutaneous marginal zone B-cell lymphoma: a molecular and clinicopathological study of cases from Asia, Germany, and the United States

Primary cutaneous marginal zone B-cell lymphoma is considered the cutaneous counterpart of extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue. Although its molecular pathogenesis is currently unknown, an etiological link with Borrelia burgdorferi infection has been identified in European, but not in American or Asian cases. To better understand the pathogenesis and the geographical differences of cutaneous marginal zone B-cell lymphoma, 60 cases from the East Asia, Germany, and the United States at their initial presentation were subjected to the following analyses; (1) clinicopathological comparison between the geographical regions, (2) detection of B. burgdorferi DNA, (3) detection of the API2-MALT1 fusion transcript, a gene alteration specific to mucosa-associated lymphoid tissue lymphoma, and (4) inactivation of tumor suppressor genes (death-associated protein kinase (DAPK), p16(INK4a), p14(ARF), MGMT, TIMP3, CDH1, and RARB) by hypermethylation of the CpG islands. Cases from the three geographical regions showed similar clinicopathological features. However, moderate/marked tissue eosinophilia was found in 9/25 Asian cases, but only 1/23 German cases (P=0.011) and 0/12 American cases (P=0.015). All 60 cases were negative for either Borrelia DNA or API2-MALT1 fusion. Tumors from the three regions were highly methylated for DAPK (38-50% of the cases, mean 43%) and p16(INK4a) (42-70%, mean 49%), and the positivities were significantly higher than those of nonneoplastic skin (8%, P=0.0010 and 14%, P=0.0032, respectively). Methylation of these genes had no significant association with progressive features of the tumor. Primary cutaneous marginal zone B-cell lymphomas from the three geographical regions have common clinicopathological features, however, moderate/marked tissue eosinophilia is a feature found almost exclusively in Asian cases. Borrelia infection and API2-MALT1 fusion are not significant in this tumor. Methylation of DAPK and p16(INK4a) genes is a frequent event in this lymphoma at its initial presentation, but may not be associated with tumor progression.

Cytogenetic abnormalities detected by fluorescence in situ hybridization on paraffin-embedded chronic lymphocytic leukemia/small lymphocytic lymphoma lymphoid tissue biopsy specimens

Cytogenetic fluorescence in situ hybridization (FISH) panels are a major prognostic tool in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), but few data exist on using paraffin-embedded extramedullary tissue biopsy specimens for these purposes. Isolated whole nuclei were extracted from 20 paraffin-embedded tissue biopsy specimens with CLL/SLL and analyzed using a standard CLL FISH panel. FISH studies were successful in 18 (90%) of 20 cases, and chromosomal abnormalities were detected in 18 (100%) of the technically successful cases. Deletion 13q14.3 was most frequent (10 [56%]; isolated in 8 and with other abnormalities in 2), followed by trisomy 12 (5 [28%]), deletion 11q22.3 (4/16 [25%]), 14q32 (IGH@) translocation (3 [17%]), and deletion 17p13.1 (1/16 [6%]). One case with IGH@ translocation showed a BCL2 translocation partner. No cases showed 6q23 deletion. Results of this FISH panel performed on 42 additional peripheral blood (PB)/bone marrow (BM) CLL specimens were similar except for a significantly greater frequency of deletion 13q14.3 in combination with other aberrations. Cytogenetic FISH studies using paraffin-embedded tissue biopsy specimens in CLL/SLL had a high yield and, with 1 exception, demonstrated a profile similar to cases diagnosed in PB/BM.

Expression of HGAL in primary cutaneous large B-cell lymphomas: evidence for germinal center derivation of primary cutaneous follicular lymphoma

The classification of primary cutaneous large B-cell lymphoma (PCLBCL) is based on standard morphology, immunohistochemistry, and clinical presentation. There are two major subtypes in the current WHO-EORTC classification: follicle center lymphoma and diffuse large B-cell lymphoma, leg-type (DLBCL-LT). The goals of this study were to examine a series of DLBCLs to determine (1) whether the immunohistochemical paradigm of germinal center B-cell and non-germinal center B-cell types of systemic DLBCL could be applied to PCLBCL; (2) whether application of the newly described germinal center B-cell marker, human germinal center-associated lymphoma (HGAL) also discriminates between these types as a further support for germinal center B-cell origin for primary cutaneous center lymphoma; and (3) whether any of these biologic markers were of prognostic significance. To this end, 32 cases of diffuse PCLBCL (22 primary cutaneous follicular center lymphomas and 10 DLBCL-LT) were classified based on the WHO-EORTC criteria and studied for expression of CD20, BCL2, BCL6, CD10, MUM-1, and HGAL by immunohistochemistry. Results were correlated with clinical features. HGAL and BCL6 expression and germinal center B-cell phenotype were associated with primary cutaneous follicular center lymphoma. The combination of HGAL and BCL6 positivity had the highest sensitivity (88%) and specificity (100%) for predicting subtype compared to either marker alone. Both HGAL and BCL6 were associated with the germinal center B-cell phenotype. The correlation of HGAL expression with the germinal center B-cell phenotype demonstrates the role of this marker in the classification of cutaneous large B-cell lymphomas. BCL6 expression was the only immunohistochemical marker associated with overall survival. Characterizing PCLBCLs with markers of B-cell maturation stage is a useful framework for studying, classifying, and clinically stratifying these lymphomas.

Gene expression profiling of Epstein-Barr virus-positive and -negative monomorphic B-cell posttransplant lymphoproliferative disorders

Although most posttransplant lymphoproliferative disorders (PTLD) are related to Epstein-Barr virus (EBV) infection, approximately 20% lack detectable EBV (EBV-). It is uncertain whether the latter cases are truly distinct from EBV+ PTLD or possibly relate to another infectious agent. This study used gene expression profiling to further investigate the relationship between EBV+ and EBV- monomorphic B-cell PTLD, and to search for clues to their pathogenesis. Affymetrix HU133A GeneChips were used to compare 4 EBV+ and 4 EBV- cases of monomorphic B-cell PTLD. Hierarchical clustering successfully distinguished the EBV+ and EBV- groups. Relative to EBV- PTLD, 54 transcripts were over-expressed in EBV+ PTLD. The transcripts identified included IRF7 (a known regulator of EBV LMP1 expression), EBI2 (EBV-induced gene 2), and 3 that are interferon induced (MX1, IFITM1, and IFITM3). In addition, the EBV+ group contained 232 transcripts decreased relative to the EBV- group, including changes concordant with those previously reported after EBV infection of cultured B-cell lines. In summary, in a small group of monomorphic B-cell PTLD, EBV+ cases demonstrated a subset of gene expression changes associated with EBV infection of B cells. By contrast, EBV- PTLD lacked viral-associated changes suggesting that they are biologically distinct.

T-cell and NK-cell posttransplantation lymphoproliferative disorders

Posttransplantation lymphoproliferative disorders (PTLDs) of T-cell or natural killer (NK)-cell origin are an uncommon heterogeneous group of lymphoid proliferations that fulfill the criteria for one of the T- or NK-cell lymphomas/leukemias. This report summarizes 130 T/NK-cell PTLDs reported in the literature or presented at the Society for Hematopathology/European Association for Haematopathology Workshop on T/NK-cell malignancies. The T/NK-cell PTLDs occur at a median of 66 months following transplantation and are usually extranodal. The most common types reported are peripheral T-cell lymphoma, unspecified, and hepatosplenic T-cell lymphoma. Approximately one third are Epstein-Barr virus (EBV)+. The median survival is 6 months. EBV+ cases have a significantly longer survival than EBV- cases, even when indolent T-cell large granular lymphocytic leukemias are included among the EBV- cases. Many T/NK-cell PTLDs have been treated with chemotherapy, often together with decreased immunosuppression, but there are infrequent patients who have done well without chemotherapy or radiation.

Classical Hodgkin's lymphoma presenting as a testicular mass: report of a case

Hodgkin's lymphoma almost always presents with lymphadenopathy. Presentation with extranodal disease is quite unusual, although Hodgkin's lymphoma is known to occasionally involve extranodal sites. However, no well-documented cases of testicular Hodgkin's lymphoma have been described. We report the case of a 52-year-old man who presented with a left testicular mass; orchiectomy revealed morphologic and immunophenotypic features typical of classical Hodgkin's lymphoma, nodular sclerosis type.

JAK2 V617F mutation in patients with catastrophic intra-abdominal thromboses

Catastrophic intra-abdominal thrombosis can result from a variety of prothrombotic states, including polycythemia vera and essential thrombocythemia, both of which are frequently associated with an acquired mutation (V617F) in the JAK2 gene. To assess the prevalence and clinical implications of this mutation in the setting of intra-abdominal thrombosis, JAK2 V617F genotyping was performed in 42 patients who had catastrophic intra-abdominal thromboses resulting in visceral transplants. The prevalence of V617F was compared with that of other prothrombotic states for which molecular testing is routinely performed. V617F mutations were detected in 7 patients (17%), who were not distinguishable on the basis of their peripheral blood cell counts. The median posttransplantation survival of V617F+ patients was 17.5 months, compared with 116.4 months for the V617F- patients (ratio, 6.6; 95% confidence interval, 6.3-7.0). These results highlight the diagnostic usefulness of JAK2 V617F testing in this setting and underscore the clinical significance of a positive result.

Extranodal Marginal Zone B-cell Lymphomas of the Ocular Adnexa

Extranodal marginal zone B-cell lymphomas of MALT type (MALT lymphomas) show site-dependent variations in their morphologic, phenotypic, and/or cytogenetic findings. This report describes a comprehensive analysis of 34 ocular adnexa MALT lymphomas, including interphase fluorescence in situ hybridization for MALT lymphoma-associated cytogenetic abnormalities and polymerase chain reaction for Chlamydia psittaci, which has recently been suggested to be associated with ocular adnexa lymphomas. A typical morphologic pattern was identified in 79% of cases, while overtly monocytoid cytology (12%), predominantly plasmacytic features (9%), and lymphoepithelial lesions (3%) were uncommon. Aberrant CD43 or CD5 expression was also uncommon (12% and 3%, respectively). Plasmacytic differentiation (41%) was associated with stage IV disease (P=0.036) and gains of chromosomes 3 and/or 18q (P=0.021) (79%). +3 was more frequent in the orbit than in lacrimal gland or conjunctiva (P=0.005). Each of 31 cases was negative for MALT1 translocations. IGH translocations were identified in 3 cases (10%), although the translocation partner gene could not be identified. Polymerase chain reaction assays targeting species-specific regions within the C. psittaci omp1 and omp2 genes were negative in each of 30 cases. This study identifies the characteristic morphologic, phenotypic, and cytogenetic findings in ocular adnexa MALT lymphoma, including a subset differing from those arising at other anatomic sites. The frequent presence of +3 and/or +18q suggests that these abnormalities may contribute to lymphomagenesis. The lack of C. psittaci in this series, in contrast to some prior reports, indicates that there may also be geographic heterogeneity in the pathogenesis of ocular adnexa MALT lymphoma.

Nodal aggressive B-cell lymphomas: a diagnostic approach

The diffuse aggressive B-cell lymphomas, as recognised in the 2001 WHO classification, represent a clinically and biologically heterogeneous group of neoplasms that require very different therapeutic approaches and have very different outcomes. They should be diagnosed using a multiparameter approach that emphasises morphological and immunophenotypic studies, and in at least some cases, relies on cytogenetic and/or genotypic studies. Incorporation of clinical data may be important as well. There is also current interest in going beyond the basic diagnosis and providing pathological prognostic information when possible. Whereas the diagnosis of some cases will be relatively easy, the differential diagnosis in others is very difficult, with some cases in a grey zone between two different well defined categories.