Ellen D. McPhail

Novel immunophenotypic features of marrow lymphoplasmacytic lymphoma and correlation with Waldenström's macroglobulinemia

Lymphoplasmacytic lymphoma involving the bone marrow can be difficult to diagnose, and pathological features that predict the presence of associated Waldenströms macroglobulinemia have yet to be identified. To address these issues, marrow histology, immunohistochemistry, and flow cytometry were studied from 35 lymphoplasmacytic lymphoma cases that had comprehensive clinical assessment for Waldenströms macroglobulinemia. In all cases, the plasma cells were analyzed by a novel 6-color flow method. Both immunohistochemistry and flow cytometry were useful in identifying the lymphoid and plasmacytic disease components. In 19 cases, immunohistochemistry revealed an earlier unrecognized pattern of plasma cell infiltration in which they were physically separate from the lymphoid infiltrates. B-cell flow cytometry revealed monotypic cells in 96% of the cases. Approximately half of these were CD5 and/or CD23 positive, although none had features of chronic lymphocytic leukemia, and none of the B cells had flow cytometric features suggesting plasmacytic differentiation. In contrast, highly sensitive 6-color plasma cell flow cytometry revealed monotypic cells in 32 of the 35 cases; in 20 cases, the pattern of CD38 and CD138 coexpression detected was identical to that seen in plasma cell malignancies such as multiple myeloma. In 18 of these 20 lymphoplasmacytic lymphoma cases, these plasma cells were CD19 positive, distinguishing them from those of true plasma cell neoplasms, which are CD19 negative. It is interesting that the two lymphoplasmacytic lymphoma cases with CD19-negative plasma cells had an IgG isotype serum paraprotein. Apart from this, no other pathological correlates of the clinical or laboratory features of symptomatic Waldenströms macroglobulinemia were identified.

Expression of MALT1 oncogene in hematopoietic stem/progenitor cells recapitulates the pathogenesis of human lymphoma in mice

Chromosomal translocations involving the MALT1 gene are hallmarks of mucosa-associated lymphoid tissue (MALT) lymphoma. To date, targeting these translocations to mouse B cells has failed to reproduce human disease. Here, we induced MALT1 expression in mouse Sca1+Lin− hematopoietic stem/progenitor cells, which showed NF-κB activation and early lymphoid priming, being selectively skewed toward B-cell differentiation. These cells accumulated in extranodal tissues and gave rise to clonal tumors recapitulating the principal clinical, biological, and molecular genetic features of MALT lymphoma. Deletion of p53 gene accelerated tumor onset and induced transformation of MALT lymphoma to activated B-cell diffuse large-cell lymphoma (ABC-DLBCL). Treatment of MALT1-induced lymphomas with a specific inhibitor of MALT1 proteolytic activity decreased cell viability, indicating that endogenous Malt1 signaling was required for tumor cell survival. Our study shows that human-like lymphomas can be modeled in mice by targeting MALT1 expression to hematopoietic stem/progenitor cells, demonstrating the oncogenic role of MALT1 in lymphomagenesis. Furthermore, this work establishes a molecular link between MALT lymphoma and ABC-DLBCL, and provides mouse models to test MALT1 inhibitors. Finally, our results suggest that hematopoietic stem/progenitor cells may be involved in the pathogenesis of human mature B-cell lymphomas.

Genome-Wide Analysis Uncovers Novel Recurrent Alterations in Primary Central Nervous System Lymphomas

Purpose: Primary central nervous system lymphoma (PCNSL) is an aggressive non-Hodgkin lymphoma confined to the central nervous system. Whether there is a PCNSL-specific genomic signature and, if so, how it differs from systemic diffuse large B-cell lymphoma (DLBCL) is uncertain. Experimental Design: We performed a comprehensive genomic study of tumor samples from 19 immunocompetent PCNSL patients. Testing comprised array-comparative genomic hybridization and whole exome sequencing. Results: Biallelic inactivation of TOX and PRKCD was recurrently found in PCNSL but not in systemic DLBCL, suggesting a specific role in PCNSL pathogenesis. In addition, we found a high prevalence of MYD88 mutations (79%) and CDKN2A biallelic loss (60%). Several genes recurrently affected in PCNSL were common with systemic DLBCL, including loss of TNFAIP3, PRDM1, GNA13, TMEM30A, TBL1XR1, B2M, CD58, activating mutations of CD79B, CARD11, and translocations IgH-BCL6. Overall, B-cell receptor/Toll-like receptor/NF-κB pathways were altered in >90% of PNCSL, highlighting its value for targeted therapeutic approaches. Furthermore, integrated analysis showed enrichment of pathways associated with immune response, proliferation, apoptosis, and lymphocyte differentiation. Conclusions: In summary, genome-wide analysis uncovered novel recurrent alterations, including TOX and PRKCD, helping to differentiate PCNSL from systemic DLBCL and related lymphomas. Clin Cancer Res; 21(17); 3986–94. ©2015 AACR.

Detection of human papilloma virus and p16 expression in high-grade adenoid cystic carcinoma of the head and neck

Squamous cell carcinoma of the head and neck, particularly basaloid squamous cell carcinoma, may be difficult to distinguish from high-grade adenoid cystic carcinoma. Evidence of human papilloma virus (HPV) infection, particularly HPV 16, is frequently found in non-keratinizing oropharyngeal squamous cell carcinoma. Immunoreactivity for p16, a surrogate marker for HPV infection, often parallels the HPV infection status in oropharyngeal squamous cell carcinoma. However, the incidence and correlation between p16 expression and HPV infection in high-grade adenoid cystic carcinoma is unknown. Sixteen cases of high-grade adenoid cystic carcinoma, three cases of dedifferentiated adenoid cystic carcinoma and eight cases of low-/intermediate-grade adenoid cystic carcinoma were identified for inclusion in the study. All cases were tested by immunohistochemistry for p16 expression and in situ hybridization for high- and low-risk HPV. Eight cases (100%) of low-to-intermediate-grade adenoid cystic carcinoma were focally positive for p16, all of which were negative for HPV. In all, 14 of 16 cases (88%) of high-grade adenoid cystic carcinoma and three cases (100%) of dedifferentiated adenoid cystic carcinoma were positive for p16; strong and diffuse staining was noted in three cases (3 of 19, 16%). Two cases (11%) of high-grade adenoid cystic carcinoma, which were also diffusely positive for p16, showed the presence of high-risk HPV. These findings suggest that the presence of HPV infection in high-grade adenoid cystic carcinoma is infrequent, even in the presence of p16 immunostaining. Nevertheless, HPV positivity should not be used to exclude the possibility of high-grade adenoid cystic carcinoma when the differential diagnosis includes squamous cell carcinoma. Moreover, although p16 overexpression is often used as a surrogate marker for HPV in squamous cell carcinoma, it cannot be used in this manner in high-grade adenoid cystic carcinoma.

Coexisting follicular and mantle cell lymphoma with each having an in situ component: A novel, curious, and complex consultation case of coincidental, composite, colonizing lymphoma.

A diagnosis of composite lymphoma is typically prompted by the observation of morphologic discordance. We present a case of a spleen revealing histologic features of follicular lymphoma, without any indication of a second lymphoma. Immunohistochemical stains supported this diagnosis and showed the follicular lymphoma to be BCL2-. However, these studies revealed 2 additional unexpected findings: cyclin D1+ mantle zone cells surrounding neoplastic and reactive follicles (indicative of in situ mantle cell lymphoma) and BCL2-bright, histologically nonneoplastic follicles (indicative of in situ follicular lymphoma). ImmunoFISH and microdissection and polymerase chain reaction analysis documented the clonal nature of the cyclin D1+ mantle zones and illustrated clonal independence from the follicular lymphoma. This case illustrates an uncommon and unusual composite follicular and mantle cell lymphoma, with the follicular lymphoma accompanied by an in situ component, whereas the only manifestation of the mantle cell lymphoma was in situ.

Splenic marginal zone lymphoma: characterization of 7q deletion and its value in diagnosis

The diagnosis of splenic marginal zone lymphoma (SMZL) is frequently a challenge, due to its lack of specific histological features and immunophenotypic markers, and the existence of other poorly characterized splenic lymphomas defying classification. Moreover, the clinical outcome of SMZL is variable, with 30% of cases pursuing an aggressive clinical course, the prediction of which remains problematic. Thus, there is a real need for biomarkers in the diagnosis and prognostication of SMZL. To search for genetic markers, we comprehensively investigated the genomic profile, TP53 abnormalities, and immunoglobulin heavy gene (IGH) mutation in a large cohort of SMZLs. 1 Mb resolution array comparative genomic hybridization (aCGH) on 25 SMZLs identified 7q32 deletion (44%) as the most frequent copy number change, followed by gains of 3q (32%), 8q (20%), 9q34 (20%), 12q23–24 (8%), and chromosome 18 (12%), and losses of 6q (16%), 8p (12%), and 17p (8%). High‐resolution chromosome 7 tile‐path aCGH on 17 SMZLs with 7q32 deletion identified by 1 Mb aCGH or interphase FISH screening mapped the minimal common deletion to a 3 Mb region at 7q32.1–32.2. Although it is not yet possible to identify the genes targeted by the deletion, interphase FISH screening showed that the deletion was seen in SMZL (19/56 = 34%) and splenic B‐cell lymphoma/leukaemia unclassifiable (3/9 = 33%), but not in 39 cases of other splenic lymphomas including chronic lymphocytic leukaemia (n = 14), hairy cell leukaemia (4), mantle cell lymphoma (12), follicular lymphoma (6), and others. In SMZL, 7q32 deletion was inversely correlated with trisomy 18, but not associated with other copy number changes, TP53 abnormalities, or IGH mutation status. None of the genetic parameters examined showed significant and independent association with overall or event‐free survival. In conclusion, 7q32 deletion is a characteristic feature of SMZL, albeit seen in isolated cases of splenic B‐cell lymphoma/leukaemia unclassifiable, and its detection may help the differential diagnosis of splenic B‐cell lymphomas. Copyright

Clonally related follicular lymphomas and langerhans cell neoplasms: Expanding the spectrum of transdifferentiation

The traditional model of hematopoiesis is based on unidirectional maturation of hematopoietic precursors into lineage-committed cells. However, recent studies indicate that mature B lymphocytes may demonstrate significant lineage plasticity. We and others have reported transdifferentiation of follicular lymphomas (FLs) into clonally related histiocytic/dendritic cell neoplasms. Here, we describe 2 patients with FL who developed clonally related Langerhans cell neoplasms. The first was a 52-year-old man diagnosed with FL, grade 1. He received immunochemotherapy and had stable disease for 8 years. He then developed increasing lymphadenopathy, and lymph node biopsy showed Langerhans cell sarcoma with no evidence of FL. The second patient was a 77-year-old woman who presented with lymphadenopathy, an abdominal mass, and pulmonary nodules. Lymph node biopsy showed both Langerhans cell histiocytosis and minimal involvement by FL, grade 1. In each case, a combination of immunoglobulin gene rearrangement and fluorescence in situ hybridization studies provided evidence to support a clonal relationship between the FL and Langerhans cell neoplasm. These cases provide striking examples of neoplastic transdifferentiation and expand the spectrum of lesions clonally identical to otherwise typical FL. Awareness of this phenomenon may aid in diagnosis when histologically dissimilar tumors arise synchronously or metachronously in patients with lymphoma.

t(X;14)(p11;q32) in MALT lymphoma involving GPR34 reveals a role for GPR34 in tumor cell growth

Genetic aberrations, including trisomies 3 and 18, and well-defined IGH translocations, have been described in marginal zone lymphomas (MZLs); however, these known genetic events are present in only a subset of cases. Here, we report the cloning of an IGH translocation partner on chromosome X, t(X;14)(p11.4;q32) that deregulates expression of an poorly characterized orphan G-protein-coupled receptor, GPR34. Elevated GPR34 gene expression was detected independent of the translocation in multiple subtypes of non-Hodgkin lymphoma and distinguished a unique molecular subtype of MZL. Increased expression of GPR34 was also detected in tissue from brain tumors and surface expression of GPR34 was detected on human MZL tumor cells and normal immune cells. Overexpression of GPR34 in lymphoma and HeLa cells resulted in phosphorylation of ERK, PKC, and CREB; induced CRE, AP1, and NF-κB-mediated gene transcription; and increased cell proliferation. In summary, these results are the first to identify a role for a GPR34 in lymphoma cell growth, provide insight into GPR34-mediated signaling, identify a genetically unique subset of MZLs that express high levels of GPR34, and suggest that MEK inhibitors may be useful for treatment of GPR34-expressing tumors.

An integrated genomic and expression analysis of 7q deletion in splenic marginal zone lymphoma.

Splenic marginal zone lymphoma (SMZL) is an indolent B-cell lymphoproliferative disorder characterised by 7q32 deletion, but the target genes of this deletion remain unknown. In order to elucidate the genetic target of this deletion, we performed an integrative analysis of the genetic, epigenetic, transcriptomic and miRNomic data. High resolution array comparative genomic hybridization of 56 cases of SMZL delineated a minimally deleted region (2.8 Mb) at 7q32, but showed no evidence of any cryptic homozygous deletion or recurrent breakpoint in this region. Integrated transcriptomic analysis confirmed significant under-expression of a number of genes in this region in cases of SMZL with deletion, several of which showed hypermethylation. In addition, a cluster of 8 miRNA in this region showed under-expression in cases with the deletion, and three (miR-182/96/183) were also significantly under-expressed (P<0.05) in SMZL relative to other lymphomas. Genomic sequencing of these miRNA and IRF5, a strong candidate gene, did not show any evidence of somatic mutation in SMZL. These observations provide valuable guidance for further characterisation of 7q deletion.

CD5+ B-cell lymphoproliferative disorders: Beyond chronic lymphocytic leukemia and mantle cell lymphoma

CD5 positivity in B-cell lymphoproliferative disorders (LPD) is usually considered characteristic of either chronic lymphocytic leukemia (CLL) or mantle cell lymphoma (MCL). However, other neoplastic B-LPDs may express CD5, albeit infrequently. In this study we have reviewed the tissue pathology of CD5+ B-LPDs that do not fulfill diagnostic criteria for CLL or MCL on flow cytometric studies of peripheral blood or bone marrow. Our results indicate that although CD5 positivity is most commonly associated with CLL and MCL, a significant minority of cases do not fall into these two categories. Phenotypically unusual CLL, marginal zone lymphoma and lymphoplasmacytic lymphoma were the most common diagnoses in this group of patients. Applying strict flow cytometry criteria, using genetic studies, and deferring to a lymph node/tissue diagnosis in non-classical cases are critical for accurate diagnosis and classification of CD5+ B-cell LPD.