Marginal zone lymphomas with plasmacytic differentiation and related disorders

Phosphatidylserine phospholipase A1 enables GPR34-dependent immune cell accumulation in the peritoneal cavity

The peritoneal cavity (PerC) is an important site for immune responses to infection and cancer metastasis. Yet few ligand-receptor axes are known to preferentially govern immune cell accumulation in this compartment. GPR34 is a lysophosphatidylserine (lysoPS)-responsive receptor that frequently harbors gain-of-function mutations in mucosa-associated B cell lymphoma. Here, we set out to test the impact of a GPR34 knock-in (KI) allele in the B-lineage. We report that GPR34 KI promotes the PerC accumulation of plasma cells (PC) and memory B cells (MemB). These KI cells migrate robustly to lysoPS ex vivo, and the KI allele synergizes with a Bcl2 transgene to promote MemB but not PC accumulation. Gene expression and labeling studies reveal that GPR34 KI enhances PerC MemB proliferation. Both KI PC and MemB are specifically enriched at the omentum, a visceral adipose tissue containing fibroblasts that express the lysoPS-generating PLA1A enzyme. Adoptive transfer and chimera experiments revealed that KI PC and MemB maintenance in the PerC is dependent on stromal PLA1A. These findings provide in vivo evidence that PLA1A produces lysoPS that can regulate GPR34-mediated immune cell accumulation at the omentum.

Histological criteria for selecting patients who need clonality test for non-gastric MALT lymphoma diagnosis

The histological diagnosis of extranodal marginal zone lymphoma of the mucosa-associated lymphoid tissue (MALT lymphoma) is difficult for pathologists. Recently, digital pathology systems have been widely used to provide tools that can objectively measure lesions on slides. In this study, we measured the extent of marginal zone expansion in suspected MALT lymphoma cases and compared the results with those of a molecular clonality test. In total, 115 patients who underwent an IGH gene rearrangement test for suspected MALT lymphoma were included in this study. All cases were histologically classified into three patterns; "small lymphoid aggregates with no germinal center (Pattern 1)," "lymphoid follicles with germinal center (Pattern 2)" and " fused marginal zone or diffuse small lymphocytic proliferation (Pattern 3)." The proportions of monoclonality in Pattern 1, 2, and 3 were 25.0%, 55.0%, and 97.9%, respectively. The ratios of marginal zone thickness to germinal center diameter and entire lymphoid follicle area to germinal center area were measured in Pattern 2 cases using a digital pathology system. Combining the width cutoff of 1.5 and the areal cutoff of 3.5, the sensitivity, specificity, positive predictive value, and negative predictive value for MALT lymphoma were 96.97%, 70.37%, 80.00%, and 95.00%, respectively. In conclusion, through objective measurement of the marginal zone, suspected cases of MALT lymphoma requiring a molecular clonality test can be effectively selected.

The clinical significance of increased large cells in marginal zone lymphoma

Marginal zone lymphoma (MZL) is a primary, indolent small B-cell lymphoma. Subtypes include nodal, splenic, and those of extranodal mucosa-associated lymphoid tissue (MALT). These are slow growing and generally exhibit low rates of transformation to diffuse large B-cell lymphoma (DLBCL). At initial diagnosis, there can be an increase in large cells (LCs) that does not meet criteria for DLBCL. Prior studies have noted this finding, but the clinical significance of these LCs has not been well established. A total of 161 cases of MZL from 1994 to 2021 were evaluated, including all subtypes. There were 33 cases with increased LCs (>10 LCs per high-power field [hpf]), with the majority containing >15 LCs/hpf (28/33) and 128 cases without increased LCs. Cases with increased LCs were significantly more likely to have a Ki-67 proliferation index of ≥30% (P < .0001). Overall survival was not significantly different between the groups but progression-free survival was significantly worse in the LC group (P < .0001). MZL with increased LCs was also associated with a higher stage at diagnosis (P = .0035), was more likely to transform to DLBCL (P = .0016), and had a greater frequency of relapse (P < .0001). Subgroup analysis showed that both nodal and MALT LC groups had a worse progression-free survival and a higher rate of relapse than their standard nodal and MALT lymphoma counterparts, but only within the MALT subgroup did the LC cases present at a higher stage and have a higher rate of transformation to DLBCL than the standard cases. Although larger studies are needed for validation, these results suggest that the presence of LCs in MZL may serve as a useful prognostic indicator and potentially help guide clinical decision-making.

Hematological entities with plasmacytic differentiation: a case report

INTRODUCTION

Plasmacytoma, a localized tumor of monoclonal plasma cells without any clinical, radiological or physical evidence of plasma cell neoplasm (PCN), is a rare entity that accounts for 1% of PCN. Immunoglobulin M (IgM) extramedullary plasmacytoma of mediastinal region has never been reported and is a diagnostic challenge considering other differential diagnoses.

CASE PRESENTATION

We present the case of a 51-year-old African-American female with progressively increasing cough, dyspnea, and dysphagia for 6 months with a computed tomography (CT) scan revealing a subcarinal mass. The histopathological analysis of the mass reveals a diagnosis of lymphoma with plasma cell differentiation, with a differential of lymphoplasmacytic lymphoma and plasma cell neoplasm. The lymphoma panel via next-generation sequencing (NGS) and a myeloma-targeted fluorescent in situ hybridization (FISH) panel confirmed the diagnosis of IgM extramedullary plasmacytoma, an entity of rare occurrence. Treatment with radiation led to complete regression of the plasmacytoma with normal blood work-up.

CONCLUSIONS

This report describes the challenges of diagnosing IgM extramedullary plasmactyoma. Our case report highlights the importance of cytogenetics and NGS in establishing a correct diagnosis that indeed has prognostic and therapeutic implications.

Impact of detectable monoclonal protein at diagnosis on outcomes in marginal zone lymphoma: a multicenter cohort study

Given the paucity of data surrounding the prognostic relevance of monoclonal paraprotein (M-protein) in marginal zone lymphoma (MZL), we sought to evaluate the impact of detecting M-protein at diagnosis on outcomes in patients with MZL in a large retrospective cohort. The study included 547 patients receiving first-line therapy for MZL. M-protein was detectable at diagnosis in 173 (32%) patients. There was no significant difference in the time from diagnosis to initiation of any therapy (systemic and local) between the M-protein and no M-protein groups. Patients with M-protein at diagnosis had significantly inferior progression-free survival (PFS) compared with those without M-protein at diagnosis. After adjusting for factors associated with inferior PFS in univariate models, presence of M-protein remained significantly associated with inferior PFS (hazard ratio, 1.74; 95% confidence interval, 1.20-2.54; P = .004). We observed no significant difference in the PFS based on the type or quantity of M-protein at diagnosis. There were differential outcomes in PFS based on the first-line therapy in patients with M-protein at diagnosis, in that, those receiving immunochemotherapy had better outcomes compared with those receiving rituximab monotherapy. The cumulative incidence of relapse in stage 1 disease among the recipients of local therapy was higher in the presence of M-protein; however, this did not reach statistical significance. We found that M-protein at diagnosis was associated with a higher risk of histologic transformation. Because the PFS difference related to presence of M-protein was not observed in patients receiving bendamustine and rituximab, immunochemotherapy may be a preferred approach over rituximab monotherapy in this group and needs to be explored further.

Leukemic Involvement Is a Common Feature in Waldenström Macroglobulinemia at Diagnosis

Waldenström Macroglobulinemia (WM) is a lymphoplasmacytic lymphoma with bone marrow (BM) involvement and IgM monoclonal gammopathy. To date, no studies have focused specifically on peripheral blood (PB) involvement. In this study, 100 patients diagnosed with WM according to the World Health Organization (WHO) criteria were included based on the demonstration of MYD88mut in BM and the availability of PB multiparametric flow cytometry (MFC) analysis. Leukemic involvement by MFC was detected in 50/100 patients. A low percentage of mature small lymphocytes in PB smears was observed in only 15 cases. MYD88mut by AS-qPCR was detected in PB in 65/100 cases. In cases with leukemic expression by MFC, MYD88mut was detected in all cases, and IGH was rearranged in 44/49 cases. In 21/50 patients without PB involvement by MFC, molecular data were consistent with circulating disease (MYD88mut by AS-qPCR 3/50, IGH rearranged 6/50, both 12/50). Therefore, PB involvement by standard techniques was detected in 71/100 patients. MYD88mut was detected in PB by dPCR in 9/29 triple negative cases. Overall, 80% of the patients presented PB involvement by any technique. Our findings support the role of PB MFC in the evaluation of patients with IgM monoclonal gammopathy and provide reliable information on correlation with molecular features. The development of a feasible MFC assay may stand as an objective tool in the classification of mature B cell neoplasms presenting with IgM monoclonal gammopathy.

Study of the Utility of Myeloid Cell Nuclear Differentiation Antigen (MNDA) in the Diagnosis of Marginal Zone Lymphoma

Myeloid cell nuclear differentiation antigen (MNDA) is normally expressed on myelomonocytic cells and a subset of B lymphocytes. It was found to be differentially expressed between nodal marginal zone lymphoma (MZL) and follicular lymphoma (FL). However, MNDA has not been widely used as a diagnostic marker in clinical practice. To validate its utility, we studied the expression of MNDA by immunohistochemistry in 313 cases of small B-cell lymphomas. Our results showed that MNDA was positive in 77.9% of MZL, 21.9% of mantle cell lymphoma, 28.9% of small lymphocytic lymphoma/chronic lymphocytic leukemia, 2.6% of FL, and 25% of lymphoplasmacytic lymphoma. MNDA positivity varied from 68.0% to 84.0% among the 3 MZL subtypes, with extranodal MZL having the highest percentage. There was a statistically significant difference in MNDA expression between MZL and FL, mantle cell lymphoma, small lymphocytic lymphoma/chronic lymphocytic leukemia, or lymphoplasmacytic lymphoma. CD43 expression was slightly more frequent in MNDA-negative MZL than in MNDA-positive MZL. Combined use of CD43 and MNDA improved the diagnostic sensitivity for MZL from 77.9% to 87.8%. There was a trend of positive correlation between MNDA and p53 in MZL. In conclusion, MNDA is preferentially expressed in MZL among small B-cell lymphomas and it is a useful marker for the differentiation of MZL and FL.

Gastrointestinal, Hepatic and Pancreatobiliary Involvement by Plasma Cell Neoplasms: Clinicopathologic Correlations in a Retrospective Cohort of 116 Cases

AIMS

Plasma cell neoplasms (PCNs) may involve the gastrointestinal (GI) tract in two forms: plasmacytoma (PC), an isolated lesion which lacks marrow involvement, and extramedullary myeloma (EMM). However, previous literature on PCNs involving the GI tract, liver and pancreas is limited. We evaluated the clinicopathologic features of the largest series of GI PCNs to date.

METHODS AND RESULTS

Six institutional archives were searched for GI, liver and pancreas cases involved by PCNs. Medical records were reviewed for clinical and imaging features. Histopathologic features evaluated included involved organ, tumor grade and marrow involvement. Overall, 116 cases from 102 patients were identified. Tumors most presented as incidental findings (29%). The liver was most involved (47%), and masses/polyps (29%) or ulcers (21%) were most common findings. Most cases had high-grade morphology (55%). The majority (74%) of GI PCNs were classified as EMM due to the presence of marrow involvement at some point during the disease course, occurring within a year of marrow diagnosis in 46% of patients. PC was classified in 26% of patients due to the lack of marrow involvement. Most (70%) patients died from disease within 10 years (median 14.1) of diagnosis and more than half (58%) died within 6 months.

CONCLUSION

PC and EMM involving the GI tract, liver and pancreas have a wide range of clinicopathologic presentations. Tumors may occur virtually anywhere in the GI tract or abdomen and may precede the diagnosis of marrow involvement. Both GI PC and EMM are associated with a poor prognosis.

Extranodal MALT Lymphoma in the Oral Cavity: A Series of Three Cases with Review of Literature

BACKGROUND

Diagnosis of MALT lymphoma in the oral cavity is challenging. There is a great overlap in the histopathologic, immuno-histochemical and molecular features of MALT lymphoma with reactive lymphoid proliferations. The literature shows a very few case reports of primary MALT lymphoma of oral cavity.

METHODS

We discuss the histopathologic, immuno-histochemical, cytogenetic features, treatment and behavior of 3 cases of primary MALT lymphoma oral cavity along with review of literature.

RESULTS

The age ranged from 40 to 57 years (male to female ratio = 2:1). The sites involved were hard palate, bilateral gingivobuccal sulcus and right buccal mucosa. The most common histology was centrocyte-like (2 cases). Lymphoepithelial lesions were absent. On immunohistochemistry, all tumors showed diffuse strong CD20 and bcl2 expression with strong and diffuse MNDA staining in one case. IgH; MALT1 translocation was not seen in any of these cases. One patient received local radiotherapy, one received steroids; while the case 3 received RCHOP (Rituximab, cyclophosphamide, hydroxydaunorubicin hydrochloride, vincristine and prednisone) chemotherapy. Two patients had complete remission while one had recurrence.

CONCLUSION

MALT lymphoma of oral cavity shows a wide spectrum of morphology with presence of transformed cells, that may lead to misdiagnosis of DLBL. Treatment guidelines are not well established but a tendency to excise MALT lymphomas of oral cavity has been observed. Nevertheless, MALT lymphoma of oral cavity appears to be an indolent disease.

CD5-Negative, CD10-Negative Low-Grade B-Cell Lymphoproliferative Disorders of the Spleen

CD5-negative, CD10-negative low-grade B-cell lymphoproliferative disorders (CD5-CD10-LPD) of the spleen comprise a fascinating group of indolent, neoplastic, mature B-cell proliferations that are essential to accurately identify but can be difficult to diagnose. They comprise the majority of B-cell LPDs primary to the spleen, commonly presenting with splenomegaly and co-involvement of peripheral blood and bone marrow, but with little to no involvement of lymph nodes. Splenic marginal zone lymphoma is one of the prototypical, best studied, and most frequently encountered CD5-CD10-LPD of the spleen and typically involves white pulp. In contrast, hairy cell leukemia, another well-studied CD5-CD10-LPD of the spleen, involves red pulp, as do the two less common entities comprising so-called splenic B-cell lymphoma/leukemia unclassifiable: splenic diffuse red pulp small B-cell lymphoma and hairy cell leukemia variant. Although not always encountered in the spleen, lymphoplasmacytic lymphoma, a B-cell lymphoproliferative disorder consisting of a dual population of both clonal B-cells and plasma cells and the frequent presence of the MYD88 L265P mutation, is another CD5-CD10-LPD that can be seen in the spleen. Distinction of these different entities is possible through careful evaluation of morphologic, immunophenotypic, cytogenetic, and molecular features, as well as peripheral blood and bone marrow specimens. A firm understanding of this group of low-grade B-cell lymphoproliferative disorders is necessary for accurate diagnosis leading to optimal patient management.

A case report of primary cutaneous marginal zone B-cell lymphoma with mastocytosis

A 53-year-old man presented with asymptomatic, dusky reddish nodules on his trunk, which had persisted for 7 years. Histological findings showed nodular to diffuse dermal infiltration of lymphocytes with irregular nuclei, eosinophils, plasma cells, and mast cells. CD20 revealed patch positivity. Periphery of lymphoid follicles showed BCL-2 positivity and BCL-6 positivity focally at the center. CD30 and toluidine blue staining showed positivity, and several mast cells were confirmed. The immunoglobulin heavy chain gene rearrangement result showed B-cell monoclonality. The patient’s condition was diagnosed as cutaneous marginal zone B-cell lymphoma, plasmacytoid type with mastocytosis. Primary cutaneous marginal zone B-cell lymphoma is an indolent lymphoma with a tendency for local recurrence. In the specimen obtained from our patient, multiple mast cells were observed. Primary cutaneous marginal zone B-cell lymphoma with prominent mastocytosis is rare and there are a few reported cases. Therefore, this case is worth reporting for its rarity and for the purpose of reminding mastocytosis in primary cutaneous marginal zone B-cell lymphoma.

Monotypic Plasma Cell Proliferation of Uncertain Clinical Significance Mimicking Interstitial Cystitis: An Early Lesion of MALT Lymphoma?

We prospectively studied our institutional experience of bladder extranodal marginal zone (mucosa-associated lymphoid tissue [MALT]) lymphoma including bladder biopsies in which the possibility of MALT lymphoma was considered. We identified a subset of cases primary to the urinary bladder, presenting with prominent plasma cell infiltrates and symptoms mimicking bladder pain syndrome/interstitial cystitis. These proliferations were designated for this study as "monotypic plasma cell proliferation of uncertain clinical significance" (MPCP-US), as the features were insufficient for diagnosis of MALT lymphoma. We identified 33 patients, consisting of 22 cases of MPCP-US (6 of which were associated with amyloid deposition) and 11 cases of MALT lymphoma. MPCP-US was more prevalent in men (73%), a mass lesion was not identified at cystoscopy, and only 1 case had an accompanying urinary tract infection (4.5%). Histologically, MPCP-US presented as monotypic plasma cells arranged in a superficial band-like distribution in the lamina propria, predominantly kappa restricted (68%) and IgA+ or IgM+ (64% and 23%, respectively) and without a histologic mass of atypical B cells or plasma cells, not diagnostic for established MALT lymphoma or plasmacytoma. Secondary involvement of the bladder by other lymphoproliferative disorders was excluded and there was no evidence of progressive disease. MALT lymphomas are presented for comparison and our analysis demonstrated that MPCP-US represent a different clinicopathologic entity compared with classic MALT lymphoma. We present the first series of cases of MPCP-US. The recognition of this entity is fundamental to the development of management protocols to relieve intractable symptoms mimicking bladder pain syndrome/interstitial cystitis in these patients.

Endobronchial Extranodal Marginal Zone B-Cell Lymphoma with Plasmacytic Differentiation

Endobronchial tumors (ET) are unusual and mostly malignant, presenting with non-specific symptoms that often delay appropriate diagnosis and treatment. Lymphomas in the airway represent less than 1% of pulmonary malignancies and require multidisciplinary approach for their management. We present a case of a 48-year-old male former smoker with a one-year history of recurrent respiratory infections and new-onset shortness of breath. Diagnostic tests included a chest computed tomography (CT) reporting the presence of an endobronchial mass and neck and cervical lymph node biopsies with inconclusive results. Bronchoscopy was successfully performed for tumor resection, improving the patient’s respiratory symptoms. Histological analysis described an extranodal marginal zone B-cell lymphoma (ENMZL) with plasmacytic differentiation; a subtype of non-Hodgkin’s lymphoma (NHL) in mucosa-associated lymphoid tissue (MALT), rarely found as an endobronchial growth. ET should be considered in the setting of persistent and worsening respiratory symptoms. ENMZL with plasmacytic differentiation is rarely found as an ET and diagnosis requires bronchoscopic intervention and extensive immunohistochemical analysis.

Histologic transformation of t(11;18)-positive MALT lymphoma presented with aberrant T-cell marker expression

Mucosa-associated lymphoid tissue (MALT) lymphoma with t(11;18)(q21;q21), resulting in an API2-MALT1 fusion transcript, is reported to rarely transform into aggressive lymphoma. Here, we report the clinical course of a patient who experienced histologic transformation after 20 years' disease history of t(11;18)-positive MALT lymphoma. The patient suddenly developed a large intrapelvic mass and ascites with a rapid increase in lactate dehydrogenase. Cytology of the ascites detected large abnormal cells, and flow cytometric analysis revealed that the cells were positive for cytoplasmic CD3, CD4, and CD38, and partially positive for CD7, but negative for CD19 and CD20. Antigen receptor gene rearrangement analysis and in situ hybridization of the immunoglobulin light chains confirmed that the tumor cells were of B-cell lineage. Chromosomal analysis showed complex karyotypes with intraclonal variation, and in addition to t(11;18), t(8;14) and heterozygous loss of the TP53 were demonstrated. Although histological and phenotypic features were significantly altered from the original MALT lymphoma, the presence of t(11;18) led us to the diagnosis of histologic transformation of MALT lymphoma. Although transformation of t(11;18)-positive MALT lymphoma into aggressive lymphoma is extremely rare, it may occur, probably with additional genetic abnormalities such as cMYC rearrangement and/or the loss of TP53.

Contemporary management of nodal and primary splenic marginal zone lymphoma

Introduction: Marginal zone lymphoma (MZL) accounts for approximately 10% of all cases of non-Hodgkin lymphoma and includes 3 clinically distinct subtypes: extranodal (MALT), splenic (SMZL), and nodal (NMZL). Though commonly grouped in trials of iNHL the clinical behavior, molecular features, and response to therapy of MZL is distinct from other iNHL subtypes and varies among MZL subtypes.Areas covered: This review focuses on the contemporary management of NMZL and SMZL. Treatment with monoclonal antibodies, chemoimmunotherapy, BTK inhibitors, PI3K/mTOR inhibitors, Bcl2 inhibitors, lenalidomide, and CAR-T cell therapy will be covered.Expert opinion: In the era of targeted medicine, the need to develop MZL specific clinicogenetic models with prognostic and predictive value in both the frontline and relapsed/refractory setting is becoming increasingly apparent. Due to the relative rarity of each MZL subtype, the use of novel trial design with correlative studies is imperative to advance the field.

Clonal relationship of marginal zone lymphoma and diffuse large B-cell lymphoma in Sjogren's syndrome patients: case series study and review of the literature

The occurrence of diffuse large B-cell lymphoma (DLBCL) in the course of Sjogren's syndrome (SS) is considered to be equally related either to the development of DLBCL de novo or to the transformation from marginal zone lymphoma (MZL). However, the question of possible clonal relationship between MZL and DLBCL in the group of SS patients remains open. Here we present the data concerning 194 patients with lymphoma complicated SS followed up at Nasonova Research Institute of Rheumatology during the last 22 years. Molecular analysis of tumor cells was performed for 6 SS patients who had developed both MZL and DLBCL. To assess clonal relationship between each of the tumor pairs immunoglobulin heavy chain (IGH) gene rearrangements were identified according BIOMED-2 protocol by means of multiplex polymerase chain reaction followed by GeneScan fragment analysis. Despite different localization MZL and DLBCL were clonally related in five tumor pairs. The median time to transformation was 11 months (range 0-78 months). MZL and DLBCL were clonally related in most cases from our cohort of SS patients. No statistically significant difference in survival between patients with DLBCL transformed from MZL and patients with de novo DLBCL was found in the cohort of SS patients investigated.

The utility of prognostic indices, early events, and histological subtypes on predicting outcomes in non-follicular indolent B-cell lymphomas

Indolent B-cell lymphomas other than follicular lymphoma account for up to 10% of all B-cell neoplasms. While they typically follow a slowly progressive course, some patients experience rapid progression and early mortality. Prognostic scoring systems have not been adopted, hindering the ability of clinicians or researchers to predict outcomes, or risk-stratify patients during clinical trials. To address this, we evaluated the utility of existing prognostic indices and novel, early disease-related outcomes, to predict subsequent long term survival. Baseline characteristics and outcomes data were generated from a longitudinal cohort study that prospectively enrolled 632 patients newly diagnosed with marginal zone lymphoma, lymphoplasmacytic lymphomas, or B-cell lymphomas not otherwise specified, beginning in 2002. The International Prognostic Index (IPI), Follicular Lymphoma International Prognostic Index (FLIPI), and MALT International prognostic index (MALT-IPI) demonstrated c-statistics that ranged from 0.593-0.612 for event-free survival (EFS), and 0.683-0.714 for overall survival (OS). Patients who attained event-free survival at 12 months (EFS12) experienced similar mortality to the US general population (standardized mortality ratio [SMR] 1.19; 95% CI 0.95-1.46). Patients who did not attain EFS12 had subsequent worse morality (SMR 3.14 (95% CI 2.05-4.59). The MALT-IPI demonstrated utility in predicting subsequent long-term outcomes among patients with non-follicular indolent B-cell lymphomas. This index should be used by clinicians giving guidance to patients at the time of initial diagnosis, and risk stratification during clinical studies. The divergent long-term outcomes experienced by patients who do or do not attain EFS12 suggest there exists a subset of patients who harbor high-risk disease. Future research efforts should focus on methods to identify these patients at the time of diagnosis, in order to enable risk-tailored therapy.

Short survival and frequent transformation in extranodal marginal zone lymphoma with multiple mucosal sites presentation

Between 11 and 37% of extranodal marginal zone lymphoma (EMZL) patients present with disease involvement in multiple mucosal sites (MMS). We analyzed 405 EMZL patients seen between 1995 and 2017: 265 (65.4%) patients presented with stage I disease, 49 of 309 (15.8%) patients with bone marrow involvement, and 35 of 328 (10.7%) patients with monoclonal gammopathy (MG). Forty-three (10.6%) patients had MMS presentation, which was more frequently seen in patients aged >60 years (55.8%). Five (17.9%) of 28 MMS patients had MG. MMS patients commonly exhibited the International Prognostic Index (IPI) >2 (79.1%), Follicular Lymphoma International Prognostic Index (FLIPI) >2 (39.5%), and Mucosa-Associated Lymphoid Tissue Lymphoma International Prognostic Index (MALT-IPI) 2-3 (60.5%). Both MMS presentation and MG were associated with shorter survival univariately. In multivariable Cox regression models, shorter progression-free survival (PFS) and overall survival (OS) were observed in patients with MMS (hazard ratio [HR] = 3.08 and 2.92, respectively), age ≥60 years (HR = 1.52 and 2.45, respectively), and in patients who failed to attain a complete remission following initial therapy (HR = 3.27 and 2.13, respectively). Elevated lactate dehydrogenase was associated with shorter PFS (HR = 1.92), while anemia (HR = 2.46) was associated with shortened OS. MALT-IPI ≥2 (HR = 2.47 and 4.75), FLIPI >2 (HR = 1.65 and 2.09), and IPI >2 (HR = 2.09 and 1.73) were associated with shorter PFS and OS, respectively. Higher grade transformation (HGT) occurred in 11 (25.6%) MMS patients with a 5-year cumulative incidence of 13.2% (95% CI 4.7-26.1%). EMZL patients with MMS presentation represent a novel clinical subset associated with shorter PFS, OS, and higher incidence of HGT that needs novel therapeutic approaches.

IRTA1 and MNDA Expression in Marginal Zone Lymphoma: Utility in Differential Diagnosis and Implications for Classification

Objectives

To evaluate the clinical utility of immune receptor translocation-associated protein 1 (IRTA1) and myeloid nuclear differentiation antigen (MNDA) expression in the diagnosis and classification of marginal zone lymphomas (MZLs).

Methods

IRTA1 was examined using a novel RNA in situ hybridization assay and MNDA expression determined by immunohistochemistry in 127 small B-cell neoplasms, including 80 cases of MZL.

Results

IRTA1 expression was detected in 31 (42%) of 74 MZLs vs one (2%) of 43 other small B-cell neoplasms (P < .001). MNDA staining was positive in 51 (64%) of 79 MZLs vs 21 (45%) of 46 non-MZLs (P = .06). MNDA expression was particularly uncommon in follicular lymphoma (3/14, 21%; P = .003 vs MZL). There was no association between MNDA and IRTA1 expression and the presence of monocytoid cytology. IRTA1 expression was less frequent in cases with a diffuse growth pattern.

Conclusions

IRTA1 and MNDA are useful markers in the differential diagnosis of MZLs.

18F-FDG PET/CT in splenic marginal zone lymphoma

PURPOSE

The detection rate and the metabolic behavior of 18F-FDG-PET/CT in splenic marginal zone lymphoma (SMZL) are not yet clear. Our aim was to investigate the metabolic behavior of SMZL and whether the tumor stage (acc. Ann Arbor) epidemiological (age, gender), histological (Ki-67 index, plasmacytic differentiation), and morphological (splenic diameter maximum) features might be related to 18F-FDG PET/CT results.

METHODS

Fifty-one patients (34 male, 17 female; average age 70 years) with histologically confirmed SMZL who underwent a 18F-FDG PET/CT for initial staging were included: PET/CT images were analyzed visually and semi-quantitatively (SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio). Splenic uptake was divided as diffuse or focal.

RESULTS

Thirty-nine patients (76%) had FDG-avid SMZL (7 with focal splenic lesions and 32 with diffuse splenic uptake), while the remaining 12 had no increased splenic uptake. Among patients with FDG-avid lesions, average SUVmax was 4.3, lesion-to-liver SUVmax ratio 2.3, and lesion-to-blood pool SUVmax ratio 3. 18F-FDG avidity was significantly associated with Ki-67 index and not correlated with other features. Semiquantitative PET/CT parameters (SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio) did not correlate significantly with any variable. Progression-free survival time was not influenced by FDG avidity of SMZL.

CONCLUSIONS

18F-FDG avidity was noted in 76% of SMZL with diffuse splenic uptake as main pattern of presentation and is correlated with Ki-67 score only.

Gastric MALT Lymphoma with Increased Plasma Cell Differentiation Showing Unique Endoscopic Features

A 62-year-old woman was diagnosed with extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) with increased plasma cell differentiation of the stomach. Esophagogastroduodenoscopy showed slightly elevated, whitish lesions in the gastric body. Magnifying endoscopic observation revealed that the gastric surface epithelium was swollen, but the structure was not destroyed or diminished. Elongated, tortuous vasculature was observed on the surface of the whitish lesions. The patient underwent eradication treatment for Helicobacter pylori, which resulted in complete remission. Although the appearance of abnormal vessels and the destruction of gastric epithelial structure are the typical features of gastric MALT lymphoma during magnifying endoscopy, the present case showed different features, which were rather similar to those observed in a previously reported case of gastric plasmacytoma. The current case indicates that magnifying endoscopic features are not uniform among gastric MALT lymphomas.

Marginal zone lymphoma of palatine tonsil with prominent plasmacytic differentiation: A CARE-compliant article and review of literature

RATIONALE

The palatine tonsil is an important component of Waldeyer's ring and a site commonly involved by lymphoma. Interestingly, although it is a site of mucosa-associated lymphoid tissue (MALT), primary MALT lymphoma of the palatine tonsil is rare, especially with prominent plasmacytic differentiation.

PATIENT CONCERNS

A 59-year-old woman presented to the hospital with a 1-month history of odynophagia. The patient had no fever or pruritus during this period and she declared no family history of hematolymphoid malignancy.

DIAGNOSIS

Histopathological examination demonstrated effacement of tonsil architecture; normal follicles were replaced by plasmacytoid tumor cells and small lymphocytes. The tumor cells expanded the marginal zone and infiltrated interfollicular regions, as well as scattered residual follicles. Immunostaining showed tumor cells positive for cluster of differentiation (CD)20, CD79a, paired box-5, Mum 1, and B cell lymphoma (Bcl)-2, and negative for CD5, CD 23, cyclin D1, Bcl-6, and CD10. Staining for κ and λ showed prominent light chain restriction. The tumor was classified as tonsil MALT lymphoma with prominent plasmacytic differentiation.

INTERVENTIONS

After the patient was diagnosed with MALT lymphoma with prominent plasmacytic differentiation, she underwent complete surgical resection and radiotherapy.

OUTCOMES

There was no recurrence evident at 6-months follow-up.

LESSONS

Primary tonsil MALT lymphoma with prominent plasmacytic differentiation is very rare and difficult to distinguish from other B-cell lymphomas with plasmacytoid morphology, such as follicular lymphoma, lymphoplasmacytic lymphoma, and chronic lymphocytic leukemia/small lymphocytic lymphoma. Accurate diagnosis of this entity is important in guiding therapy so as to avoid overtreatment.

Diagnostic Algorithm of Common Mature B-Cell Lymphomas by Immunohistochemistry

CONTEXT

- Different types of mature B-cell lymphomas, including plasma cell neoplasms, exhibit distinct immunohistochemical profiles, which enable them to be correctly diagnosed. However, except for rare examples of lymphoma-specific immunohistochemistry, such as cyclin D1 in mantle cell lymphoma and annexin A1 in hairy cell leukemia, immunohistochemical profiles of mature B-cell lymphomas overlap and lack specificity.

OBJECTIVES

- To systemically review immunohistochemical features associated with commonly encountered mature B-cell lymphomas based on the presence or absence of CD5 and CD10; to review the immunophenotypic profile of plasma cells derived from plasma cell myelomas and B-cell lymphomas; and to review a group of rare, aggressive B-cell lymphomas with antigen expression features of plasma cells.

DATA SOURCES

- Published and PubMed-indexed English literature was reviewed.

CONCLUSIONS

- Although the presence or absence of CD5 and CD10 expression should be included in the initial immunohistochemistry screening panel for mature B-cell lymphomas, appropriate and judicial use of other B-cell antigens is necessary to ensure correct diagnoses. Furthermore, although the status of CD5 and CD10 expression is associated with certain prototypes of B-cell lymphomas, their expression is not specific. Plasma cells from plasma cell neoplasias and B-cell lymphomas exhibit overlapping but relatively distinct immunophenotypes; thus, a panel of immunohistochemical markers (CD19, CD45, CD56, and CD117) can be employed for their proper identification. Lastly, CD138 staining results are almost always positive in a group of aggressive B-cell lymphomas with plasmablastic features, including plasmablastic plasma cell myeloma, plasmablastic lymphoma, and ALK-1⁺ large B-cell lymphoma.

B-cell Non-Hodgkin Lymphomas with Plasmacytic Differentiation

B-cell non-Hodgkin lymphomas with plasmacytic differentiation are a diverse group of entities with extremely variable morphologic features. Diagnostic challenges can arise in differentiating lymphoplasmacytic lymphoma from marginal zone lymphoma and other low-grade B-cell lymphomas. In addition, plasmablastic lymphomas can be difficult to distinguish from diffuse large B-cell lymphoma or other high-grade lymphomas. Judicious use of immunohistochemical studies and molecular testing can assist in appropriate classification.

The Comparative Diagnostic Features of Canine and Human Lymphoma

The non-Hodgkin lymphomas (NHLs) are a heterogeneous family of lymphoid malignancies that are among the most common neoplasms of both dogs and humans. Owing to shared molecular, signaling, incidence, and pathologic features, there is a strong framework supporting the utilization of canine lymphoma as a comparative, large animal model of human NHL. In alignment with the biologic similarities, the current approach towards the diagnosis and classification of canine lymphoma is based upon the human World Health Organization guidelines. While this approach has contributed to an increasing appreciation of the potential biological scope of canine lymphoma, it has also become apparent that the most appropriate diagnostic philosophy must be multimodal, namely by requiring knowledge of microscopic, immunophenotypic, and clinical features before establishing a final disease diagnosis. This review seeks to illustrate the comparative similarities and differences in the diagnosis of canine lymphoma through the presentation of the microscopic and immunophenotypic features of its most common forms.

Optimizing therapy for nodal marginal zone lymphoma

Nodal marginal zone lymphoma (NMZL) is a rare form of indolent small B-cell lymphoma which has only been clearly identified in the last 2 decades and which to date remains incurable. Progress in therapeutic management has been slow, largely due to the very small number of patients treated and the heterogeneity of treatments administered; thus, standard-of-care treatment is currently nonspecific for this lymphoma entity. In this review, treatments routinely used to manage adult NMZL patients are presented, principally based on immunochemotherapy (when treatment is needed). Biological research behind the key axes of agents currently under development is described; development of novel agents is heavily based on data from gene profiling and genome-wide sequencing research, uncovering a number of critical deregulated pathways specific to NMZL tumors. These include B-cell receptor, JAK/STAT, NF-κB, NOTCH, and Toll-like receptor signaling pathways, as well as intracellular processes such as the cell cycle, chromatin remodeling, and transcriptional regulation in terms of epigenetic modifiers, histones, or transcriptional co-repressors, along with immune escape via T-cell-mediated tumor surveillance. These pathways are examined in detail and a projection of how the field may evolve in the near future for an efficient personalized treatment approach for NMZL patients is presented.

Plasma cell and terminal B-cell differentiation in mantle cell lymphoma mainly occur in the SOX11-negative subtype

Mantle cell lymphoma is a mature lymphoid neoplasm characterized by the t(11;14)(q13;q32) and cyclin D1 overexpression. SOX11 is a transcription factor commonly overexpressed in these tumors but absent in most other mature B-cell lymphomas whose function is not well understood. Experimental studies have shown that silencing of SOX11 in mantle cell lymphoma cells promotes the shift from a mature B cell into an early plasmacytic differentiation phenotype, suggesting that SOX11 may contribute to tumor development by blocking the B-cell differentiation program. The relationship between SOX11 expression and terminal B-cell differentiation in primary mantle cell lymphoma and its relationship to the plasmacytic differentiation observed in occasional cases is not known. In this study we have investigated the terminal B-cell differentiation phenotype in 60 mantle cell lymphomas, 41 SOX11-positive and 19 SOX11-negative. Monotypic plasma cells and lymphoid cells with plasmacytic differentiation expressing cyclin D1 were observed in 7 (37%) SOX11-negative but in none of 41 SOX11-positive mantle cell lymphomas (P<0.001). Intense cytoplasmic expression of a restricted immunoglobulin light chain was significantly more frequent in SOX11-negative than -positive tumors (58 vs 13%) (P=0.001). Similarly, BLIMP1 and XBP1 expression was also significantly more frequent in SOX11-negative than in -positive cases (83 vs 34% and 75 vs 11%, respectively) (P=0.001). However, no differences in the expression of IRF4/MUM1 were observed among these subtypes of mantle cell lymphoma. In conclusion, these results indicate that SOX11-negative mantle cell lymphoma may be a particular subtype of this tumor characterized by more frequent morphological and immunophenotypic terminal B-cell differentiation features that may be facilitated by the absence of SOX11 transcription factor.

Masses in the membranes

A 24-year-old woman with systemic lupus erythematosus presented with a 1-year history of painless vision loss in the right eye. Examination was notable for a bitemporal hemianopia. Brain imaging revealed multiple contrast enhancing dural masses, including one along the planum sphenoidale. She underwent excisional biopsy for a presumed diagnosis of multiple meningiomas. Five years later, she developed worsening vision in the left eye, hypesthesia in the V1 distribution, and oculomotor nerve palsy. Repeat imaging showed an enhancing mass in the cavernous sinus and orbital apex. Biopsy demonstrated a lymphoplasmacyte rich infiltrate in dense extracellular material. She was diagnosed with lupus-induced hypertrophic pachymeningitis and started on immunosuppressive therapy. On further worsening of symptoms, her initial biopsy was reexamined and revealed a kappa light chain restricted B-cell and plasmacyte population. This led to the final diagnosis of central nervous system extranodal marginal zone lymphoma.

MYD88 (L265P) somatic mutation in marginal zone B-cell lymphoma

MYD88 L265P is a somatic mutation that has been identified in about 90% of Waldenström macroglobulinemia/lymphoplasmacytic lymphomas (LPLs). It has also been detected in a subset of marginal zone lymphoma (MZL) cases, but the frequency and clinical and histologic features of these mutated MZL cases has only been partially characterized. We have developed a customized TaqMan allele-specific polymerase chain reaction for sensitive detection of this mutation in paraffin-embedded tissue. We analyzed samples from 19 patients with LPL, 88 patients with splenic marginal zone lymphoma (SMZL), 8 patients with nodal marginal zone lymphoma (NMZL), 21 patients with extranodal mucosa-associated lymphoid tissue (MALT), and 2 patients with B-cell lymphoma not otherwise specified. By integrating mutational, histologic, and clinical data, 5 cases were reclassified as LPL. After reclassification, MYD88 L265P was detected in 13/86 (15%) SMZL and in 19/24 LPL (79%) cases. The mutation was absent from NMZL and MALT cases. A strong correlation was found between the presence of an IgM monoclonal paraproteinemia and the MYD88 L265P mutation (P<0.0001). SMZL cases positive for MYD88 L265P were also associated with monoclonal IgM paraproteinemia (4/13 cases; P<0.0283), although with less serum paraproteinemia. They also had a higher frequency of plasmacytic differentiation (9/13) but with no correlation between the presence of mutation and of light chain-restricted plasma cells in tissue. Demonstration of the MYD88 L265 mutation is a valuable tool for the diagnosis of LPL, although some SMZL cases carrying the mutation do not fulfill the diagnostic criteria for LPL.

MYD88 L265P mutation analysis helps define nodal lymphoplasmacytic lymphoma

The diagnosis of lymphoplasmacytic lymphoma is often challenging, especially in extramedullary tissues where the differential diagnosis includes nodal marginal zone lymphoma, splenic marginal zone lymphoma, or other small B-cell neoplasms with plasmacytic differentiation. The MYD88 L265P mutation has been recently identified in >90% of bone-marrow-based lymphoplasmacytic lymphoma, but the incidence of this abnormality and corresponding morphologic correlates in nodal lymphoplasmacytic lymphoma have not been established. We analyzed 87 cases of extramedullary lymphoplasmacytic lymphoma, splenic marginal zone lymphoma, unclassifiable splenic B-cell lymphomas, nodal marginal zone lymphoma with plasmacytic differentiation, and chronic lymphocytic leukemia/small lymphocytic lymphoma with plasmacytic differentiation for MYD88 L265P. Eighteen cases (21%) were positive, including 9/9 (100%) lymphoplasmacytic lymphomas with classic histologic features, 5/12 (42%) cases that met 2008 WHO criteria for lymphoplasmacytic lymphoma but with atypical morphologic features, 3/15 (20%) cases initially considered nodal marginal zone lymphoma with plasmacytic differentiation, and 1/6 (17%) unclassifiable splenic B-cell lymphomas. The presence of MYD88 L265P was associated with IgM paraprotein (P<0.001) and a trend for bone marrow involvement (P=0.09). Each of 44 splenectomy-defined splenic marginal zone lymphomas (19 with plasmacytic differentiation) and the chronic lymphocytic leukemia/small lymphocytic lymphoma with plasmacytic differentiation were negative for the mutation. Morphologic re-review with knowledge of MYD88 mutation status and all available clinical features suggested all MYD88 mutated cases were consistent with lymphoplasmacytic lymphoma (either classic or variant histology), except for one case which remained most consistent with nodal marginal zone lymphoma with plasmacytic differentiation. These results demonstrate the importance of MYD88 mutational analysis in better defining lymphoplasmacytic lymphoma as a relatively monomorphic small B-cell lymphoma with plasmacytic differentiation that may show total nodal architectural effacement and follicular colonization. Cases previously considered lymphoplasmacytic lymphoma that are more polymorphous and are often associated with histiocytes should no longer be included in the lymphoplasmacytic lymphoma category. Clinicopathologic review suggests that although MYD88 mutated non-lymphoplasmacytic lymphoma small B-cell neoplasms exist, they are very uncommon.

Concomitant Presence of Two Distinct Clones of Chronic Lymphocytic Leukemia and Plasma Cell Myeloma in a Patient

A 74 years old male patient, presented with history of generalized weakness, fatigue, loss of appetite and breathlessness on exertion for past one and a half months. On examination, he was found to have significant pallor and generalized lymphadenopathy (cervical, axillary and inguinal). The skeletal survey showed punched out lytic lesions in skull and pelvic bones. The peripheral smear examination showed lymphocytosis with absolute lymphocyte count of 25,000/μL. The bone marrow aspirates revealed a hypercellular marrow with 74 % lymphocytes & 14 % plasma cells, suggestive of chronic lymphoplasmacytic disorder. The bone marrow biopsy had two morphologically distinct populations of lymphocytes & plasma cells. The immunohistochemical markers on bone marrow biopsy showed hat plasma cells were positive for CD138 with kappa light chain restriction. Flow cytometry showed B cell population with CD19/CD5 co expression, CD5/CD23 coexpression, were positive for CD22, CD20 and negative for FMC-7 and lambda light chain. In addition, plasma cells were also identified as CD45 negative cells and showed CD38/CD138 co-expression with variable CD19 and CD56 positivity. Serum protein electrophoresis revealed M band, serum immunofixation electrophoresis corresponded to IgA -Kappa. The final diagnosis of chronic lymphocytic leukemia with concomittant presence of plasma cell myeloma was concluded. This case imparts an important message to look for presence of coexisting entities in a single specimen and highlights the benefits of testing both plasma cell and B-cell compartments when the clinical features are not entirely consistent Flow cytometry together with protein electrophoresis can help to clinch difficult and rare dual diagnosis. These cases are rare and pose therapeutic challenge.

Extranodal Marginal Zone Lymphoma of the Lung: Evolution from an Underlying Reactive Lymphoproliferative Disorder

Extranodal Marginal Zone Lymphoma (ENMZL) of Mucosa-Associated Lymphoid Tissue (MALT) is a problematic and sometimes controversial diagnosis. While commonly seen in the stomach in the setting of chronic Helicobacter pylori infection, other extranodal sites, such as the lung, may also present with disease. ENMZL is clinically and morphologically heterogeneous; however, regardless of presentation, the etiology lies in the accumulation of lymphoid tissue in non-traditional sites. This phenomenon is typically secondary to an underlying inflammatory stimulus such as chronic infection or autoimmune states. The current case report details the clinical history of a patient with Sjögren syndrome over a four year period who eventually developed ENMZL. The patient initially presented with an atypical, but polyclonal, lymphoproliferative process diagnosed as lymphocytic interstitial pneumonia. Over time, the patient showed evolution to a monoclonal process with associated radiologic progression of disease. This evolution manifested as a dense lymphoid infiltrate with prominent plasmacytic differentiation and the development of a lung mass radiologically. This case contributes to the growing body of knowledge that suggests ENMZL lies along a biological spectrum of lymphoproliferative disorders whereby a benign, reactive process may eventually undergo malignant transformation. This evolution likely represents the acquisition of genetic abnormalities that allow autonomous proliferation in the absence of the initial immune stimulus. In practice, determining when this event occurs and, thus, distinguishing between reactive and neoplastic disorders within this spectrum may be difficult as no single clinicopathologic feature may be present to establish the diagnosis. This case further illustrates the importance of correlating the clinical, radiologic and pathologic data to evaluate patients with atypical pulmonary lymphoproliferative disorders and to allow the optimal management of their disease.

Recognizing nodal marginal zone lymphoma: recent advances and pitfalls. A systematic review

The diagnosis of nodal marginal zone lymphoma is one of the remaining problem areas in hematopathology. Because no established positive markers exist for this lymphoma, it is frequently a diagnosis of exclusion, making distinction from other low-grade B-cell lymphomas difficult or even impossible. This systematic review summarizes and discusses the current knowledge on nodal marginal zone lymphoma, including clinical features, epidemiology and etiology, histology, and cytogenetic and molecular features. In particular, recent advances in diagnostics and pathogenesis are discussed. New immunohistochemical markers have become available that could be used as positive markers for nodal marginal zone lymphoma. These markers could be used to ensure more homogeneous study groups in future research. Also, recent gene expression studies and studies describing specific gene mutations have provided clues to the pathogenesis of nodal marginal zone lymphoma, suggesting deregulation of the nuclear factor kappa B pathway. Nevertheless, nodal marginal zone lymphoma remains an enigmatic entity, requiring further study to define its pathogenesis to allow an accurate diagnosis and tailored treatment. However, recent data indicate that it is not related to splenic or extranodal lymphoma, and that it is also not related to lymphoplasmacytic lymphoma. Thus, even though the diagnosis is not always easy, it is clearly a separate entity.

An unusual case of Waldenstrom's macroglobulinemia presented with nasopharyngeal involvement

We report a rare case of a 68-year-old male who presented with fever, weight loss, nasal blockage, and epistaxis. Examination revealed cervical and axillary lymphadenopathy with no evidence of organomegaly. On evaluation, bone marrow aspiration showed lymphoplasmacytic infiltration. The computed tomography of the neck showed nasopharyngeal mass and the biopsy of this mass and cervical lymph node showed lymphoplasmacytic lymphoma (LPL) with high serum IgM level. Hence, a diagnosis of Waldenstrom’s macroglobulinemia (WM) was made. The patient received six cycles of chemotherapy with a combination of cyclophosphamide, vincristine, and prednisolone (COP regimen). Currently, the patient is under follow-up and in complete remission (CR), one year after completion of therapy. Nasopharyngeal involvement is extremely rare in WM, and hence we report this case.

Immunoarchitectural patterns of germinal center antigens including LMO2 assist in the differential diagnosis of marginal zone lymphoma vs follicular lymphoma

OBJECTIVES

To examine the immunoarchitectural patterns of the germinal center (GC)-associated markers CD10, BCL6, and LMO2 and their utility in the differential diagnosis of marginal zone lymphoma (MZL) vs follicular lymphoma (FL).

METHODS

Forty-two cases of MZL involving lymph nodes and 88 cases of FL were examined.

RESULTS

Interfollicular staining for GC markers was uncommon in MZL but common in FL, including BCL2-positive and BCL2-negative cases. Two atypical patterns of intrafollicular GC staining were identified that were more common in MZL than in FL.

CONCLUSIONS

Staining for LMO2 in addition to CD10 and BCL6 facilitates the detection of a GC phenotype in FL. Lymph nodes involved by MZL frequently show characteristic alterations of GC immunoarchitecture. Recognizing these altered patterns assists in the distinction between MZL and FL.

Diagnostic and clinical considerations in concomitant bone marrow involvement by plasma cell myeloma and chronic lymphocytic leukemia/monoclonal B-cell lymphocytosis: a series of 15 cases and review of literature

CONTEXT

Plasma cell myeloma and chronic lymphocytic leukemia are both common hematologic malignancies, sharing many epidemiologic features. Concomitant detection of the 2 conditions poses special diagnostic challenges for the pathologist.

OBJECTIVE

To describe the pathologic findings in cases of concomitant bone marrow involvement by myeloma and CD5(+) monoclonal B cells and to outline the differential diagnostic possibilities, suggest a workup for correct diagnosis, and examine clinical outcome.

DESIGN

Fifteen cases that met the diagnostic criteria were identified from pathology databases at 4 participating institutions. Morphologic findings were reviewed, additional immunohistochemical stains performed, and flow cytometric, cytogenetic, and relevant laboratory and clinical information was summarized. Previously published cases were searched from electronic databases and cross-references.

RESULTS

Most patients (13 of 15) were older males. Often (11 of 15) they presented clinically with myeloma, yet had both monotypic plasma cells and B cells in the diagnostic marrow. In 4 patients, myeloma developed 24 months or later after chronic lymphocytic leukemia. In 7 patients, myeloma and CD5(+) B cells showed identical immunoglobulin light-chain restriction. Primary differential diagnoses include lymphoplasmacytic lymphoma, marginal zone lymphoma, and chronic lymphocytic leukemia with plasmacytoid differentiation. CD56 and/or cyclin D1 expression by plasma cells was helpful for correct diagnosis. Most patients in our cohort and published reports were treated for plasma cell myeloma.

CONCLUSIONS

Concomitant detection of myeloma and chronic lymphocytic leukemia in the bone marrow is a rare event, which must be carefully differentiated from lymphomas with lymphoplasmacytic differentiation for correct treatment.

Lymphoplasmacytic lymphoma and Waldenström macroglobulinemia

Lymphoplasmacytic lymphoma (LPL) is a low-grade, B-cell neoplasm composed of small lymphocytes, plasmacytoid lymphocytes, and plasma cells that typically involve the bone marrow, and it is associated with an immunoglobulin M (IgM) gammopathy. The definition of Waldenström macroglobulinemia (WM) and its relationship to LPL has been confusing in the past. In addition, the diagnosis of LPL itself can be challenging because LPL lacks disease-specific morphologic, immunophenotypic, and genetic features to differentiate it from other mature B-cell neoplasms. Accurate diagnosis of LPL/WM rests on recognition of the differential diagnostic features between LPL and other diagnostic possibilities and the use of the recently refined definition of WM and its relationship with LPL: The presence of an IgM monoclonal gammopathy of any level in the setting of bone marrow involvement by LPL. This review summarizes the clinical, laboratory, and histologic features of LPL/WM, with particular emphasis on unique aspects of LPL/WM that may aid in accurate diagnosis.

[B-cell neoplasms with plasmacellular and plasmablastic differentiation]

Plasma cell malignancies are tumors of terminally differentiated B-cells in which the neoplastic plasma cells are the dominant and proliferating tumor cell component. Plasma cell myeloma (PCM) is one of the most common hematological neoplasms and typically does not cause diagnostic problems. A morphologically and immunophenotypically detectable plasmacellular orplasmablastic differentiation is, however, commonly observed in a wide range of mature B-cell lymphomas. A confident separation of the distinct entities requires the integration of clinical and morphological findings as well as an adequate phenotyping of both the plasma cell and the B-cell component if present. Detection of lymphotropic viruses, specific translocations and novel molecular markers, such as the MYD88 L265P mutation occurring in the vast majority of lymphoplasmacytic lymphomas complement our diagnostic repertoire. In this review we describe the most commonly observed diagnostic problems in separating small B-cell lymphomas from PCM and high-grade B-cell non-Hodgkin lymphoma (B-NHL) with plasmablastic differentiation from extramedullary spread of aggressive PCM and provide helpful criteria for routine diagnostics.