Benign lymphoid aggregates in the bone marrow: distribution patterns of B and T lymphocytes

Multimodal spatial proteomic profiling in acute myeloid leukemia

Acute myeloid leukemia (AML) resides in an immune-rich microenvironment, yet, immune-based therapies have faltered in eliciting durable responses. Bridging this paradox requires a comprehensive understanding of leukemic interactions within the bone marrow microenvironment. We optimized a high-throughput tissue-microarray-based pipeline for high-plex spatial immunofluorescence and mass cytometry imaging on a single slide, capturing immune, tumor, and structural components. Using unbiased clustering on the spatial K function, we unveiled the presence of tertiary lymphoid-like aggregates in bone marrow, which we validated using spatial transcriptomics and an independent proteomics approach. We then found validated TLS signatures predictive of outcomes in AML using an integrated public 480-patient transcriptomic dataset. By harnessing high-plex spatial proteomics, we open the possibility of discovering novel structures and interactions that underpin leukemic immune response. Further, our study's methodologies and resources can be adapted for other bone marrow diseases where decalcification and autofluorescence present challenges.

In vivo tracking of ex-vivo-generated 89Zr-oxine-labeled plasma cells by PET in a non-human primate model

B cells are an attractive platform for engineering to produce protein-based biologics absent in genetic disorders, and potentially for the treatment of metabolic diseases and cancer. As part of pre-clinical development of B cell medicines, we demonstrate a method to collect, ex vivo expand, differentiate, radioactively label, and track adoptively transferred non-human primate (NHP) B cells. These cells underwent 10- to 15-fold expansion, initiated IgG class switching, and differentiated into antibody-secreting cells. Zirconium-89-oxine-labeled cells were infused into autologous donors without any preconditioning and tracked by PET/CT imaging. Within 24 h of infusion, 20% of the initial dose homed to the bone marrow and spleen and distributed stably and equally between the two. Interestingly, approximately half of the dose homed to the liver. Image analysis of the bone marrow demonstrated inhomogeneous distribution of the cells. The subjects experienced no clinically significant side effects or laboratory abnormalities. A second infusion of B cells into one of the subjects resulted in an almost identical distribution of cells, suggesting possibly a non-limiting engraftment niche and feasibility of repeated infusions. This work supports the NHP as a valuable model to assess the potential of B cell medicines as potential treatment for human diseases.

AL amyloidosis manifesting as a vertebral amyloidoma secondary to an unrecognized plasmacytoma expressing cyclin D1 case report

INTRODUCTION

Immunoglobin-related (AL) amyloidosis is the production of amyloidogenic immunoglobulin light chains from clonal plasma cells or, rarely, B-cell lymphomas with plasmacytic differentiation. Amyloid deposition causes progressive end organ destruction with profound morbidity.

PRESENTATION OF CASE

We present a rare case of a lambda light chain AL amyloidoma localized to a thoracic vertebra of an 87-year-old woman who had a remote history of an unspecified non-Hodgkin B-cell lymphoma (NHL). Our patient presented with upper extremity neuropathy and was found by MRI to have a malignant-appearing lesion throughout the T1 vertebra. Initial biopsy showed amyloid deposition and staging evaluation found localized disease. Prior to planned surgery and radiation the following year, she had worsening neuropathy including multiple falls. Repeat MRI confirmed lesion progression with concern for cord compression. Urgent surgical resection was performed. Histology showed numerous plasma cells with abundant amyloid deposition that was found by amyloid typing to be lambda light chain. An incidental B-cell rich lymphoid aggregate was also seen in a bone marrow fragment that required additional immunohistochemical evaluation, showing the aggregate to be benign while revealing the plasma cells to be positive for cyclin D1. She received localized radiation and has been asymptomatic.

DISCUSSION

Amyloidosis and plasma cell neoplasms require appropriate staging evaluation. The cyclin D1-positive plasma cells raises the possibility of the t(11;14)/IGH::CCND1 translocation that portends better prognosis and therapeutic response with venetoclax.

CONCLUSION

Amyloidomas are uncommon and may present in nearly any site, requiring a high index of clinical suspicion for proper diagnosis.

In vivo tracking of ex vivo generated 89 Zr-oxine labeled plasma cells by PET in a non-human primate model

B cells are an attractive platform for engineering to produce protein-based biologics absent in genetic disorders, and potentially for the treatment of metabolic diseases and cancer. As part of pre-clinical development of B cell medicines, we demonstrate a method to collect, ex vivo expand, differentiate, radioactively label, and track adoptively transferred non-human primate (NHP) B cells. These cells underwent 10- to 15-fold expansion, initiated IgG class switching, and differentiated into antibody secreting cells. Zirconium-89-oxine labeled cells were infused into autologous donors without any preconditioning and tracked by PET/CT imaging. Within 24 hours of infusion, 20% of the initial dose homed to the bone marrow and spleen and distributed stably and equally between the two. Interestingly, approximately half of the dose homed to the liver. Image analysis of the bone marrow demonstrated inhomogeneous distribution of the cells. The subjects experienced no clinically significant side effects or laboratory abnormalities. A second infusion of B cells into one of the subjects resulted in an almost identical distribution of cells, suggesting a non-limiting engraftment niche and feasibility of repeated infusions. This work supports the NHP as a valuable model to assess the potential of B cell medicines as potential treatment for human diseases.

Lymphoid aggregates in the bone marrow biopsies of patients with myelodysplastic syndromes - A potential prognostic marker?

Background

Lymphoid aggregates (LA) are occasionally seen in bone marrow biopsies (BMB) of myelodysplastic syndromes (MDS) patients. Our aim was to evaluate their incidence and association with prognosis.

Methods

We compared BMB reports of MDS patients treated at the Tel Aviv Sourasky Medical Center (2011-2018), and controls (2015-2017, normal BMB), and examined the charts of the MDS patients (LA+ and LA-). Categorical, normally and non-normally distributed continuous variables were compared using Fisher's exact, independent t and Mann-Whitney tests respectively. Adjusted [age, gender, lymphocytes, white blood cells (WBC) and diabetes mellitus (DM)] Cox proportional hazard model examined survival at 12 and 24 months.

Results

MDS patients (N=140) were older than controls (N=38; 74.1 vs 69.2 years, p=0.005); 34 MDS (24.3%) and 5 controls (13.2%) had LA+ (P=0.141). CD20/CD3 staining suggested LA polyclonality. MDS/LA+ (vs MDS/LA-) patients were younger, with a trend (not statistically significant) towards poor prognostic parameters: lower Hb, WBC, and platelets, higher LDH, BM cellularity, and IPSS-R score. The incidence of cardiovascular disease was similar, but MDS/LA+ had twice the incidence of DM (38.2% vs 19.0%, p=0.022). Similar trend for cancer (26.5% vs 14.3%, p=0.102). Twelve-month survival: 24/34 (70.6%) MDS/LA+; 88/106 (83.0%) MDS/LA- (p=0.140). This trend, seen in Kaplan-Meier curves, disappeared at 24 months. The hazard ratio for LA was 2.283 (p=0.055) for 12 months.

Conclusion

These preliminary data suggest LA are relatively common (24%) in MDS BMB, and might indicate poor prognosis. This may reflect involvement of the immune system in MDS. Future studies will examine larger groups, to clarify the incidence, significance and the pathophysiology.

Role of immunoglobulin heavy and light chain gene rearrangement analysis in differentiating between benign and malignant bone marrow B-cell lymphoid aggregates

Lymphoid aggregates are found in a minority of bone marrow biopsy and aspirate specimens, and when present, the distinction between benign and malignant aggregates can represent a diagnostic challenge. Morphologic and immunophenotypic evaluation of the aggregates can aid in that distinction but in a few cases, detection of immunoglobulin heavy chain (IGH) and kappa light chain (IGK) gene rearrangements may be needed to rule in or out a malignant disease process. We studied the role of testing for IGH/IGK rearrangements in the distinction between benign and malignant B cell-predominant lymphoid aggregates. Only a few studies have addressed this issue and most lacked an adequate number of cases for establishing statistical significance. Our study retrospectively evaluated 120 bone marrow aspirate and biopsy specimens, 79 cases originally diagnosed with benign lymphoid aggregates [4,5], and 41 demonstrating a B-cell lymphoma with malignant aggregates. Immunohistochemical stains were performed on all cases in our study and flow cytometry results were available in the vast majority of cases (98%). All patients included in our study but 9 had at least 2 years of clinical follow-up information. Of the malignant lymphoma cases, IGH/IGK rearrangements were demonstrated by polymerase chain reaction in 60% of the cases. Moreover, clonal rearrangements were identified in 15% of the cases with benign aggregates. After at least 2 years of follow-up, only one case with a positive clonality study occurring in the setting of morphologically benign-appearing bone marrow lymphoid aggregates experienced a relapse of non-Hodgkin lymphoma. Molecular analysis of the IGH and IGK genes may have utility in confirming the presence of malignancy in bone marrow aspirates and biopsy specimens. False-negative results, however, are possible due to testing limitations and sampling issues. Moreover, patients with conditions such as autoimmune disorders or infectious diseases are shown to also develop clonal B-cell lymphoid aggregates. As a result, we recommend a thorough morphological examination, informative immunohistochemical staining, accurate flow cytometric analysis, and current IGH/IGK rearrangement testing when evaluating bone marrow specimens containing B cell-predominant lymphoid aggregates, with the knowledge that molecular clonality results should be carefully interpreted in the context of morphological and immunophenotypic findings to prevent misdiagnosis.

Lymphoid aggregates in bone marrow: a diagnostic pitfall

Lymphoid aggregates in bone marrow specimens are a relatively frequent finding that may pose a diagnostic challenge for a pathologist. The distinction between reactive and neoplastic aggregates has significant clinical relevance. Although many testing modalities such as immunohistochemistry, flow cytometry and molecular studies are currently available in clinical laboratories, the appropriate utilisation of these modalities and the awareness of their potential pitfalls are important. When a neoplastic process is ruled out, the significance of benign lymphoid aggregates in bone marrow is often unclear, as they may be associated with a broad spectrum of conditions including infections, autoimmune disorders, medications, or may even be idiopathic.This review focuses on evidence-based criteria that can aid in making the distinction between benign and malignant lymphoid aggregates and discusses the advantages, disadvantages and limits of ancillary tests used for this purpose. Finally, the most common aetiologies of benign lymphoid aggregates and their associations with specific diseases are discussed.

Challenges Encountered and Pattern-Based Analysis of Bone Marrow Biopsy in Lymphomas: An Institutional Experience

Objective The evaluation of bone marrow (BM) status is an integral part of the initial workup of patients diagnosed with lymphoma as it plays an important role in staging and predicting prognosis in these patients. This article determines the incidence and pattern of BM involvement in lymphoma cases and distinguishes benign from malignant lymphoid aggregates in BM biopsies.

Materials and Methods The study group included 121 cases of Hodgkin and non-Hodgkin lymphomas for which BM biopsies were performed, fixed in acetic acid-zinc formalin solution, decalcified using 10% formic acid, and subjected to hematoxylin and eosin and immunohistochemistry.

Results The overall incidence of BM biopsy involvement in our study was 31.4% (37/118), including 34.7% (35/101) in cases of B cell lymphomas, 25% (2/8) in cases of T cell lymphomas, and no involvement in Hodgkin lymphoma. The predominant histological pattern of BM involvement was diffused (14/37; 37.8%), followed by interstitial (10/37; 27.1%). Five cases revealed benign nonparatrabecular lymphoid aggregates which could be confused with lymphomatous involvement, especially in low grade lymphomas.

Conclusion A careful examination of the BM biopsies along with clinical history, peripheral blood examination, flow cytometry, and immunohistochemistry will help in arriving at the correct diagnosis.

Mast cell neoplasm: a challenging pathological diagnosis

Systemic mastocytosis (SM) is a myeloid neoplasm characterized by abnormal growth and accumulation of neoplastic mast cells in at least one extracutaneous site. Clinical presentation and course are variable, most patients developing an indolent disease and some, an aggressive/leukemic form. Because of its rarity, most physicians are unfamiliar with this disease and do not readily diagnose it. In the present retrospective study, the authors describe 12 patients diagnosed with mast cell neoplasm. Cases were selected from three institutions from Campinas and São Paulo City, Brazil. Morphological features and diagnostic pitfalls are emphasized. Patients' age ranged from 15 to 81 years (mean 51.6 years). Male and female were affected similarly (1:1). Ten patients were classified as aggressive systemic mastocytosis (SM), one patient as SM with an associated acute promyelocytic leukemia with t(15;17), and one patient with mast cell sarcoma. Most common clinical findings included anemia (9 patients), thrombocytopenia (3 patients) and skin lesions (3 patients). Bone marrow was involved in 11 patients at diagnosis, followed by skin (5 patients). Five morphological patterns were present: mast cell aggregates (5), plasmacytoid (4), monocytoid (2), spindle cell (2) and epithelioid/pleomorphic (1); two patients showed two histological patterns. In all cases neoplastic cells were positive for CD117/C-KIT. C-KIT D816V mutation was present in four patients, C-KIT K509I in two, and del(7q22) in one; in five cases no mutational status was available. Despite limited resources, basically morphology and a restricted immunohistochemical panel, it is possible to diagnose mast cell neoplasm. Of note, pathologist should recognize the different morphological variants of the disease and include the adequate markers when requesting immunohistochemical studies.

The immunity features and defects against primary cytomegalovirus infection post-splenectomy indicate an immunocompromised status: A PRISMA-compliant meta-analysis

BACKGROUND

To evaluate if splenectomy results in severely impaired immune responses against primary cytomegalovirus (CMV) infection compared to the general immunocompetent population.

METHODS

We performed a systemic literature review to study CMV infections in splenectomized individuals, a special population group presently considered immunocompetent to viral infections. We retrieved 30 cases with established CMV infection post-splenectomy and we recorded their disease manifestations, laboratory findings, immunological studies, and histopathology reports. In addition, we retrieved numerous multidisciplinary articles in view of post-splenectomy immunology defects, as well as of immune responses to primary invading CMV in the absence of the spleen. Two clinical studies directly comparing splenectomized with nonsplenectomized individuals under severe iatrogenic immunosuppression as well as the numerically largest review articles of CMV infections in immunocompetent were retained.

RESULTS

Splenectomy results in the loss of spleen's ability to fend-off blood-borne pathogens and impairs the link between innate and adaptive immunity. The major post-splenectomy immune-defects against CMV are: weakened, delayed or absent anti-CMV IgM, and compensatory marked IgG response; severely impaired B-cell and CD4, CD8 T-cells function responses; and post-splenectomy, bone marrow compensates for the absence of spleen's immune responses against CMV, mimicking a monoclonal T-cell lymphoproliferative process.

CONCLUSION

The puzzled diagnosis of the CMV syndrome post-splenectomy is of the most challenging and misleading, resulting in risky and costly interventions and a subsequent prolonged hospitalization (2 months). The mounting multi-disciplinary literature evidence renders us to suggest that splenectomized individuals are not only prone to encapsulated bacteria but also behave as immunocompromised to CMV.

Constitutive overexpression of TNF in BPSM1 mice causes iBALT and bone marrow nodular lymphocytic hyperplasia

BPSM1 (Bone phenotype spontaneous mutant 1) mice develop severe polyarthritis and heart valve disease as a result of a spontaneous mutation in the Tnf gene. In these mice, the insertion of a retrotransposon in the 3' untranslated region of Tnf causes a large increase in the expression of the cytokine. We have found that these mice also develop inducible bronchus-associated lymphoid tissue (iBALT), as well as nodular lymphoid hyperplasia (NLH) in the bone marrow. Loss of TNFR1 prevents the development of both types of follicles, but deficiency of TNFR1 in the hematopoietic compartment only prevents the iBALT and not the NLH phenotype. We show that the development of arthritis and heart valve disease does not depend on the presence of the tertiary lymphoid tissues. Interestingly, while loss of IL-17 or IL-23 limits iBALT and NLH development to some extent, it has no effect on polyarthritis or heart valve disease in BPSM1 mice.

Intravascular T-cell lymphoma in a patas monkey (Erythrocebus patas)

A 9-year-old female captive patas monkey (Erythrocebus patas) presented with poor general condition, inability to stand, petechiae, anaemia, thrombocytopenia, and leukocytosis. Due to poor response to treatment, the animal was euthanized 16 days later. Postmortem examination revealed hemorrhages in several organs and bilateral cerebral infarctions. Histologically, prominent accumulations of large neoplastic lymphocytes in cerebral and meningeal blood vessels were demonstrated within the lesions and in other organs (e.g., bone marrow, ovary, intestine). Immunohistochemically, neoplastic cells expressed CD3 and Ki-67. PCR revealed a lymphocryptovirus (LCV) infection, while Epstein–Barr nuclear antigen 2 (EBNA2) could not be demonstrated within neoplastic cells by means of immunohistochemistry. Based on the pathological findings, an intravascular lymphoma (IVL) of T-cell origin was diagnosed. To the authors' knowledge, this is the first report on this rare entity in a nonhuman primate.

The prognostic significance of monoclonal immunoglobulin gene rearrangement in conjunction with histologic B-cell aggregates in the bone marrow of patients with diffuse large B-cell lymphoma

Bone marrow involvement (BMI) is a well‐known poor prognostic factor in patients with diffuse large B‐cell lymphoma (DLBCL). This study robustly investigated the significance of monoclonal immunoglobulin gene rearrangement combined with histologic B‐cell aggregates in bone marrow (BM) in the detection of a poor prognostic group. Pretreatment BM samples of 394 DLBCL patients were analyzed via the immunoglobulin gene rearrangement study and the microscopic examination. Monoclonal immunoglobulin gene rearrangement was detected in 25.4% of cases. Histologic B‐cell aggregates with the features of large B‐cell lymphoma aggregates, small cell B‐cell lymphoma aggregates, or B‐cell aggregates of unknown biological potential were observed in 12% of cases (6.9%, 1.3%, and 3.8%, respectively). Histologic B‐cell aggregates were more associated with monoclonality than polyclonality. Cases with both monoclonality and histologic B‐cell aggregates demonstrated close association with poor prognostic factors such as a higher International Prognostic Index score and showed an inferior overall survival rate when compared to cases with only monoclonality or only histologic B‐cell aggregates. From the findings, a combination of monoclonality and histologic B‐cell aggregates within the bone marrow was highly associated with poor prognosis and could be used to determine high‐risk DLBLC patients with greater sensitivity and specificity than conventional microscopic examination or immunoglobulin gene rearrangement study alone.

Differentiating Benign From Malignant Bone Marrow B-Cell Lymphoid Aggregates: A Statistical Analysis of Distinguishing Features

Context

Lymphoid aggregates are seen in a minority of bone marrow biopsy specimens, and when present, their neoplastic nature is often apparent by morphologic evaluation. However, the distinction between benign and malignant aggregates can be a diagnostic challenge when there are multiple aggregates with no documented history of lymphoma.

Objective

To aid in the distinction between benign and malignant B-cell lymphoid aggregates.

Design

Previously, we described specific distribution patterns for B and T lymphocytes within bone marrow aggregates. To statistically analyze the significance of these patterns as well as previously reported criteria, we examined 128 bone marrow specimens with benign aggregates and 78 specimens with documented malignant B-cell aggregates and calculated specific odds ratios (ORs) and 95% confidence intervals (CIs) to aid in differentiating between benign and malignant B-cell aggregates.

Results

Aggregates with infiltrative edges (OR, 80.54; 95% CI, 31.76–204.21), a B-cell pattern (OR, 30.08; 95% CI, 13.28–68.10), paratrabecular location (OR, 10.17; 95% CI, 3.96–26.12), size greater than 600 μm (OR, 6.83: 95% CI, 3.61–12.93), or cytologic atypia correlated with malignancy.

Conclusion

When taken collectively, the presence of more than 2 of these characteristic features was strongly predictive of malignancy.