Colonic adenomatous polyp with florid presence of monoclonal lambda Russell bodies: Case report and etiopathogenic hypothesis.

Russell bodies (RBs) are round eosinophilic intracytoplasmic inclusions formed by condensed immunoglobulins in mature plasma cells, which are called Mott cells. These cells are rarely found in the gastric tract, with even less cases reported in the colorectal region. There are still many questions about this event, as it is still unknown the relationship between the agents reported of increasing the probability of appearance of these cells and the generation of RBs. In this case report we describe the fifth patient presenting an infiltration of Mott cells in a colorectal polyp, being the second case with a monoclonal origin without a neoplastic cause, and the first one monoclonal for lambda. A comparison with previously similar reported cases is also done, and a possible etiopathogenic hypothesis proposed.

Circulating plasma cells as a predictive biomarker in Multiple myeloma: an updated systematic review and meta-analysis.

BACKGROUND: Circulating plasma cells (CPCs) are defined by the presence of peripheral blood clonal plasma cells, which would contribute to the progression and dissemination of multiple myeloma (MM). An increasing number of studies have demonstrated the predictive potential of CPCs in the past few years. Therefore, there is a growing need for an updated meta-analysis to identify the specific relationship between CPCs and the prognosis of MM based on the current research status. METHODS: The PubMed, Embase, and Cochrane Library databases were screened to determine eligible studies from inception to November 5, 2023. Publications that reported the prognostic value of CPCs in MM patients were included. Hazard ratios (HRs) with 95% confidence intervals (CIs) of overall survival (OS) and progression-free survival (PFS) were extracted to pool the results. Subgroup analyses were performed based on region, sample size, cut-off value, detection time, initial treatment, and data type. The association between CPCs level and clinicopathological characteristics, including the International Staging System (ISS), Revised-ISS (R-ISS), and cytogenetic abnormalities were also evaluated. Statistical analyses were conducted using STATA 17.0 software. RESULTS: Twenty-two studies with a total of 5637 myeloma patients were enrolled in the current meta-analysis. The results indicated that myeloma patients with elevated CPCs were expected to have a poor OS (HR = 2.19, 95% CI: 1.81-2.66, p < 0.001) and PFS (HR = 2.45, 95% CI: 1.93-3.12, p < 0.001). Subgroup analyses did not alter the prognostic role of CPCs, regardless of region, sample size, cut-off value, detection time, initial treatment, or data type. Moreover, the increased CPCs were significantly related to advanced tumour stage (ISS III vs. ISS I-II: pooled OR = 2.89, 95% CI: 2.41-3.46, p < 0.001; R-ISS III vs. R-ISS I-II: pooled OR = 3.65, 95% CI: 2.43-5.50, p < 0.001) and high-risk cytogenetics (high-risk vs. standard-risk: OR = 2.22, 95% CI: 1.60-3.08, p < 0.001). CONCLUSION: Our meta-analysis confirmed that the increased number of CPCs had a negative impact on the PFS and OS of MM patients. Therefore, CPCs could be a promising prognostic biomarker that helps with risk stratification and disease monitoring.

There is a growing need for an updated meta-analysis to identify the specific relationship between CPCs and the prognosis of MM based on the current research status.Our meta-analysis revealed that a high CPCs level was significantly associated with worse OS and PFS in MM patients.CPCs could be a promising predictive biomarker that helps with risk stratification and disease monitoring.

Case of IgG4-related Disease with Crescentic Glomerulonephritis: An Unusual Presentation of the Disease.

IgG4-related disease (IgG4-RD) is a chronic systemic inflammatory  disease, characterized by tissue infiltration of lymphocytes and  IgG4-secreting plasma cells, presenting by fibrosis of different  tissues, which is usually responsive only to oral steroids therapy.  Kidneys are the most commonly involved organs, exhibiting renal  insufficiency, tubulointerstitial nephritis, and glomerulonephritis.  Here, we describe a patient with acute renal insufficiency who  was presented with edema, weakness, anemia and multiple  lymphadenopathies. Kidney and lymph node biopsy showed  crescentic glomerulonephritis in kidneys and lymphoplasmacytic  infiltration in lymph nodes. After a course of treatment with an  intravenous pulse of corticosteroid and cyclophosphamide, the  patient's symptoms subsided, and kidney function improved. DOI: 10.52547/ijkd.7788.

Chronic sclerosing sialadenitis of the bilateral submandibular glands in childhood - a diagnostic dilemma.

Chronic sclerosing sialadenitis (CSS), currently included in the group of immunoglobulin G4 (IgG4)-related diseases, is an under-recognized inflammatory lesion that afflicts mostly the submandibular gland of 40-60 years adults. To our knowledge, only one case of CSS located in the submandibular gland has been reported in childhood to date. We present a case of CSS in a 5-year-old male child. He presented with bilateral submandibular swellings that clinically resembled discrete lumps, suspected to be tumors. The completely resected tumors composed predominantly of dense lymphoplasmacytic inflammatory infiltrate rich in IgG4-positive cells [77-90 IgG(+) cells per high-power field; IgG4(+)∕IgG(+) cells ratio of 42.77%]. We discuss the peculiarities of this case, and we also review the literature on CSS.

Different evasion strategies in multiple myeloma.

Multiple myeloma is the second most common malignant hematologic malignancy which evolved different strategies for immune escape from the host immune surveillance and drug resistance, including uncontrolled proliferation of malignant plasma cells in the bone marrow, genetic mutations, or deletion of tumor antigens to escape from special targets and so. Therefore, it is a big challenge to efficiently treat multiple myeloma patients. Despite recent applications of immunomodulatory drugs (IMiDS), protease inhibitors (PI), targeted monoclonal antibodies (mAb), and even hematopoietic stem cell transplantation (HSCT), it remains hardly curable. Summarizing the possible evasion strategies can help design specific drugs for multiple myeloma treatment. This review aims to provide an integrative overview of the intrinsic and extrinsic evasion mechanisms as well as recently discovered microbiota utilized by multiple myeloma for immune evasion and drug resistance, hopefully providing a theoretical basis for the rational design of specific immunotherapies or drug combinations to prevent the uncontrolled proliferation of MM, overcome drug resistance and improve patient survival.

Myelomatous pleural effusion in multiple myeloma- A rare presentation.

Multiple myeloma is a malignant plasma cell condition that mostly affects the skeletal system and bone marrow. Pleural effusions are uncommon and typically result from other conditions coexisting with multiple myeloma. Malignant myelomatous pleural effusions are rare complications of multiple myeloma, occurring in less than 1% of patients and are associated with poor prognosis having mean survival of less than 4 months. The present case report is a 41-year-old multiple myeloma patient who developed bilateral pleural effusion at a disease relapse. Chemotherapeutic regimen of cyclophosphamide, bortezomib, and dexamethasone given. Despite a positive response to treatment, the patient's condition worsened over the course of following month and he eventually passed away. Myelomatous pleural effusion indicates poor prognosis and early consideration helps in quick diagnosis and initiation of treatment which may help in improving prognosis.

Increased frequency of oral plasma cell mucositis/plasma cell gingivitis after the COVID-19 pandemic: a 23-year retrospective analysis and review of diagnostic challenges relating to this condition.

OBJECTIVE: Oral plasma cell mucositis (PCM) or localized plasma cell gingivitis (PCG) is an idiopathic inflammatory condition often associated with hypersensitivity reactions. This study aimed to evaluate the frequency and features of PCM/PCG in a large biopsy service over a time period of more than 20 years. STUDY DESIGN: The biopsy archives at University of Florida College of Dentistry were searched from 2000 through the first quarter of 2023 for cases of oral PCM or PCG. Case data were aggregated and analyzed. RESULTS: A total of 107 cases were included. Between 2000 and 2019, PCM/PCG was diagnosed in 0.03% of all biopsy cases. Starting in 2020 through 2023, the percentage of biopsies diagnosed as PCM/PCG increased threefold to 0.10% of all biopsy cases, and the mean patient age increased by 3 years. There were no statistically significant differences between cases diagnosed from 2000 to 2019 and those from 2020 to 2023 regarding age, sex, location, or histology. CONCLUSIONS: A significant increase in PCM/PCG was identified in this study at one institution coinciding with the start of the COVID-19 pandemic. Further investigation is recommended to determine if this is a widespread phenomenon and identify possible etiologic mechanisms.

Plasmablastic lymphoma: current knowledge and future directions.

Plasmablastic lymphoma (PBL) is an aggressive non-Hodgkin lymphoma associated with HIV infection and immunodeficiency. However, PBL can also be seen immunocompetent individuals in recent studies. PBL was characterized by distinct clinical and pathological features, such as plasmablastic morphology and universal expression of plasma cell markers. The clinicopathologic features were different between HIV-negative and HIV-positive patients. Gene expression analysis identified the unique molecular feature in PBL, including frequent c-MYC rearrangement and downregulation of BCR signaling pathway. Despite the recent advances in the treatment of PBL, the prognosis of PBL patients remains dismal. The objectives of this review are to summarize the current knowledge on the epidemiology, molecular profiles, clinical and pathological features, differential diagnosis, treatment strategies, prognostic factors, and potential novel therapeutic approaches in PBL patients.

Diagnosis and management of smouldering myeloma: A British Society for Haematology Good Practice Paper.

Multiple myeloma is a bone marrow-based plasma cell tumour that develops from asymptomatic pre-cursor conditions smouldering myeloma and monoclonal gammopathy of uncertain significance and all are characterised by the presence of a monoclonal protein in the blood. Diagnosis and distinction between these conditions is based on blood tests, the bone marrow biopsy and cross sectional imaging. There are various risk stratification models that group patients with smouldering myeloma into risk groups based on risk of progression to symptomatic disease. Management is mainly observational for patients with smouldering myeloma although clinical trials for high-risk disease may be available. Restaging is required if evidence for progression.

Imaging flow cytometric detection of del(17p) in bone marrow and circulating plasma cells in multiple myeloma.

BACKGROUND: Detection of del(17p) in myeloma is generally performed by fluorescence in situ hybridization (FISH) on a slide with analysis of up to 200 nuclei. The small cell sample analyzed makes this a low precision test. We report the utility of an automated FISH method, called "immuno-flowFISH", to detect plasma cells with adverse prognostic risk del(17p) in bone marrow and blood samples of patients with myeloma. METHODS: Bone marrow (n = 31) and blood (n = 19) samples from 35 patients with myeloma were analyzed using immuno-flowFISH. Plasma cells were identified by CD38/CD138-immunophenotypic gating and assessed for the 17p locus and centromere of chromosome 17. Cells were acquired on an AMNIS ImageStreamX MkII imaging flow cytometer using INSPIRE software. RESULTS: Chromosome 17 abnormalities were identified in CD38/CD138-positive cells in bone marrow (6/31) and blood (4/19) samples when the percent plasma cell burden ranged from 0.03% to 100% of cells. Abnormalities could be identified in 14.5%-100% of plasma cells. CONCLUSIONS: The "immuno-flowFISH" imaging flow cytometric method could detect del(17p) in plasma cells in both bone marrow and blood samples of myeloma patients. This method was also able to detect gains and losses of chromosome 17, which are also of prognostic significance. The lowest levels of 0.009% (bone marrow) and 0.001% (blood) for chromosome 17 abnormalities was below the detection limit of current FISH method. This method offers potential as a new means of identifying these prognostically important chromosomal defects, even when only rare cells are present and for serial disease monitoring.

Retrospective Case Series of Cocaine-Associated Plasma Cell Orificial Mucositis.

Importance: Plasma cell orificial mucositis (PCOM) associated with cocaine use is an emerging, rare condition that has become a concern in Spain in recent years. Limited knowledge exists regarding this novel condition. Objectives: To delineate the clinicopathologic characteristics of this emerging entity and establish a novel approach in the differential diagnosis of cocaine-associated lesions. Design, Setting, and Participants: A descriptive, retrospective, multicenter case series of 10 patients diagnosed with cocaine-associated PCOM was conducted in Spain from April 2020 to March 2023. Main Outcomes and Measures: Patient demographic, clinical, histopathologic, and treatment data were collected. Results: A total of 10 patients (6 [60%] male; median [range] age, 45.5 [36-66] years) presenting with exudative ulcerated plaques were identified for this study. The lesions had raised and erythematous edges over the nostril and a median (range) evolution time of 9 (2-24) months. Septal or palate perforations were observed in 4 (40%) of the patients. Biopsies revealed a dense inflammatory infiltrate of plasma cells in the dermis without atypia and with eosinophils. All patients reported recent cocaine use. Three urine tests detected cocaine but found no presence of amphetamines or opiates. Six patients improved with corticosteroid therapy. Up to 60% of patients were lost to follow-up. Conclusions and Relevance: This case series describes the clinicopathologic characteristics of PCOM, an emerging entity associated with cocaine use in Spain, and demonstrates a novel approach in the differential diagnosis of cocaine-associated lesions. To date, cocaine-associated skin lesions have been reported as neutrophilic dermatoses and vasculitis. The appearance of a plasma cell infiltrate changes what has been described in the medical literature so far. PCOM is a benign condition of unknown cause characterized by a proliferative polyclonal plasma cell infiltrate. A comprehensive differential diagnosis workup is required to reach this exclusionary diagnosis. Several irritants have been documented in cases of PCOM, and a hypersensitivity mechanism has been proposed. Since the initial report of cocaine-associated PCOM in Spain, its incidence has experienced a surge in the country. The cause of this phenomenon may be attributed to newly unidentified adulterants. The administration of corticosteroids and discontinuation of cocaine use are the sole treatments that have demonstrated efficacy. Clinicians should be vigilant regarding this emerging condition and conduct inquiries into cocaine use. Additional research is required to clarify the pathophysiology of this emerging condition.

Challenging diagnosis of IgM multiple myeloma.

IgM monoclonal gammopathies such as IgM myeloma and Waldenström macroglobulinaemia are distinct haematological conditions; however, differentiating between these entities can often present as a challenge.In this review, we explore the challenging diagnosis and treatment of IgM myeloma in a patient presenting with unexplained macrocytic anaemia, elevated serum protein and IgM levels in the absence of t(11;14) and lytic bone lesions that are classically associated with the diagnosis of IgM myeloma. The diagnosis was established based on 40% monoclonal plasma cell population on a bone marrow biopsy, gain of 1q21 on fluorescence in situ hybridisation, cyclin D1 positivity and absence of MYD88 mutation.

Prognostic value of circulating plasma cells detected by flow cytometry in newly diagnosed multiple myeloma patients: a systematic review and meta-analysis.

OBJECTIVES: Multiple myeloma (MM) is a malignant plasma cell disorder. The most widely accepted staging system for MM is the revised International Staging System based on cytogenetic and clinical biomarkers. The circulating clonal plasma cells (CPCs) were reported to have potential prognostic impact on MM. Among various diagnostic approaches, multiparametric flow cytometry (FCM) offers heightened sensitivity, minimal invasiveness and reproducibility. We conducted a meta-analysis to evaluate the prognostic value of quantifying CPCs via FCM in newly diagnosed symptomatic MM (NDMM) patients. DESIGN: Systematic review and meta-analysis. DATA SOURCE: PubMed, Web of Science, Embase and references of included studies. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: We included observational studies that evaluated the prognostic value of CPCs detected by FCM in NDMM. DATA EXTRACTION AND SYNTHESIS: Data were screened and extracted independently by two investigators. The pooled results originated from random effects models. The primary endpoint was overall survival (OS). The secondary endpoint was progression-free survival (PFS). To evaluate the prognostic value of CPCs in NDMM, HRs and their 95% CI for both OS and PFS were derived using COX multivariable models. These values were then used to compute the pooled estimated effect. RESULTS: Our meta-analysis encompassed a total of 2704 NDMM patients from 11 studies up to 27 August 2022. The pooled HR for OS and PFS in CPC-positive (CPCs+) group and CPC-negative group were 1.95 (95% CI 1.24 to 3.07) and 2.07 (95% CI 1.79 to 2.39), respectively. The autologous stem cell transplantation (ASCT) failed to eliminate the adverse impact on OS and PFS. The heterogeneity may stem from the use of novel agents or traditional chemotherapy as initial treatment. CONCLUSION: This meta-analysis indicates CPCs+ had an adverse impact on the prognosis of NDMM patients in the total population, and the adverse impact could not be eliminated by ASCT. PROSPERO REGISTRATION NUMBER: CRD42021272381.

An interesting case of AL amyloidosis and MM: a complex scenario with cardiac involvement.

Our patient presented with complaints of progressive shortness of breath for 1 month. She was diagnosed with a case of infiltrative type of restrictive cardiomyopathy (RCM) based on echocardiography and cardiac MRI findings. Her fat pad biopsy was suggestive of AL type of amyloidosis (AL). She was diagnosed with a case of multiple myeloma (MM) based on bone marrow biopsy findings with 48% plasma cells and a skeletal survey with lytic bone lesions on the skull, thus meeting the Crab criteria. We want to highlight the complex nature of this case and the difficulties associated with making a diagnosis. This case report presents an excellent opportunity to touch on the interesting topics of RCM, amyloidosis and MM.

Unicentric Castleman Disease: Illustration of Its Morphologic Spectrum and Review of the Differential Diagnosis.

CONTEXT.­: Unicentric Castleman disease (UCD) is a dynamic entity with a wide spectrum of morphologic findings. UCD can be further subdivided into hyaline-vascular and mixed/plasmacytic variants. Hyaline-vascular UCD has both follicular and interfollicular (stromal) changes, and occasionally these lesions show a skewed representation of either the follicular or stromal compartments. Plasmacytosis is usually minimal in the hyaline-vascular variant. The mixed/plasmacytic variant of UCD is composed of sheets of plasma cells often associated with a variable number of follicles with regressive changes. OBJECTIVE.­: To illustrate the differential diagnosis of UCD, as it is quite broad and includes lymphomas, plasma cell neoplasms, stromal neoplasms such as follicular dendritic cell sarcoma and vascular neoplasms, immunoglobulin G4-related disease, infections, and other rare lesions. An additional objective is to enhance awareness of the morphologic features of UCD in excisional and in small core-needle biopsy specimens, the latter of which may inadvertently target follicle- or stroma-rich areas, causing diagnostic challenges. DATA SOURCES.­: In this review, we provide readers a concise illustration of the morphologic spectrum of UCD that we have encountered in our practice and a brief discussion of entities in the differential diagnosis. CONCLUSIONS.­: UCD exhibits a broad spectrum of morphologic changes, and awareness of these morphologic variations is key to avoid misdiagnosis.

Xanthogranulomatous Ureteritis: A Diagnostic Challenge in a Patient with Bladder Cancer.

Xanthogranulomatous ureteritis is a very rare process characterized by the presence of foamy histiocytes in a background of chronic active inflammation affecting the ureteral wall. Herein, we describe a case of a 64-year-old man with bladder cancer affecting the left posterolateral wall of the bladder. Radiologically, there was a suspicion of multifocal involvement of the ureteral wall. The patient underwent a radical cystectomy with bilateral pelvic lymphadenectomy and a laparoscopic left nephroureterectomy. Histopathologic examination of the radical cystectomy revealed an invasive high-grade urothelial carcinoma. The wall of the left ureter was replaced by abundant foamy histocytes and a mixed inflammatory infiltrate with lymphocytes and plasma cells consistent with xanthogranulomatous ureteritis. In this report, we highlight the importance of awareness of this benign process when observing a ureteral mass in cancer patients.

Antineutrophil Cytoplasmic Autoantibody-negative Pauci-immune Necrotizing Glomerulonephritis with Plasma Cell-rich Tubulointerstitial Nephritis Complicated with Pleuritis and Digital Ischemia.

Antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) predominantly affects small vessels. Almost all AAV patients are positive for myeloperoxidase- or proteinase 3-ANCA, and ANCA plays a crucial role in the pathogenesis of AAV. We herein report an ANCA-negative AAV patient with pauci-immune necrotizing glomerulonephritis and plasma cell-rich tubulointerstitial nephritis who was complicated with pleuritis and digital ischemia. ANCA-negative AAV is a rare clinical entity that is difficult to diagnose, and pleuritis and digital ischemia are rare manifestations of AAV. An early diagnosis and appropriate treatment are important, as any delay in the diagnosis may worsen the prognosis.

Assessment of specificity of dermatopathologic criteria for IgG4-related skin disease.

BACKGROUND: IgG4-related disease (IgG4-RD) represents a recently characterized multisystemic fibroinflammatory condition that can manifest a spectrum of skin findings (IgG4-related skin disease; IgG4-RSD). Histopathologic and immunohistochemical criteria have been proposed; however, the specificity of these criteria merits scrutiny given the potential histopathologic overlap of IgG4-RSD and both neoplastic and inflammatory skin conditions featuring lymphoplasmacytic infiltrates (IgG4-RSD mimics). This study sought to assess the specificity of the criteria by quantifying the frequency by which an expanded spectrum of IgG4-RSD mimics meet proposed thresholds. METHODS: Following IRB approval, a total of 69 cases of IgG4-RD mimics, representing 14 different diagnoses featuring plasma cells, were reviewed and analyzed for the following histopathologic and immunohistochemical features: (i) maximum IgG4+ count/high-powered field (hpf) >200; (ii) IgG4/IgG ratio >0.4 averaged over 3 hpfs; (iii) IgG4+ count >10 per hpf. RESULTS: Screening for IgG4-RSD by histopathologic criteria demonstrated the high frequency of lymphoplasmacytic infiltrates, contrasted with the rarity of storiform fibrosis (only one case of erythema elevatum diutinum [EED]) and obliterative phlebitis (0 cases). By immunohistochemical criteria, the analysis revealed that no cases exceeded 200 IgG4+ cells; 13% (9/69) cases demonstrated an IgG4/IgG ratio of >0.4 averaged over 3 hpfs; and 23% (16/69) cases demonstrated a mean IgG4+ count of >10 per hpf. CONCLUSION: Application of proposed IgG4-RSD histopathologic criteria to an expanded spectrum of potential IgG4-RSD mimics (to include cutaneous marginal zone lymphoma, syphilis, necrobiosis lipoidica, lichen sclerosus, ALHE, psoriasis, lymphoplasmacytic plaque, EED, and erosive pustular dermatosis), highlights the relative nonspecificity of lymphoplasmacytic infiltrates contrasted with the stringency of storiform fibrosis and obliterative fibrosis. Furthermore, an IgG4+ cell count of >10 per hpf and an IgG4/IgG ratio of >0.4 are not specific to IgG4-RSD alone. In the appropriate clinical context for IgG4-RSD, histopathologic features still represent the entry threshold for diagnosis consideration, which then allows for further screening by immunohistochemical criteria.

A rare case of secondary cutaneous lymphoplasmacytic lymphoma clinically presenting as acquired cutis laxa.

Lymphoplasmacytic lymphoma (LPL) is a rare variant of non-Hodgkin lymphoma, accounting for <1% of cases. Skin involvement in LPL is quite rare-accounting for approximately 5% of extramedullary disease-and includes a variety of clinical morphologies, such as erythematous-to-violaceous plaques, violaceous nodules or tumors, and ulceration at various anatomical sites. Herein, we report the case of a 45-year-old Korean woman who presented with generalized erythematous indurated plaques and pendulous skin growths, which were asymptomatic, with marked diffuse infiltration of lymphocytes and plasma cells in the dermis. Immunohistochemical studies revealed that the lymphoid cells expressed CD3, CD79a, and cytoplasmic IgG, but lacked CD10 and IgM. Moreover, kappa light chain restriction and monoclonal immunoglobulin heavy chain gene rearrangement were observed. Upon further workup, lymphoma involvement was reported in multiple lymph nodes, including those in the cervical and axillary regions. This case shows a unique form of cutaneous LPL clinically presenting as acquired cutis laxa, emphasizing the dermatologists' need to be vigilant for variant forms of this disease.

Evaluation of a new technique using artificial intelligence for quantification of plasma cells on CD138 immunohistochemistry.

INTRODUCTION: The diagnosis of plasma cell neoplasms depends on the accurate quantification of plasma cells, traditionally done by immunohistochemical CD138 staining of bone marrow biopsies. Currently, there is no fully satisfactory reference method for this quantification. In our previous study, we compared the commonly used overview estimation method (method A) with a novel method for counting plasma cells in three representative areas (method B). Results showed comparable concordance parameters between the two methods. In this follow-up study, we compared the previously evaluated methods with a digital analysis method (method C) that uses artificial intelligence in open-source software, QuPath. METHODS: Archived CD138 immunohistochemically stained trephine sections of bone marrow samples used in our previous study were used (n = 33). Reviewers selected three representative areas on each sample by taking images with a light microscope and camera. Digital analysis was performed using the positive cell detection function in QuPath. The entire process was repeated by each reviewer to test intraobserver concordance (concordance correlation coefficient [CCC]) in addition to interobserver concordance (intraclass correlation coefficient [ICC]). RESULTS: Intraobserver concordance of method C showed strong agreement for all reviewers with the lowest CCC = 0.854. Interobserver concordance for method C using ICC was 0.909 and 0.949. This showed high interobserver agreement with significant differences between method C and previously assessed method A (ICC = 0.793 and 0.713) and method B (ICC = 0.657 and 0.658). CONCLUSION: We were able to successfully count CD138-positive plasma cells in bone marrow biopsies using artificial intelligence. This method is superior to both manual counting and overview estimation, regardless of tumour load.