Daratumumab-based regimens for patients with multiple myeloma plus extramedullary plasmacytomas or paraskeletal plasmacytomas: initial follow-up of an Italian multicenter observational clinical experience.

Myeloma with extramedullary plasmacytomas not adjacent to bone (EMP) is associated with an extremely poor outcome compared with paraosseous plasmacytomas (PP) as current therapeutic approaches are unsatisfactory. The role of new molecules and in particular of monoclonal antibodies is under investigation. To determine whether daratumumab-based regimens are effective for myeloma with EMP, we report herein an initial multicenter observational analysis of 102 myeloma patients with EMP (n = 10) and PP (n = 25) at diagnosis and EMP (n = 28) and PP (n = 39) at relapse, treated with daratumumab-based regimens at 11 Haematological Centers in Italy.EMP and PP at diagnosis were associated with higher biochemical (90% vs. 96%, respectively) and instrumental ORR (86% vs. 83.3%, respectively), while at relapse, biochemical (74% vs. 73%) and instrumental (53% vs. 59%) ORR were lower. Median OS was inferior in EMP patients compared with patients with PP both at diagnosis (21.0 months vs. NR) (p = 0.005) and at relapse (32.0 vs. 40.0 months) (p = 0.428), although, during relapse, there was no statistically significant difference between the two groups. Surprisingly, at diagnosis, median TTP and median TTNT were not reached either in EMP patients or PP patients and during relapse there were no statistically significant differences in terms of median TTP (20 months for two groups), and median TTNT (24 months for PP patients vs. 22 months for EMP patients) between the two groups. Median TTR was 1 month in all populations.These promising results were documented even in the absence of local radiotherapy and in transplant-ineligible patients.

Septal plasmacytoma: Dilemma of diagnosis.

Plasmacytomas are malignant tumours characterised by abnormal monoclonal proliferation of plasma cells. They may be osseous or may arise from soft tissues. Extramedullary plasmacytoma (EMP) accounts for only 1% of all head and neck malignancies. Septal plasmacytomas are extremely rare. Here, we report a case of an 80-year-old male patient with alocalised plasmacytoma arising from the nasal septum, which was resected endoscopically, with post-op radiotherapy and no recurrence in 1 year of follow-up. A multidisciplinary approach is required for the optimal diagnosis and management. It is essential to exclude any systemic involvement before arriving at a diagnosis of solitary plasmacytoma. Depending on lesion resectability, a combined therapy is the treatment of choice.

Expert review on soft-tissue plasmacytomas in multiple myeloma: definition, disease assessment and treatment considerations.

In this review, two types of soft-tissue involvement in multiple myeloma are defined: (i) extramedullary (EMD) with haematogenous spread involving only soft tissues and (ii) paraskeletal (PS) with tumour masses arising from skeletal lesions. The incidence of EMD and PS plasmacytomas at diagnosis ranges from 1·7% to 4·5% and 7% to 34·4% respectively. EMD disease is often associated with high-risk cytogenetics, resistance to therapy and worse prognosis than in PS involvement. In patients with PS involvement a proteasome inhibitor-based regimen may be the best option followed by autologous stem cell transplantation (ASCT) in transplant eligible patients. In patients with EMD disease who are not eligible for ASCT, a proteasome inhibitor-based regimen such as lenalidomide-bortezomib-dexamethasone (RVD) may be the best option, while for those eligible for high-dose therapy a myeloma/lymphoma-like regimen such as bortezomib, thalidomide and dexamethasone (VTD)-RVD/cisplatin, doxorubicin, cyclophosphamide and etoposide (PACE) followed by SCT should be considered. In both EMD and PS disease at relapse many strategies have been tried, but this remains a high-unmet need population.

Pomalidomide-dexamethasone for treatment of soft-tissue plasmacytomas in patients with relapsed / refractory multiple myeloma.

OBJECTIVE: The presence of plasmacytomas (Ps) in patients with multiple myeloma (MM) is associated with a poor outcome, both in patients treated conventionally and in patients treated with novel agents. Two types of plasmacytomas have being recognized: paraskeletal plasmacytomas (PPs) and extramedullary plasmacytomas (EMPs), being the incidence of EMPs lower but with worse prognosis. Our aim has been to analyze the efficacy of the pomalidomide-dexamethasone combination in this patient profile. METHOD: In the present study, the efficacy of pomalidomide and dexamethasone in 21 patients from nine hospitals of Catalonia (Spain), with relapsed or refractory MM and Ps, was analyzed. For this purpose, we describe the evolution of paraprotein in serum and urine and the size of plasmacytomas during treatment with pomalidomide-dexamethasone. RESULTS: While 34% of the patients achieved a paraprotein response, only two patients with PPs (9%) responded (RC and PR). There were no responses among patients with EMPs. The median progression-free survival from the start of treatment with pomalidomide/dexamethasone was only 1.7 months and the median overall survival of 4.5 months. CONCLUSION: In conclusion, pomalidomide and dexamethasone has limited efficacy in patients with advanced MM and soft-tissue plasmacytomas.

Clinical Course of a Patient With Kidney Failure Due to Isolated Bilateral Renal Extramedullary Plasmacytomas.

Plasmacytomas are rare immunoproliferative monoclonal plasma cell diseases of lymphoid lineage that may present in an isolated or systemic manner. Systemic involvement is much more common than occurrences isolated to a particular organ, and for this reason, it is imperative to rule out systemic involvement for osseous and nonosseous isolated neoplasms. These neoplasms present unique challenges due to their location, extent of involvement, vague presentation, and dearth of treatment protocol. We report the case of a 69-year-old man who developed chronic kidney disease stage 4 between 2009 and 2012. Precipitous kidney failure, anorexia, fatigue, and flank pain necessitated clinical follow-up that ultimately led to thorough imaging and bilateral kidney biopsy. Protein electrophoresis, immunohistochemistry, and immunofluorescence were all consistent with bilateral renal extramedullary plasmacytomas. Treatment recommendations are often limited to prior case successes; however, chemotherapy, radiation, and surgery are the mainstay of treatment. Although surgery or combined therapy provides the best results for patients, such options are unfeasible with bilateral kidney involvement. Therefore, a chemotherapy regimen, similar to that for multiple myeloma, was determined to be most reasonable. Treatment consisted of 4 cycles of a bortezomib, cyclophosphamide, and dexamethasone regimen. Three months following chemotherapy, kidney function returned to baseline levels.

Insertional hypermutation in mineral oil-induced plasmacytomas.

Unless stimulated by a chronic inflammatory agent, such as mineral oil, plasma cell tumors are rare in young BALB/c mice. This raises the questions: What do inflammatory tissues provide to promote mutagenesis? And what is the nature of mutagenesis? We determined that mineral oil-induced plasmacytomas produce large amounts of endogenous retroelements--ecotropic and polytropic murine leukemia virus and intracisternal A particles. Therefore, plasmacytoma formation might occur, in part, by de novo insertion of these retroelements, induced or helped by the inflammation. We recovered up to ten de novo insertions in a single plasmacytoma, mostly in genes with common retroviral integration sites. Additional integrations accompany tumor evolution from a solid tumor through several generations in cell culture. The high frequency of de novo integrations into cancer genes suggests that endogenous retroelements are coresponsible for plasmacytoma formation and progression in BALB/c mice.

Extramedullary Intracranial Plasmacytomas: A Systematic Review of Literature.

Extramedullary plasmacytoma (EMP) is an uncommon disorder characterized by the development of abnormal plasma cell tumors outside the bone marrow. These tumors are typically observed in various locations, including the upper respiratory tract, gastrointestinal tract, and other soft tissues. Among the less explored manifestations of EMP is intracranial EMP, which remains poorly understood due to the limited literature available on the subject. The objective was to comprehend the population characteristics, localization, type, treatment, and outcomes of intracranial EMP. A systematic review of the literature for EMPs was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The strategy "extramedullary plasmacytoma AND multiple myeloma" was used for the search. The search terms were queried using PubMed, Embase, Scopus, Cochrane, and Web of Science databases. We included only those studies that presented clinical studies with patients diagnosed with intracranial plasmacytomas. In this study, a total of 84 patients from 25 studies were analyzed. The average age of diagnosis was 57.25 years, with a slightly higher proportion of females (57%) compared to male patients (43%). The most common locations of intracranial plasmacytomas were the clivus (29.7%), frontal lobe (18.9%), parietal lobe (8.1%), occipital lobe (6.7%), temporal lobe (6.7%), and sphenoid (4%). Chordoma and meningioma were the most common differential diagnoses encountered during clinical investigations. Treatment modalities included radiotherapy (RT), chemotherapy (QT), surgical resection (SR), and conservative approaches. The most frequent treatment combinations were SR + RT (19%) and RT only (17.8%). Mortality was reported in 48% of the cases, with complete resolution observed in 10 cases and partial resolution in 3 cases. The average follow-up duration was 37.5 months. The clivus is the most frequently reported site of extramedullary intracranial plasmacytoma (EMIP) occurrence, representing 29.7% of cases. Chordomas were commonly observed alongside EMIPs and emerged as the primary differential diagnosis. RT was the predominant treatment modality, with SR considered when feasible. RT alone demonstrated the highest effectiveness in managing EMIPs (30%), while QT as a sole intervention showed lower efficacy. However, a combination of dexamethasone, lenalidomide, and targeted RT displayed promising results, offering improved tumor response and increased safety.

Extraosseous Plasmacytomas: A Radiologist's Perspective-A Narrative Review of the Literature.

Extraosseous plasmacytomas (EPs) are rare neoplasms originating from plasma cells, often associated with multiple myeloma. EPs are classified into three subtypes: extramedullary myeloma, solitary extramedullary plasmacytoma (SEP), and multiple solitary plasmacytomas. They can manifest in various anatomical sites, including the lung, mediastinum, breast, liver, pancreas, stomach, mesentery, kidney, small and large bowel, testis, and soft tissue. Despite their rarity, EPs present a diagnostic challenge due to their non-specific imaging appearances, which can mimic other neoplastic and inflammatory conditions. This review aims to describe the radiographic features of EPs in the chest, abdomen, and pelvis based on a thorough analysis of the existing literature. While imaging plays a crucial role in the detection and characterization of EPs, histological confirmation is necessary to differentiate them from other neoplastic entities. The review underscores the importance of considering EPs in the differential diagnosis, particularly in patients with a history of multiple myeloma. Understanding the imaging characteristics of EPs is essential for accurate diagnosis and appropriate management. Early imaging is crucial in these patients to exclude the possibility of EP, as timely diagnosis can significantly impact patient outcomes.

Solitary plasmacytoma of the pancreas: A rare case report.

A plasmacytoma is a cancerous growth of abnormal plasma cells that arise within osseous or soft tissue structures. In soft tissue structures, plasmacytomas can present as solitary or multiple masses in the absence of systemic involvement. Solitary plasmacytomas can be subcategorized as extramedullary plasmacytoma (derived from plasma cells located in soft tissues) or osseous plasmacytoma (derived from plasma cells located in the bone marrow). Infrequently, these tumors can arise as extramedullary lesions from the pancreas and present similarly to other tumors, such as pancreatic neuroendocrine tumors (PNETs). In this article, we report the case of a 62-year-old male with a diagnosis of solitary plasmacytoma of the pancreas. We focus on optimizing diagnosis and management through the application of radiological imaging modalities, specifically computed tomography (CT) scans and positron emission tomography-computed tomography (PET-CT) scans.

Recurrence of solitary plasmacytoma in the liver 10 years after the onset of multiple bone lesions.

A 79-year-old man presented with a history of solitary plasmacytoma in the bone 10 years ago. Chemoradiotherapy was effective, and remission was maintained with intermittent treatment at relapse of the bone lesions. One year after the last treatment, a follow-up computed tomography (CT) scan revealed multiple liver masses, and a liver biopsy revealed plasmacytoma. There was no clonal plasma cell infiltration in the bone marrow, and the final diagnosis was solitary plasmacytomas of the liver. Although liver involvement is known in relapsed refractory multiple myeloma, solitary plasmacytoma in the relapsed stage confined to the liver is rare, and all previous reports have been from the initial presentation. To the best of our knowledge, this is the first recurrent case of solitary plasmacytoma of the liver.

Enhanced clinical outcomes with radiotherapy in diagnostically challenging intracranial plasmacytomas: Analysis of 190 cases.

BACKGROUND: Intracranial plasmacytomas are rare tumors arising from plasma cells with approximately half of the cases progressing to multiple myeloma (MM). However, there is a lack of comprehensive clinical cohort analysis on the clinical and pathological features, progression, and outcomes of intracranial plasmacytomas. METHODS: A retrospective analysis of 190 cases was conducted, combining data from 38 cases in a single institution and 152 cases from the literature. Patient demographics, clinical presentations, tumor locations, imaging features, surgical treatments, and follow-up outcomes were collected and analyzed. Survival analysis and Cox regression analysis were performed to identify prognostic factors. RESULTS: A total of 190 intracranial plasmacytoma patients with an average age of 55.4 years were included in the study. The preoperative misdiagnosis ratio was high at 55.3%, and 59.7% of the tumors affected the calvaria convexity, compared to 40.3% located at the skull base. Resection and biopsy were achieved in 72.4% and 27.6% patients, respectively. Among them, 34.2% (65/190) of patients were initially diagnosed with MM with intracranial plasmacytoma as their first presentation (MM-IPFP), while 63.2% (120/190) of patients were diagnosed with solitary intracranial plasmacytoma (SIP), including 61 extramedullary plasmacytomas and 59 solitary bone plasmacytomas. In the SIP group, 22.4% (24/107) of patients experienced disease progression leading to the development of MM during a median follow-up time of 42.6 months (range 1-230 months). Multivariate analysis unveiled that radiotherapy (HR, 0.05; 95% CI, 0.00-0.87; p = 0.04), not surgery, was a protective prognostic factor for overall survival in MM-IPFP patients. Comparison between the SIP progression group and non-progression group revealed a significant difference of Ki-67 index (non-progression vs. SIP progression, 8.82% ± 7.03 vs. 16.5% ± 10.5, p < 0.05). AUC analysis determined that a cutoff value of 9.0% was the best predictor of SIP progression, with an area under the curve of 0.712. CONCLUSIONS: This retrospective clinical analysis highlights the potential role of radiotherapy, rather than surgical resection, in improving the outcomes of intracranial plasmacytoma. Additionally, the Ki-67 index is identified as a valuable marker for predicting disease progression. This would provide some evidence for the paradigm of diagnosis and treatment modalities for intracranial plasmacytomas from the large cohort.

Efficacy and Safety Analysis of VRD-PDCE in Treatment-Native Patients with Multiple Extramedullary Plasmacytomas or Plasma Cell Leukemia.

The prognosis of multiple extramedullary plasmacytomas (MEP) and plasma cell leukemia (PCL) is extremely poor, with the median overall survival (OS) of only 8 months with standard chemotherapy. Innovative treatment approaches incorporating various strategies are required to improve outcome. From November 2019 to September 2021, a total of 12 newly diagnosed MEP or PCL patients were enrolled in our department. An intensive chemotherapy treatment as VRD-PDCE consisted of bortezomib, lenalidomide, dexamethasone plus cisplatin, pegylated liposomal doxorubicin, cyclophosphamide and etoposide was first proposed. Disease activity and toxicity were evaluated after each cycle. Of the patients receiving therapy achieved a rapid and sustained response, and the overall response rate (ORR) was up to 75%. Nine patients achieved partial response (PR) or better, the response was the best response and the median time to best response was 4 cycles. Median overall survival (OS) and progression-free survival (PFS) were 24 (5-30) months and 18 (2-23) months. The toxicities were acceptable and there was no treatment related mortality. Our intensive treatment showed encouraging results in terms of disease control and improving survival, VRD-PDCE may be a novel regimen which is feasible and generally well-tolerated in MEP or PCL patients.

Unexpected Heterogeneity of Newly Diagnosed Multiple Myeloma Patients with Plasmacytomas.

In multiple myeloma (MM), malignant plasma cells infiltrate the bone marrow. In some cases, plasma cells migrate out of the bone marrow creating either para-skeletal plasmacytomas (PS) or infiltrating soft tissues as extramedullary plasmacytomas (EMD). The aim of this study was to define risk groups in newly diagnosed MM (NDMM) patients with PS and EMD plasmacytomas. In total, 523 NDMM patients with PS plasmacytomas and 196 NDMM patients with EMD plasmacytomas were diagnosed in the Czech Republic between 2004 and 2021 using modern imaging methods. Patients' data were analyzed from the Registry of Monoclonal Gammopathies of the Czech Myeloma Group. In NDMM patients with PS plasmacytomas, we found a subgroup with <5% of bone-marrow plasma cells to have the best prognosis (mPFS: 58.3 months (95% CI: 33.0−NA); mOS: not reached). The subgroup with >5% of bone-marrow plasma cells and ≥3 plasmacytomas had the worst prognosis (mPFS: 19.3 months (95% CI: 13.4−28.8), p < 0.001; mOS: 27.9 months (95% CI: 19.3−67.8), p < 0.001). Our results show association between tumor burden and prognosis of NDMM patients with plasmacytomas. In the case of PS plasmacytomas, NDMM patients with low BM PC infiltration have an excellent prognosis.

Real-World Evidence of Daratumumab Monotherapy in Relapsed/Refractory Multiple Myeloma Patients and Efficacy on Soft-Tissue Plasmacytomas.

INTRODUCTION: Daratumumab is an anti-CD38 agent that was first investigated as single agent in GEN501 and SIRIUS trials in patients with advanced multiple myeloma (MM). Overall response rate (ORR) was 30% with positive impact on progression-free survival (PFS). However, there is a lack of information regarding plasmacytoma response. MATERIALS AND METHODS: Here, we described a heavily pretreated group of 43 patients who received daratumumab monotherapy after EMA approval and focused on plasmacytoma response. RESULTS: After a median follow-up of 26 months, median time to best response was 2.9 months (range 0.8-13.1), median PFS was 5.2 months (95% CI 2.5 - 8.8) and median OS was 11.2 months (95% CI 6.3 - 17.0). Patients who achieved at least partial response had longer median PFS and OS (12.8 and 20.2 months, respectively) than those who achieved minimal response or stable disease (5.3 and 11.2 months, respectively). Ten patients (23%) had plasmacytomas (70% paraskeletal, 30% extramedullary). The clinical benefit for patients with and without plasmacytomas was 20% versus 42%. A dissociation between serological and plasmacytoma response was observed in 40% of the patients. Thus, 50% of the patients with plasmacytomas achieved at least serological minimal response but only 20% had plasmacytoma response. CONCLUSION: This is the first real-world study of daratumumab monotherapy that focuses on efficacy data regarding soft-tissue plasmacytomas in patients with relapsed/refractory mieloma, showing a limited benefit in this patient population.

Refractory multiple myeloma with extramedullary plasmacytoma of the spleen and suspicious teratoma: a rare case report and literature review.

Multiple myeloma (MM) is a type of malignant disease that is characterized by a clonal proliferation of plasma cells within the bone marrow. Relapsed and refractory multiple myeloma (RRMM) is a subtype of MM that is unreactive to salvage therapy and progresses during treatment or within 60 days of the last therapy in patients who achieved a minimal response before progression of disease. This usually results in a poor prognosis. Extramedullary plasmacytoma (EMP) occurs when MM occasionally develops in tissues other than bones marrow. To the best of our knowledge, case studies of the presence of EMPs in the spleen have rarely been reported. Teratoma is a type of congenital tumor that consists of tissue that arises from pluripotent embryonic cells. Here we report a case of refractory immunoglobulin G (IgG) MM with both splenic plasmacytomas and a suspicious teratoma. To investigate the clinical and treatment features of patients under similar conditions, we also reviewed the available literature supporting the useful information in the pathogenesis, diagnosis and treatment of RRMM with EMP.

Wwox Deletion in Mouse B Cells Leads to Genomic Instability, Neoplastic Transformation, and Monoclonal Gammopathies.

WWOX (WW domain containing oxidoreductase) expression loss is common in various cancers and characteristic of poor prognosis. Deletions, translocations, and loss of expression affecting the WWOX gene are a common feature of various B cell neoplasms such as certain B cell lymphomas and multiple myeloma. However, the role of this common abnormality in B cell tumor initiation and/or progression has not been defined. In this study, we conditionally deleted Wwox early in B cell development by means of breeding Cd19-Cre transgenic mice crossed to Wwox floxed mice (Cd19 Wwox KO). We observed a significant reduced survival in Cd19 Wwox KO mice and the development of B cell neoplasms including B cell lymphomas, plasma cell neoplasias characterized by increased numbers of CD138+ populations as well as monoclonal gammopathies detected by serum protein electrophoresis. To investigate whether Wwox loss could play a role in genomic instability, we analyzed DNA repair functions during immunoglobulin class switch joining between DNA segments in antibody genes. While class switch recombination (CSR) was only slightly impaired, Wwox deficiency resulted in a dramatic shift of double strand break (DSB) repair from normal classical-NHEJ toward the microhomology-mediated alternative-NHEJ pathway, a pathway associated with chromosome translocations and genome instability. Consistent with this, Wwox deficiency resulted in a marked increase of spontaneous translocations during CSR. This work defines for the first time a role for Wwox for maintaining B cell genome stability during a process that can promote neoplastic transformation and monoclonal gammopathies.

Distinct Clinical Outcomes between Paramedullary and Extramedullary Lesions in Newly Diagnosed Multiple Myeloma.

This retrospective study aimed to compare the clinical features of paramedullary lesions (PLs) and extramedullary lesions (ELs) of plasmacytomas at diagnosis, using positron emission tomography integrated with computed tomography, using glucose labeled with the positron-emitting radionuclide 18F (18F-FDG-PET/CT) in newly diagnosed multiple myeloma (NDMM), and to address their prognostic impact. Sixty-four patients with NDMM presenting ELs (n=22) and/or PLs (n=42) were included. Patients with ELs at initial presentation had unfavorable laboratory parameters of calcium and lactate dehydrogenase, a higher percentage of bone marrow plasma cells, and showed a trend toward advanced international staging system (ISS), compared to patients with PLs. Using X-ray imaging, high bone disease (HBD) was observed in 50% and 71% of patients with ELs and PLs, respectively. After a median follow-up of 29.2 months (range, 3.4-76.5 months) in survivors, patients with ELs had a significantly lower overall survival (OS) (p=0.033) than patients with PLs did, whereas the progression-free survival (PFS) did not differ significantly (p=0.818). However, the PFS after 1st progression was significantly worse in patients with ELs than in those with PLs (p=0.017). In the multivariate analyses, the negative impact of initial ELs on OS (p=0.033) was sustained. Our results demonstrated the different clinical features and outcomes of ELs and PLs in NDMM. Patients with initial ELs showed a shorter PFS after 1st progression, which translated into poor OS, providing insight into the different biological effect of ELs.

Leukemia Cutis Associated with Secondary Plasma Cell Leukemia.

Plasma cell leukemia is an uncommon, aggressive variant of leukemia that may occur de novo or in association with multiple myeloma. Leukemia cutis is the cutaneous manifestation of leukemia, and indicates an infiltration of the skin by malignant leukocytes or their precursors. Plasma cell leukemia cutis is a rare clinical presentation of leukemia. We present a man who developed plasma cell leukemia cutis in association with multiple myeloma. Cutaneous nodules developed on his arms and legs 50 days following an autologous stem cell transplant. Histopathologic examination showed CD138-positive nodular aggregates of atypical plasma cells with kappa light chain restriction, similar to the phenotype of his myeloma. In spite of systemic treatment of his underlying disease, he died 25 days after the presentation of leukemia cutis. Pub-Med was searched for the following terms: cutaneous plasmacytomas, leukemia cutis, plasma cell leukemia nodules, plasma cell leukemia cutis, and secondary cutaneous plasmacytoma. Papers were reviewed and appropriate references evaluated. Leukemia cutis in plasma cell leukemia patients is an infrequent occurrence. New skin lesions in patients with plasma cell leukemia should be biopsied for pathology and for tissue cultures to evaluate for cancer or infection, respectively. The diagnosis plasma cell leukemia cutis is associated with a very poor prognosis.

Solitary extraosseous plasmacytoma.

Plasma cell neoplasms are characterized by a neoplastic plasma cell lineage which produces a monoclonal immunoglobulin. These neoplasms can present as a single lesion (solitary plasmacytoma) or as multiple lesions (multiple myeloma). Solitary plasmacytomas most frequently occur in bone (plasmacytomas of bone), but can also be found outside bone in soft tissues (extramedullary plasmacytomas).

Successful treatment of a gastric plasmacytoma using a combination of endoscopic submucosal dissection and oral thalidomide.

We report a rare case of a gastric plasmacytoma treated with endoscopic resection and oral thalidomide therapy. A 70-year-old man was admitted to our hospital with indigestion. He had no specific medical history and unremarkable laboratory results. Gastroendoscopic findings revealed a focal, erythematous, flat elevated lesion in the anterior wall of the stomach antrum. A biopsy revealed atypical lymphocytes. Endoscopic submucosal dissection (ESD) with an insulation-tipped knife was performed 45 days after diagnosis. Radiological and hematological evaluations, including a bone marrow biopsy, were performed and showed no involvement of other organs. The patient was diagnosed with extramedullary gastric plasmacytoma. Follow-up gastroendoscopy was performed three times during a 2-year period and showed nonspecific ESD scarring. The patient's condition was found to be stable.