Supplementary Material for: A RARE PRESENTATION OF EXTRAMEDULLARY PLASMACYTOMA: A CASE REPORT

INTRODUCTION: Extramedullary plasmacytoma is a rare manifestation of monoclonal plasma cell disorders, typically involving the upper aerodigestive tract. Gastrointestinal involvement is uncommon, and synchronous lesions in separate GI sites are particularly rare. CASE REPORT: A 58-year-old male was referred to the Gastroenterology department following the incidental identification of two subepithelial lesions, measuring 10 mm and 15 mm in the transverse and descending colon, respectively, during routine screening colonoscopy. A subsequent hospital-based colonoscopy confirmed these lesions and revealed additional nodular subepithelial lesions in the terminal ileum. Endoscopic biopsies were inconclusive. One colonic and one ileal lesion were removed via endoscopic mucosal resection. Histopathological and immunohistochemical analysis confirmed IgG-kappa extramedullary plasmacytomas. Further hematological evaluation revealed no cytopenias, renal dysfunction, or hypercalcemia. Skeletal survey was unremarkable, and bone marrow biopsy showed phenotypically normal plasma cells. Given the multifocal gastrointestinal involvement, systemic therapy with bortezomib, dexamethasone, and lenalidomide was initiated, and the patient was referred for autologous stem cell transplantation. CONCLUSION: This case involves a rare entity with an exceptionally uncommon presentation—multifocal gastrointestinal plasmacytomas—posing unique diagnostic and therapeutic challenges that require a multidisciplinary approach. Early recognition is crucial, given the risk of progression to multiple myeloma and the need for timely, effective intervention.引言：髓外浆细胞瘤（Extramedullary plasmacytoma）是单克隆浆细胞疾病（monoclonal plasma cell disorders）的罕见临床表现形式，通常累及上呼吸消化道（upper aerodigestive tract）。胃肠道受累（gastrointestinal involvement）较为少见，而在不同胃肠道部位出现同步性病变（synchronous lesions）的情况更是尤为罕见。 病例报告：一名58岁男性因在常规筛查结肠镜检查中偶然发现两处上皮下病变（subepithelial lesions）（分别位于横结肠、降结肠，大小为10mm与15mm），被转诊至消化内科。后续院内结肠镜检查确认了上述病变，并在末端回肠（terminal ileum）发现额外的结节状上皮下病变。内镜活检（endoscopic biopsies）结果无明确诊断意义。通过内镜黏膜切除术（endoscopic mucosal resection）切除了一处结肠病变与一处回肠病变。组织病理学与免疫组化分析（histopathological and immunohistochemical analysis）证实为IgGκ型（IgG-kappa）髓外浆细胞瘤。进一步血液学评估未发现血细胞减少症（cytopenias）、肾功能不全（renal dysfunction）或高钙血症（hypercalcemia）。骨骼影像学检查（skeletal survey）无异常发现，骨髓活检（bone marrow biopsy）显示浆细胞表型正常。鉴于存在多灶性胃肠道受累，遂启动硼替佐米（bortezomib）、地塞米松（dexamethasone）联合来那度胺（lenalidomide）的全身治疗（systemic therapy），并将患者转诊至自体干细胞移植（autologous stem cell transplantation）流程。 结论：本病例涉及一种罕见病症，其表现形式极为特殊——多灶性胃肠道浆细胞瘤，该病症带来了独特的诊断与治疗挑战，需采用多学科协作诊疗模式。鉴于存在进展为多发性骨髓瘤（multiple myeloma）的风险，且需要及时开展有效干预，早期识别至关重要。