Supplementary Material for: Clinicopathologic Characteristics of Intraglomerular Malignancy in Kidney Biopsies

Introduction: Intraglomerular malignancy (IGM) is a rare finding with current data limited to case reports and small, often postmortem, series. This study aims to characterize the clinicopathologic features of kidney biopsy cases with IGM.

Methods: Renal biopsy cases diagnosed with IGM from January 2000 to June 2023 at Cedars-Sinai Medical Center were retrospectively reviewed. Demographic, clinical characteristics, and pathologic data were collected, and cases were divided into hematologic (HEME) versus non-hematologic (non-HEME) malignancy.

Results: We identified 9 patients with IGM. 5 were hematolymphoid in origin and 4 were from metastatic solid tumor (2 carcinomas from the lung, 1 neuroendocrine tumor of likely lung origin, and 1 from the head and neck). All patients presented with proteinuria and hematuria, and 89% had renal dysfunction. The median serum creatinine was 2.9 (IQR 1.7-5.7) mg/dL. All non-HEME patients had an established malignant diagnosis at the time of kidney biopsy, whereas all HEME cases were initially or concurrently diagnosed at the time of biopsy. Two of the non-HEME biopsies showed extracapillary hypercellularity due to malignant cells, a feature not seen in HEME cases. Of the 8 patients with follow-up available, 7 (88%) died within a median of 69 (IQR 4-161) days.

Discussion/Conclusion: IGM is a rare presentation of disseminated malignancy, often indicating advanced disease with poor prognosis. Nephropathologists should be aware of IGM as a histologic mimicker of endocapillary hypercellularity or cellular crescent formation. Similarly, the provision of complete clinical history is critical for accurate biopsy assessment and to avoid this diagnostic pitfall. Given its high mortality rate and the short interval between tissue diagnosis and death, the identification of IGM should prompt urgent medical attention.

Introduction: 肾小球内恶性病变（intraglomerular malignancy, IGM）是一种罕见的病理表现，目前相关研究数据仅局限于个案报告以及小型（多为死后）系列病例研究。本研究旨在明确伴IGM的肾活检病例的临床病理特征。
Methods: 本研究对2000年1月至2023年6月期间，于锡达斯-西奈医疗中心确诊为IGM的肾活检病例进行了回顾性分析。收集所有病例的人口学、临床特征及病理资料，并将其分为血液系统恶性病变组（hematologic, HEME）与非血液系统恶性病变组（non-hematologic, non-HEME）。
Results: 本研究共纳入9例IGM患者，其中5例为血液淋巴系统来源恶性病变，4例为转移性实体瘤（2例为肺癌，1例为疑似肺来源的神经内分泌肿瘤，1例为头颈部来源肿瘤）。所有患者均表现为蛋白尿与血尿，89%的患者存在肾功能不全。中位血清肌酐值为2.9（四分位距1.7~5.7）mg/dL。所有非HEME组患者在接受肾活检前已明确恶性肿瘤诊断，而所有HEME组患者均在肾活检时首次确诊或同期确诊恶性肿瘤。4例非HEME组患者的肾活检标本中，有2例可见恶性细胞导致的毛细血管外细胞增生，该表现在HEME组中未出现。在获得随访资料的8例患者中，7例（88%）在确诊后中位69天（四分位距4~161天）内死亡。
Discussion/Conclusion: IGM是播散性恶性肿瘤的罕见临床表现，通常提示疾病已进展至晚期且预后不良。肾脏病理医师应注意到IGM可作为一种组织学模拟物，模仿毛细血管内细胞增生或细胞性新月体形成的表现。同样，提供完整的临床病史对于准确评估肾活检标本、避免此类诊断陷阱至关重要。鉴于该病变的高死亡率，以及组织学确诊至死亡的间隔时间较短，一旦发现IGM应立即给予紧急医疗干预。