Metastatic disease in the kidney is relatively uncommon compared to other body sites. In most cases it presents as a unilateral and unifocal mass in the tubulointerstitial region. Intraglomerular metastases are even rarer, and their diagnosis is hampered by the limitations of imaging techniques in detecting them. We describe the finding of intraglomerular metastases in a patient affected by a malignant melanoma considered to be in partial remission, with no evidence of melanoma progression on the previously performed computed tomography scan. This patient developed rapidly progressive kidney failure, proteinuria, and hematuria with dysmorphic red blood cells in the urine sediment. Kidney biopsy showed a marked crescentic proliferation caused by tumor cells, which even invaded the proximal convoluted tubule. Melanoma cells were also found in the lumina of the glomerular capillaries, distending their basement membranes. Our case describes the histologic and electron microscopic findings of this form of intraglomerular metastasis and reminds us of its inclusion in the differential diagnosis of rapidly progressive kidney failure.

与其他身体部位相比，肾脏的转移性疾病相对少见。在大多数情况下，它表现为肾小管间质区域的单侧和单焦点肿块。肾小球内转移甚至更罕见，并且它们的诊断受到成像技术检测它们的限制的阻碍。我们描述了在一名被认为处于部分缓解状态的恶性黑色素瘤患者中发现肾小球内转移，在先前进行的计算机断层扫描中没有黑色素瘤进展的证据。该患者出现快速进行性肾功能衰竭、蛋白尿和血尿，尿沉渣中有畸形红细胞。肾活检显示肿瘤细胞引起明显的新月体增生，甚至侵犯近曲小管。在肾小球毛细血管的管腔中也发现了黑色素瘤细胞，使它们的基底膜膨胀。我们的病例描述了这种形式的肾小球内转移的组织学和电镜检查结果，并提醒我们将其纳入快速进展性肾衰竭的鉴别诊断中。