Clear cytoplasm is a major characteristic feature of most malignant renal neoplasms. Benign clear cells in the renal parenchyma, usually histiocytes, can occasionally be found, but they are infrequently of an epithelial nature. We report histological, immunohistochemical, ultrastructural, and cytogenomic features of clear epithelial cell clusters incidentally found in four kidney specimens. Multiple microscopic clear cell clusters were present in the cortex, often in subcapsular location. They were composed of large epithelial cells with strikingly clear cytoplasm, without nuclear atypia, arranged in solid nests, and some tubules with narrow lumina. Immunohistochemically, they were positive for AE1AE3, PAX 8, EMA, kidney-specific cadherin, cytokeratin 7, E cadherin, and CD117, with focal immunoreactivity for CD10. Carbonic anhydrase IX, vimentin, and markers related to apoptosis and proliferation were negative. Ultrastructurally, the cytoplasms were enlarged and poor in organelles, showing ballooning degeneration. Array comparative genomic hybridization showed no chromosomal gains or losses. Clear cell clusters constitute a rare finding in the kidney and must be differentiated from benign lesions (ectopic adrenal tissue, osmotic tubulopathy, histiocytic clusters, renal adenomas) and renal cell carcinomas. Clear cell clusters appear to be generated from “endocrine-type” atrophic tubules whose cells are enlarged due to intracellular oedema. Immunohistochemistry shows a distal nephron phenotype with a limited expression of a proximal marker, CD10. Coexisting chronic renal disease or ischemic conditions seem to be related to the development of clear cell clusters. Pathological, ultrastructural, and cytogenomic features do not support a preneoplastic nature of this lesion, at least in the cases studied here.

透明的细胞质是大多数恶性肾肿瘤的主要特征。肾实质中的良性透明细胞，通常是组织细胞，偶尔可以发现，但它们很少具有上皮性质。我们报告了在四个肾脏标本中偶然发现的透明上皮细胞簇的组织学、免疫组织化学、超微结构和细胞基因组学特征。皮层中存在多个微观透明细胞簇，通常位于包膜下位置。它们由大的上皮细胞组成，细胞质非常清晰，无异型核，排列成实心巢状，部分小管内腔狭窄。免疫组织化学上，它们对 AE1AE3、PAX 8、EMA、肾特异性钙粘蛋白、细胞角蛋白 7、E 钙粘蛋白和 CD117 呈阳性，对 CD10 具有局灶性免疫反应性。碳酸酐酶 IX、波形蛋白、与细胞凋亡和增殖相关的标志物均为阴性。超微结构上，细胞质增大，细胞器贫乏，呈气球样变性。阵列比较基因组杂交显示没有染色体增益或丢失。透明细胞簇在肾脏中是一种罕见的发现，必须与良性病变（异位肾上腺组织、渗透性小管病变、组织细胞簇、肾腺瘤）和肾细胞癌相鉴别。透明的细胞簇似乎是由“内分泌型”萎缩性小管产生的，这些小管的细胞因细胞内水肿而扩大。免疫组织化学显示远端肾单位表型，近端标志物 CD10 表达有限。并存的慢性肾病或缺血性疾病似乎与透明细胞簇的形成有关。病理，