[Eosinophilic vacuolated tumor of the kidney: clinicopathological and molecular characteristics].

Objective: To study the clinicopathological features, immunophenotype, molecular changes, differential diagnosis and prognosis of eosinophilic vacuolated tumor (EVT) of the kidney. Methods: Four cases were collected retrospectively from 2014 to 2020 at Ningbo Diagnostic Pathology Center. The clinicopathologic features and immunophenotypic profile were studied by light microscopy and immunohistochemistry. Targeted next-generation sequencing (NGS) panel was used to detect cancer-associated mutation. Follow-up and literature review were also performed. Results: Among the 4 patients studied,2 were males and 2 were females. The age of the patients ranged from 44 to 63 years (the mean age: 51 years).Tumor size ranged from 1.5 to 4.2 cm (mean: 2.3 cm). Microscopically, tumors were well-circumscribed, unencapsulated. Thick-walled vessels and entrapped renal tubules were found within or at the periphery of the tumors. The tumors were predominantly composed of nest pattern, and focal tubular pattern. The tumor cells exhibited abundant, eosinophilic, granular cytoplasm and conspicuous, large nucleoli. Prominent intracytoplasmic vacuoles were seen. These cytoplasmic vacuoles varied in size and frequently coalesced into a large space. Loose fibromatous or hyaline stroma was focally noted. Immunohistochemically, the tumor cells in all cases exhibited a CD117+/CK7-phenotype. All cases were positive for CD10 and p504s. MTOR, S6 and cathepsin K were positive in 4 cases. TFE3, CA9, Melan A and HMB45 were negative in all cases. SDHB retained expression. NGS demonstrated MTOR mutations in all cases, and TSC2 mutation in 2 cases. Conclusions: EVT is a rarely oncocytic renal tumor with unique morphology, immunohistochemical phenotype, molecular profile and an indolent behavior. Recognition of the characteristics of this novel but rare entity will allow for better classification of renal tumors.目的： 探讨嗜酸性空泡状肾肿瘤（eosinophilic vacuolated tumor of the kidney，EVT）的临床病理特征、免疫表型、分子改变、鉴别诊断及预后。 方法： 回顾性收集宁波市临床病理诊断中心2014至2020年间的4例EVT的临床病理学资料，进行光镜观察、免疫组织化学染色、高通量DNA靶向测序及随访，并复习相关文献。 结果： 4例患者，其中女性2例，男性2例。患者年龄44~63岁，平均年龄51岁。肿块最大径1.5~4.2 cm（平均肿块最大径2.3 cm）。镜下肿瘤境界清楚、无包膜，肿瘤内及周围可见厚壁血管，肿瘤细胞主要呈巢状结构、少量管状结构，肿瘤细胞胞质丰富嗜酸、颗粒状，一个显著的特征是存在明显的、大小不一的胞质空泡（通常为大的细胞质空泡）、核仁明显，局部间质疏松水肿或透明变。免疫表型：4例EVT均弥漫表达CD117，细胞角蛋白（CK）7均阴性，CD10和P504s均阳性，4例MTOR、S6和Cathepsin K均阳性，TFE3、碳酸酐酶9、Melan A和HMB45均阴性，SDHB阳性表达。高通量DNA靶向测序证实4例病例均存在MTOR基因突变，其中2例同时存在TSC2基因突变。平均随访46个月，均无病生存。 结论： EVT是一种罕见的嗜酸细胞性肾肿瘤，具有独特的形态、免疫组织化学和分子特征，生物学行为惰性，识别这种新的罕见的具有独特特征的实体将更好的分类肾肿瘤。.