Primary Ewing sarcoma of the kidney mimicking cystic papillary renal cell carcinoma in an older patient:A case repor

BACKGROUND Ewing’s sarcoma(ES)is a neuroectodermal tumor that typically occurs in the bones and soft tissues of children and young adults.Primary renal ES is rare;only a few cases and a small case series have been documented,and only four cases involved primary renal ES in older people(>65 years old).CASE SUMMARY Herein,we describe the radiological and pathological features of primary renal ES in an older person.A 76-year-old man complained of poor oral intake and was found to have a large cystic renal mass with indistinct margins on computed tomography.Ultrasound-guided biopsy revealed that the tumor contained small round blue cells.The patient underwent a right radical nephrectomy.The tumor cells showed diffuse membranous CD99,and nuclear friend leukemia integration 1 transcription factor and NK2 Homeobox 2.Fluorescence in situ hybridization revealed EWSR1 translocation.Postoperatively,18F-fluorodeoxyglucose positron emission tomography revealed no evidence of metastasis.The patient was diagnosed with primary renal ES.Six months following the surgery,local recurrence and distant metastasis were observed.Primary renal ES is rare and often lethal in older individuals.The specific imaging findings are unknown,and treatment protocols have not been standardized.CONCLUSION This case report describes the radiological and pathological features of primary renal ES in an older person.