Primary renal Ewing's sarcoma (ES) is extremely rare, and only two cases causing Cushing's syndrome (CS) have been reported to date. We report that the case of an 18-year-old patient is diagnosed primary renal ES with typical CS characterized by purple stripes, weight gain, and hypertension.

CS was first diagnosed by laboratory testing. A huge tumor was revealed in the kidney following an imaging examination. Moreover, brain and bone metastases were observed. After comprehensive treatment, primarily based on surgery, primary renal ES was pathologically diagnosed with a typical EWSR1-FLI1 genetic mutation through genetic testing. Furthermore, the glucocorticoid level returned to normal. By the ninth postoperative month of follow-up, the patient was recovering well. Cushing-related symptoms had improved, and a satisfactory curative effect was achieved.

Primary renal ES, a rare adult malignant tumor, can cause CS and a poor prognosis.

To present the clinical experience of primary renal Ewing's sarcoma/primitive neuroectodermal tumors (rEWs/PNET) admitted to our hospital and systematically review the published literature. A retrospective analysis was performed on patients with pathologically confirmed renal EWs/PNET (rEWs) in our hospital, and the literature on rEWs published in PubMed and Embase databases before March 1, 2022 was searched for analysis. A total of 337 rEWs were included in the statistical analysis, including 6 cases of our patients and 331 cases published in the literature. The common clinical symptoms of rEWs are abdominal pain, hematuria, abdominal mass and so on. computed tomography (CT) plays an important role in the diagnosis of rEWs, and the typical manifestation is a large heterogeneous soft tissue density mass, with a specific "septum-like" enhancement in contrast-enhanced scan. The 2-year overall survival rate of rEWs was 48%, with a median survival time of 18 months. "Septum-like" enhancement on CT can be used as a relatively specific sign for the differential diagnosis of rEWs from Wilms tumor and neuroblastoma. The maximum diameter of the rEWs was usually greater than 10 cm, the clinical symptoms of weight loss, metastasis at diagnosis, tumor thrombogenesis of renal vein or/and inferior vena cava tumor, and the failure to undergo radical nephrectomy were the factors of poor prognosis. The incidence of primary rEWs is low and the prognosis is poor. Early diagnosis and radical nephrectomy combined with chemotherapy is the key to improve the prognosis of patients, and CT plays an important role in early diagnosis.

Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET) of the kidney in children younger than 10 years of age is extremely rare. We describe here the case of a 7-year-old female patient who was diagnosed with ES/PNET. The timeframe for this case spanned from 8 months prior to diagnosis until 8 months postsurgical removal of the tumor. In addition, we summarized the cases of PNET in children younger than 10 years of age in the last decade.