Ewing sarcoma/primitive neuro-ectodermal tumor of the urogenital system in children: a retrospective observational case series.

Introduction: Pediatric Ewing sarcoma (ES)/primitive neuro-ectodermal tumor (PNET) occurring in the genitourinary system has been rarely reported. And the result of long-term follow-up is still a matter of debate.

Objective: The aim of the study was to identify the characteristics, therapeutic strategies, and long-term outcomes of pediatric ES/PNET in the genitourinary system.

Patients And Methods: All children with genitourinary system PNET from a single center were retrospectively reviewed. The American Joint Committee on Cancer (AJCC) staging system was used to evaluate tumor grade.

Results: Four patients were included. Three were boys, and 1 was a girl. The locations of the lesions were the penis in 1 patient, ureter in 1 patient, and kidney in 2 patients. Two patients were of AJCC stage IVB, and the other 2 patients were of stage IIA. In the follow-up ranging from 2.5 to 8.0 years, 3 patients had survival, and 1 patient died. The patient with penis PNET survived during the 8 years of follow-up. One patient with renal PNET had tumor thromboses in the renal vein, inferior vena cava, and right atrium, which was the first definite report in children (case 3).

Discussion: Primitive neuro-ectodermal tumor as a highly malignant subgroup of blue round cell tumor is extremely rare in the genitourinary system, especially in children. The current case series represents the first report of penis PNET in children with the longest (8 years) follow-up and first definite report of pediatric renal PNET with vena cava and atrium tumor thrombus. In contrast to the previous literature, the patient with ureteral PNET in this study was much younger, who was the youngest child to be reported in the literature thus far. Although the key prognostic factor of the outcomes is detectable metastases at diagnosis, the patient with penis PNET and bone and lung metastasis in this series still survived. It was hypothesized from the data of present cases that young age was a protective factor, which was consistent with the previous literature. Aggressive therapy is not trivial for patients with multiple recurrences who can also be a long-term survivor. The survival outcomes of these high-stage patients were favorable with combination treatment. As the patient with penis PNET in this series had bone metastasis at his 7.5 years after definite diagnosis, five years of follow-up was not enough. The follow-up period should be extended, even to a lifetime follow-up.

Conclusions: Children with PNET have a better prognosis than adults. Aggressive combination treatment should be performed to improve prognosis and the survival rate. It is better to monitor the changes of the disease by extending the follow-up period.