Urinary cytologic features of primitive neuroectodermal tumor primarily involving the kidney: A case report.

Renal primitive neuroectodermal tumor(rPNET) is an extremely rare and distinct entity that can be mistaken for a variety of other round cell tumors. Findings from fine needle aspiration cytology have been reported, but there have been no reports of PNET cytomorphological features in urine cytology specimen. Here, we report a case of PNET characterized by urine cytology. A 24-year-old girl presented with hematuria for half a month. Computed tomography showed a large tumor involving the upper pole of the right kidney. Urinary cytology exhibited highly cellular clusters composed of small, round, atypical cells with little cytoplasm and a high nuclear/cytoplasmic ratio. Following a right nephrectomy, the biopsy confirmed the diagnosis of rPNET. Additionally, immunohistochemistry (IHC) staining of the decolorized liquid-based cytology slide was positive for CD99, further confirming the diagnosis through urine cytology. Our observations suggest that urinary cytology in combination with cytological morphology and immunocytochemistry may be a potentially useful method for the detection of PNET.