Introduction. Ewing's extraosseous sarcoma of the genitourinary system is an extremely rare disease. There are sporadic publications about the genitourinary sarcomas.
We present a case of a primitive neuroectodermal pelvic tumor with bladder invasion in a 58-year-old man. Initially, he was admitted with complaints of intense lower abdominal and right lumbar pain, severe dysuria, macrohematuria, weight loss (by 15 kg in 6 months) and general weakness. Previously, a nephrostomy tube was put due the right hydronephrosis. Nephrostomy output was up to 100-150 ml per day, and glomerular filtration rate was estimated within 5 ml/min. According to MRI data, the extra-organ pelvis tumor with bladder invasion along the right posterolateral wall was diagnosed. Cystoprostatectomy, right nephroureterectomy and left ureterocutaneostomy were performed. In the postoperative period, the patient firstly manifested neurological symptoms (paresis). According to the brain CT, two lesions of the right frontal and left parietal regions were found (most likely metastases of the primary tumor). Late admission and disseminated tumor with local invasion and brain metastases, right terminal hydronephrosis, anemia due to pronounced macrohematuria and decrease of the body weight determined an unfavorable outcome.
Conclusions. Our case report allows us to remind urologists about the presence of orphan oncological diseases with an extremely aggressive course. In-depth diagnosis requires the use of immunohistochemical methods, and the treatment of such patients should be based on a multidisciplinary approach.

Keywords: extra-organ pelvis sarcoma, primitive neuroectodermal pelvic tumor of genitourinary system, PNET