A Caucasian man 84 years old was admitted to our Department for acute renal failure secondary to severe bilateral hydronephrosis; moreover, the patient referred chronic fatigue and was anuric from two days. Serum creatinine and PSA values were equal to 9.6 mg/dl and 4.8 ng/ml and digital rectal examination was highly suspicious for prostate cancer. In emergency, the patient underwent bilateral application of percutaneous renal nephrostomies to restore kidney function and, after three days, was submitted to ultrasound-guided extended transperineal biopsy; the histology showed the presence of a prostatic small cell carcinoma (SCC) fulfilling the World Health Organization criteria. The patient underwent clinical staging including chest and abdominal computed tomography evaluation and total body scan that did not demonstrated distant metastases and/or others primitive tumors; in addition, cystoscopy and urinary cytology were negative. The patient underwent multidisciplinary evaluation, but he died 20 days from the diagnosis for progressive clinical worsening (physical and cognitive impairments) before beginning oncological treatment. In conclusion, primitive SCC represents a very rare cancer provided of poor prognosis; only the execution of prostate biopsy combined with an accurate specimen analysis allow to make the correct diagnosis and therapeutic treatment.