Cystic formations in the prostate are quite common, but the vast majority are benign. The cystic form of prostate adenocarcinoma can present unexpected symptoms, and management can be difficult because of the local advanced stage of the disease. A unique feature of this case is the surgical local cancer treatment. In this clinical case, we describe the literature surrounding this rare form of neoplasm. We present a clinical case of a rare form of prostate cancer in a 71-year-old male who was admitted to ER with acute urinary retention. A huge obstructing prostatic cyst was revealed. After successful trial-without-catheter, the patient underwent transperineal cyst draining and this restored urination. PSAt was increased up to 55 ng/mL. The cystic wall biopsy revealed adenocarcinoma with a Gleason score of 8 (4+4) (Gleason Group IV), and distant metastasis was noticed with PSMA PET/CT. The patient started androgen deprivation therapy (ADT) with excellent PSA dynamics in three months. Because of lower urinary tract symptoms, he needed local treatment and underwent radical prostatectomy. A three-month follow-up demonstrated a common post-operative period, mild stress incontinence, and PSAt 0.004 ng/mL. Cystic prostatic carcinoma can manifest as urinary retention and be mistakenly taken for a benign obstructing prostate cyst. Despite the locally advanced tumor, it can be successfully treated locally in highly selected patients.