Prostate cancer initially misdiagnosed as prostatic abscess in a 36-year-old kidney transplant recipient

Renal transplant recipients (RTRs) have a 2-4 fold increased risk of malignancy due to long-term immunosuppression. We report a diagnostically challenging case of a 36-year-old man with a 16-year history of renal transplantation who presented with perineal pain, fever, and rising prostate-specific antigen (PSA), initially diagnosed as prostatic abscess. Ultrasound-guided aspiration yielded bloody rather than purulent fluid, prompting immediate biopsy that revealed poorly differentiated, PSA-negative prostate adenocarcinoma with BRCA2, ATM, and TP53 mutations. He underwent 3D laparoscopic radical prostatectomy with a modified surgical approach to avoid the transplant kidney. Postoperative genomics revealed multiple DNA damage repair gene mutations, raising therapeutic dilemmas regarding PARP inhibitor use in transplant recipients due to drug interactions with tacrolimus and potential nephrotoxicity. At 1-year follow-up, PSA was undetectable and graft function stable. This case highlights that in RTRs with pelvic symptoms, bloody aspirate from a presumed abscess should prompt immediate tissue biopsy, and rising PSA trajectory warrants investigation even in the "gray zone."