Fatal lymphatic-dominant progression in metastatic prostate cancer initially presenting with a clinically suspected inguinal node metastasis: a case report.

Prostate cancer presenting with a clinically suspected inguinal lymph node metastasis (ILNM) is an exceptionally rare and aggressive disease variant. We report a case of a patient with metastatic hormone-sensitive prostate cancer (mHSPC) who presented with an isolated inguinal mass and subsequently developed fatal lymphatic-dominant progression despite standard intensive systemic therapy and an initial deep PSA response. A 68-year-old male patient presented with a painless right groin mass. Imaging and biopsy confirmed high-volume mHSPC (PSA 776.0 ng/mL, Gleason score 8) with suspected inguinal, pelvic, and bone metastases. Treatment with androgen deprivation therapy (ADT) and abiraterone acetate was initiated, achieving a PSA nadir of <0.090 ng/mL. Approximately nine months later, he developed refractory lower limb and scrotal edema, bilateral hydronephrosis, and renal impairment. Despite comprehensive supportive care including ureteral stenting, his condition deteriorated rapidly, resulting in death. This case highlights a rare clinical scenario of lymphatic-dominant progression occurring despite excellent systemic biochemical control. It underscores the need for vigilant monitoring of regional lymphatic complications and early multidisciplinary intervention in high-risk mHSPC patients presenting with non-typical metastases.