Case Report: Prostate adenocarcinoma with peritoneal carcinomatosis and elevated CEA mimicking colorectal cancer: a diagnostic dilemma.

A 65-year-old man with localized high-grade prostate adenocarcinoma (Gleason 4 + 4) underwent robotic prostatectomy in November 2020, followed by salvage radiation and stereotactic body radiation therapy for early biochemical recurrence.

He achieved an excellent response to androgen deprivation therapy (androgen deprivation therapy) combined with abiraterone and prednisone, maintaining an undetectable prostate-specific antigen (prostate-specific antigen) level for over 2 years.

In late 2024, the patient developed hematochezia, narrow stools, and abdominal pain.