[A Case of Rectum-Infiltrating Prostate Cancer Mimicking Prostate-Infiltrating Rectal Cancer]

Area of Science:

• Oncology
• Urology
• Gastroenterology

Background:

• Prostate cancer rarely invades the rectum due to the protective Denonvillier's fascia.
• Distinguishing between rectal cancer invading the prostate and prostate cancer invading the rectum can be diagnostically challenging.

Observation:

• A 71-year-old male presented with constipation, found to have rectal stenosis.
• Initial diagnosis suggested rectal adenocarcinoma infiltrating the prostate after endoscopic biopsy and imaging.
• Post-neoadjuvant therapy, surgical pathology revealed prostate cancer infiltrating the rectum.

Findings:

• The final pathological diagnosis confirmed prostate cancer infiltrating the rectum, contrary to the initial assessment.
• This underscores the diagnostic difficulty in differentiating reciprocal invasion between these two organs.

Implications:

• When rectal cancer invading the prostate is suspected, consider prostate cancer infiltrating the rectum.
• Measuring serum prostate-specific antigen (PSA) levels and performing PSA immunostaining are vital for accurate diagnosis.
• This case emphasizes the importance of a high index of suspicion and appropriate diagnostic workup for rare oncological presentations.