Prostate cancer solitary metastasis to anal canal: case report and review of literature

BACKGROUND: Here we present the first cases of prostate cancer solitary metastasis to anal canal. CASE PRESENTATION: A 67-year-old male patient underwent radical prostatectomy with ilio-obturator lymphonodectomy in 2016 due to poorly differentiated ductal adenocarcinoma (Gleason 4 + 5(40%) = 9) pT3bN0. Two months later increasing PSA rate was noted and the patient started adjuvant intermittent androgen deprivation therapy combined with radiotherapy. Year after patient was admitted to the hospital complaining of dyschezia, pain in anal canal, and bloody stool. Digital rectal examination revealed an anal fissure with ulceration. A biopsy from ulcerated area showed poorly differentiated ductal adenocarcinoma of the prostate. Because there was no evidence of distant metastases on abdominal computed tomography (CT) scan and pelvic magnetic nuclear resonance imaging (MRI) and the only metastasis was in anal canal patient underwent laparoscopic abdominoperineal resection (APR). Postoperative course was uneventful and patient was discharged at postoperative day 7. CONCLUSIONS: Our presented case is the first to describe prostate cancer solitary metastasis to anal canal and we always have to be aware of possible rare disease while assessing the patient with rectal bleeding. Biopsy most of the time is the only and the most reliable test to differentiate between the diseases.