Description

A 69-year-old man with a medical history of HIV infection and prostate cancer presented to our practice complaining of lower abdominal pain and rectal bleeding. Prostate cancer was diagnosed in 1990, for which the patient underwent radiation therapy, bilateral orchiectomy and was managed with flutamide for several years. Twelve years after the initial diagnosis, he underwent prostate cryoablation. However, prostate-specific antigen continued to rise from 5.98 to 107.43 over a span of 6 months.

CT scan of the abdomen and pelvis revealed retroperitoneal and right iliac adenopathy, a nodal mass at the level of kidneys measuring 3.8×2.4 cm. The patient had a colonoscopy and a 3 cm oozing soft mass was found at the rectal verge (figure 1). Biopsy was done, which stained positive for prostatic acid phosphatase and CDX2 consistent with poorly differentiated adenocarcinoma metastatic from prostate (figure 2).1 ,2

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Figure 1

Colonoscopy showing a soft oozing mass.

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Figure 2

Rectal biopsy consistent with metastatic prostate cancer.

Prostate cancer is the second most common cancer in men with metastasis commonly occurring in the bones.3 On rare occasions, it metastasises to the rectum.4 The anatomic route can be via lymphatic drainage, since prostate and rectum share a common route, and/or via direct invasion of the rectum by the prostate cancer and/or via metastatic implant while performing a needle biopsy of the prostate.5–7

In conclusion, infiltration of the rectum by prostate cancer cells presents with abdominal pain and rectal bleeding; physicians should regularly assess for gastrointestinal symptoms and perform regular rectal examinations in patients with prostate cancer.