J Pathol Transl Med.  2019 Jul;53(4):266-269. 10.4132/jptm.2019.03.25.

Rectal Invasion by Prostatic Adenocarcinoma That Was Initially Diagnosed in a Rectal Polyp on Colonoscopy

• Yoon G
• Han MH
• Seo AN

• KMID: 2454607
• DOI: http://doi.org/10.4132/jptm.2019.03.25

Abstract

Despite anatomical proximity, prostatic adenocarcinoma with rectal invasion is extremely rare. We present a case of rectal invasion by prostatic adenocarcinoma that was initially diagnosed from a rectal polyp biopsied on colonoscopy in a 69-year-old Korean man. He presented with dull anal pain and voiding discomfort for several days. Computed tomography revealed either prostatic adenocarcinoma with rectal invasion or rectal adenocarcinoma with prostatic invasion. His tumor marker profile showed normal prostate specific antigen (PSA) level and significantly elevated carcinoembryonic antigen level. Colonoscopy was performed, and a specimen was obtained from a round, 1.5 cm, sessile polyp that was 1.5 cm above the anal verge. Microscopically, glandular tumor structures infiltrated into the rectal mucosa and submucosa. Immunohistochemically, the tumor cells showed alpha-methylacyl-CoA-racemase positivity, PSA positivity, and caudal-related homeobox 2 negativity. The final diagnosis of the rectal polyp was consistent with prostatic adenocarcinoma. Here, we present a rare case that could have been misdiagnosed as rectal adenocarcinoma.

Keyword

Prostatic adenocarcinoma; Colonoscopy; Rectum; Polyp

MeSH Terms

Adenocarcinoma*
Aged
Carcinoembryonic Antigen
Colonoscopy*
Diagnosis
Genes, Homeobox
Humans
Mucous Membrane
Polyps*
Prostate-Specific Antigen
Rectum
Carcinoembryonic Antigen
Prostate-Specific Antigen

Figure

• 

  Fig. 1. (A) Abdominopelvic computed tomography scan reveals an abnormally enhancing mass in the prostate gland that invaded the urinary bladder, both seminal vesicles, and the anterior wall of the distal rectum. (B) Representative image of the colonoscopy shows a sessile rectal mass about 1.5 cm from the anal verge.

• 

  Fig. 2. (A) Representative image of hematoxylin and eosin staining of the rectal biopsy specimen. (B) Tumor cells had prominent nucleoli.

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  Fig. 3. (A) Immunohistochemical staining for alpha-methylacyl-CoA-racemase positivity shows strong cytoplasmic expression in tumor cells but not in the normal rectal crypt. (B) Immunohistochemical staining for prostate specific antigen shows weak expression in tumor cells but no expression in normal cells. (C) Immunohistochemical staining for caudal-related homeobox 2 shows strong nuclear expression in the normal rectal crypt but not in tumor cells.

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