Case Report 524 CASE REPORT Ectopic Prostatic Tissue in the Right Paracolic Gutter: A Case Report Bokyung Ahn1, Youngseok Lee1, Ki Choon Sim2, Jeong Hyeon Lee1* Ectopic prostatic tissue (EPT) is fairly uncommon; however, when reported, it is most often found in the male genitourinary tract. Since extragenitourinary EPT is very rare, it is extremely difficult to properly diagnose preop- eratively.(1-3) This article describes a unique case of EPT found in the right paracolic gutter. Keywords: ectopic prostatic tissue; extragenitourinary tract; paracolic gutter INTRODUCTION Ectopic prostatic tissue (EPT) is fairly uncommon; however, when reported, it is most often found in the male genitourinary tract. Since extragenitourinary EPT is very rare, it is extremely difficult to properly diagnose preoperatively.(1-3) This article describes a unique case of EPT found in the right paracolic gutter. CASE REPORT A 73-year old man with a 6-year history of hepatocellular carcinoma (HCC) showed a 1.7-cm-sized hyperenhanc- ing mass in the right paracolic gutter in follow-up abdominal computed tomography (CT) (Figure 1). He had been treated with transarterial chemoembolization and radiofrequency ablation without surgery. Follow-up abdominal CT revealed a newly noted mass in the right paracolic gutter, which was suspicious of metastatic HCC and neces- sitated surgical resection. Gross examination showed a relatively well-demarcated nodule with partly cystic appearance (Figure 2). Micro- scopic examination showed a nodule full of simple, dilated glandular structures with corpora amylacea present in several of the glandular lumina. The background stroma showed a fibrous to partly loose appearance with bland, spindled cells (Figure 3a). The glands had both a luminal and a basal layer of cuboidal to columnar cells, remi- niscent of a benign hyperplastic prostatic epithelium. Prostatic-specific antigen immunostaining showed strong, diffuse positivity in the luminal cells that further confirmed the prostatic nature of the nodule (Figure 3b). DISCUSSION Review of the literature revealed few reports of EPT outside the genitourinary tract including the rectum, presacral or perirectal fat, anal canal, spleen, and cervix.(4-7) EPT within or near the gastrointestinal (GI) tract has a left-side preference, especially in the anorectal region. To the best of our knowledge, there are no published reports describ- ing an EPT on the right colon. 1Department of Pathology, Korea University Anam Hospital, Korea University College of Medicine, Seoul, Korea 2Department of Radiology, Korea University Anam Hospital, Korea University College of Medicine, Seoul, Korea *Correspondence: Department of Pathology, Korea University Anam Hospital, Korea University College of Medicine, 73, Inchon-ro, Seongbuk-gu, Seoul 02841, Korea Tel: 82-10-5919-5753. Fax: 82-2-920-6576. E-mail: jhleepath@gmail.com. Received October 2019 & Accepted December 2019 Urology Journal/Vol 18 No. 1/ January-February 2021/ pp. 134-135. [DOI: 10.22037/uj.v0i0.5593] Figure 1. Axial contrast-enhanced CT of the abdomen and pelvis (portal phase). An incidental lesion was found in the right paracolic gutter area during follow-up after HCC treatment. In the next fol- low-up examination, the size was slightly increased, and the opera- tion was performed under suspicion of HCC metastasis. Figure 2. After serial section of the fibroadipose tissue, the cut sur- face shows a relatively well-demarcated white-colored mass with multiloculated cystic spaces, measuring 1.6 x 1.4 cm. Vol 18 No 1 January-February 2021 20 There are three hypotheses regarding the pathogenesis of EPT.(8) One is faulty embryogenesis, as both the rec- tum and bladder originate from the endodermal cloaca. When morphogenetic organization fails in the dorsal cloacal compartment, which is destined to become the rectum, the tissue retains the ability to produce anterior cloacal structures, which later forms the bladder, ure- thra, and prostate. A second hypothesis is aberrant loca- tion of prostatic stromal tissue, which is thought to in- duce the local epithelium to differentiate into prostatic epithelium.(9) The third hypothesis is based on seeding of viable prostatic tissue during surgery or biopsy of the prostate, which is mostly conducted in a transurethral or transrectal manner. No single hypothesis has been confirmed or explains the location of EPT in the right paracolic region with no previous history of biopsy or surgery of the prostate. In our case, pathologic confirmation of EPT was im- portant in determining further treatment and prognosis. Preoperative diagnosis of EPT outside the urinary tract is extremely difficult; however, correct diagnosis is cru- cial to avoid malignant transformation.(5) Although Ha- lat et al. reported similar pathologic findings of 80% of EPT cases to those of the central zone of the prostate,(1) our case showed features reminiscent of the peripheral zone of the prostatic gland. There were no signs of dys- plastic or malignant change in our case. Since there is no explanation for the location of EPT in our case, more cases should be collected, and further studies should be conducted. In conclusion, misdiagno- sis of EPT may lead to unneeded treatment and patient anxiety; therefore, proper suspicion and correct diagno- sis are important. ACKNOWLEDGEMENT This study was approved by the Institutional Review Board of Korea University Anam Hospital (IRB No. 2018AN0171). CONFLICT OF INTEREST No potential conflicts of interest relevant to this article are reported. REFERENCES 1. 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