1502 | Epidermoid Cyst of the Urinary Bladder: A Rare Case Wenying Wang, Wencheng Lv , Ye Tian Keywords: epidermal‎cyst;‎diagnosis;‎urinary‎bladder‎diseases;‎urothelium;‎pathology. INTRODUCTION Epidermoid‎cyst‎of‎the‎urinary‎bladder‎is‎a‎very‎rare‎benign‎lesion.‎To‎the‎best‎of‎our‎knowledge,‎this‎case‎report‎of‎an‎epidermoid‎cyst‎located‎in‎the‎urinary‎bladder‎is‎the‎first‎in‎the‎English-language‎literature. CASE REPORT A‎31-year-old‎man‎was‎admitted‎to‎the‎hospital‎for‎a‎lesion‎of‎the‎urinary‎bladder‎discovered‎ on‎routine‎physical‎examination.‎He‎had‎a‎history‎of‎surgery‎for‎a‎perianal‎abscess‎3‎years‎ earlier.‎The‎urinary‎Nuclear‎Matrix‎Protein‎22‎(NMP‎22),‎serum‎cancer‎antigen‎19-9‎(CA‎19- 9)‎and‎carcinoembryonic‎antigen‎(CEA)‎levels‎were‎in‎the‎normal‎range.‎Ultrasonography‎ (US)‎examination‎showed‎an‎avascular‎onion-ring‎pattern‎with‎alternating‎hyperechoic‎and‎ hypoechoic‎rings.‎Computed‎tomography‎(CT)‎scan‎revealed‎a‎cystic‎mass‎in‎the‎right‎wall‎of‎ the‎bladder‎that‎had‎a‎density‎of‎15-30‎Hounsfield‎Unit‎(HU)‎without‎enhancement‎(Figure‎1). Surgical‎exploration‎revealed‎a‎3.0‎×‎3.2‎×‎2.5‎cm‎regularly‎shaped‎mass‎arising‎from‎the‎detru- sor‎muscle‎layer‎of‎the‎bladder.‎The‎mass‎was‎excised‎completely.‎Upon‎incising‎of‎the‎mass,‎ a‎large‎amount‎of‎cheesy‎keratinized‎material‎was‎found‎in‎the‎cavity.‎Hematoxylin‎and‎eosin‎ staining‎of‎the‎specimen‎revealed‎a‎typical‎epidermoid‎cyst‎that‎was‎lined‎with‎stratified‎squa- mous‎epithelium.‎No‎hair,‎sebaceous‎glands‎or‎other‎skin‎adnexa‎were‎seen‎within‎the‎cyst,‎nor‎ were‎there‎any‎findings‎suggestive‎of‎dysplasia‎or‎malignancy‎(Figure‎2).‎The‎patient‎did‎well‎ postoperatively,‎and‎no‎recurrence‎was‎noted‎at‎the‎18-month‎follow-up. DISCUSSION Epidermoid‎cyst‎is‎lined‎with‎stratified‎squamous‎epithelium‎that‎contains‎a‎granular‎layer‎and‎ is‎filled‎with‎keratinous‎material‎that‎is‎often‎in‎a‎laminated‎arrangement.‎These‎cysts‎are‎rare‎ Corresponding Author: Ye Tian, MD Department of Urology, Beijing Friendship Hospital, Capital Medical University, 95 Yong an Road, Xuanwu District, Beijing, 100050, China. Tel: +86 186 0116 6102 Fax: +86 106 3139 043 E-mail: miniaowwy@yahoo.com.cn Received July 2012 Accepted January 2013 Department of Urology, Beijing Friendship Hospital, Capital Medical University, 95 Yong an Road, Xuanwu District, Beijing,100050, China. CASE REPORT Case Report 1503Vol. 11 | No. 02 | March- April 2014 |U R O LO G Y J O U R N A L Epidermoid Cyst of the Urinary Bladder | Wang et al in‎children‎but‎are‎common‎in‎adults,‎their‎most‎frequent‎lo- cations‎are‎the‎face,‎scalp,‎neck,‎and‎trunk.‎Epidermoid‎cysts‎ are‎rarely‎seen‎in‎solid‎organs.‎A‎few‎cases‎of‎epidermoid‎ cysts‎located‎at‎rare‎sites‎such‎as‎the‎kidney‎and‎ureter‎have‎ been reported in the literature.(1,2)‎To‎the‎best‎of‎our‎knowl- edge,‎epidermoid‎cyst‎of‎the‎urinary‎bladder‎has‎not‎been‎ reported‎previously. Epidermoid‎cysts‎are‎usually‎asymptomatic,‎although‎symp- toms‎may‎occur‎when‎the‎cysts‎are‎large.‎They‎may‎become‎ infected,‎or‎uncommonly,‎they‎may‎rupture,‎causing‎a‎for- eign‎body‎reaction.‎Symptoms‎of‎flank‎pain,‎dysuria,‎or‎gross‎ hematuria‎are‎able‎to‎happen‎in‎patients‎with‎renal‎epider- moid‎cysts.(1)‎Results‎of‎routine‎laboratory‎tests‎are‎usually‎ normal‎and‎not‎diagnostic.‎Keratinized‎material‎in‎a‎urine‎ sample‎may‎suggest‎an‎epidermoid‎cyst‎in‎the‎urinary‎tract.(2) Epidermoid‎cysts,‎which‎are‎true‎congenital‎primary‎meso- thelial‎cysts,‎have‎an‎epithelial‎or‎mesothelial‎cell‎lining,‎and‎ are‎thought‎to‎be‎developmental‎in‎origin.‎Different‎theories‎ have‎been‎postulated‎for‎the‎presence‎of‎epidermoid‎cyst‎in‎ extraordinary‎sites‎such‎as‎kidney,‎spleen,‎brain,‎and‎ureter.‎ In‎the‎kidney,‎it‎is‎suggested‎that‎this‎type‎of‎cyst‎could‎origi- nate‎from‎the‎embryonic‎remnant‎of‎Wolffian‎ducts.(2) In this patient,‎the‎cyst‎may‎have‎arisen‎from‎surgical‎implantation‎ of‎epidermal‎tissue‎secondary‎to‎perianal‎abscess‎surgery. On‎ US,‎ the‎ classic‎ appearance‎ is‎ typically‎ alternating‎ of‎ avascular‎hyperechoic‎and‎hypoechoic‎rings,‎which‎was‎de- scribed‎as‎an‎onion-ring‎pattern.‎On‎CT‎scan,‎epidermoid‎ cysts‎appear‎as‎homogenous,‎well-defined,‎ round‎or‎oval,‎ low-enhancing‎or‎non-enhancing,‎hypodense‎lesions.‎Cysts‎ should‎not‎demonstrate‎any‎enhancement‎after‎the‎adminis- tration‎of‎gadolinium. Most‎epidermoid‎cysts‎don't‎cause‎problems‎or‎require‎treat- ment,‎but‎if‎they‎are‎a‎cosmetic‎concern,‎or‎if‎they‎rupture‎ or‎ become‎ infected,‎ they‎ usually‎ are‎ removed‎ surgically.‎ Epidermoid‎cysts‎are‎usually‎benign,‎but‎there‎is‎a‎reported‎ 1‎to‎3‎percent‎rate‎of‎malignant‎transformation.‎Squamous‎ cell‎carcinoma‎has‎been‎observed‎originating‎from‎squamous‎ epithelium‎located‎in‎the‎testis,‎as‎well‎as‎from‎an‎intracra- nial‎epidermoid‎cyst.(3) Although a lesion such as this has not‎been‎demonstrated‎in‎the‎urinary‎bladder,‎excision‎of‎this‎ cyst‎is‎the‎most‎appropriate‎management. Although‎rare,‎epidermoid‎cyst‎of‎the‎urinary‎bladder‎should‎ be‎considered‎in‎the‎differential‎diagnosis‎of‎incidentally‎dis- covered‎bladder‎lesions. CONFLICT OF INTEREST None declared. REFERENCES 1. Dadali M, Emir L, Sunay M, Ozer E, Erol D. Intrarenal epidermal cyst. Kaohsiung J Med Sci. 2010:26:555-7. 2. Ishizaki H, Iida S, Koga H, Shimamatsu K, Matsuoka K. Epidermoid cyst of the ureter: A case report. Int J Urol. 2007;14:443-4. 3. Chiu MY, Ho ST. Squamous cell carcinoma arising from an epider- mal cyst. Hong Kong Med J. 2007;13:482-4. Figure 1. Computed tomography scan revealed a cystic mass in the right wall of the bladder that had a density of 15-30 Houns- field Unit without enhancement. Figure 2. Hematoxylin and eosin staining of the specimen revealed a typical epidermoid cyst that was lined with stratified squamous epithelium (40×10).