ACR Codes: 8.3
Epidermoid cyst of the testis is a benign, well-circumscribed squamous-filled cyst representing less than 1% of all testicular tumors. 25% of cases occur in the first 2 decades of life. Reported cases are limited to whites and Asians. Multiple cysts have been reported, including one case of bilateral cysts. There is a slightly higher prevalence in the right testis.
Etiology is unknown, but they are believed to be a form of teratoma with monodermal development of the ectoderm. Alternately, they may be embryonic inclusion cysts.
Typically presentation is a discrete palpable nodule within the testis. Patient may or may not have symptoms of epididymitis.
On gross examination, there is a well-circumscribed cyst filled with flaky or lumpy yellow-white material.
Histologically, stratified squamous epithelium, dense fibrous tissue wall, focal calcifications, and acellular keratotic debris may be seen.
Sonographically, they are seen as a well-circumscribed hypoechoic mass with internal echoes or an onion-skin lamellated appearance. They should not demonstrate increased vascularity.
On MRI, reported findings include low intensity rim surrounding a higher intensity ring surrounding a central area of low intensity (T1 and T2) or alternating concentric rings of low and high intensity (T1 and T2).
Reference(s): Husain AN, Selby DM, Dehner LP. The Male Reproductive System Including Intersex Disorders. In: Stocker JT and Dehner LP. Pediatric Pathology, 2nd ed. Philadelphia: Lippincott, Wiliams, & Wilkins 2002:939-975.