BACKGROUND
Retrorectal epidermoid cysts are uncommon developmental lesions that may remain asymptomatic for prolonged periods and can be difficult to distinguish from other presacral masses on clinical grounds. Magnetic resonance imaging is particularly useful for defining the lesion and its relationship to the rectum and surrounding pelvic structures. Complete surgical excision provides definitive histopathological diagnosis and treatment. This report describes a 40-year-old woman with a gradually enlarging, incidentally detected retrorectal epidermoid cyst followed radiologically for 13 years.
CASE REPORT
A 40-year-old woman had an incidentally detected cyst on routine ultrasound in 2012 and remained asymptomatic for more than a decade. A 13-year follow-up with serial imaging demonstrated gradual enlargement of the lesion from 20 mm to 70 mm, prompting surgical intervention. The patient subsequently underwent successful laparoscopic cyst excision. Histopathology demonstrated a cyst lined by stratified squamous epithelium with a prominent granular layer and lamellated keratin, consistent with an epidermal inclusion cyst. Estimated blood loss was 300 mL, and no transfusion was required. The patient was discharged on postoperative day 7 and remained asymptomatic at 3-month telephone follow-up.
CONCLUSIONS
A slowly enlarging asymptomatic retrorectal epidermoid cyst can remain clinically silent for many years. Progressive enlargement, increasing mass effect, diagnostic uncertainty, or concern for complications can justify definitive excision even in an asymptomatic patient. Careful preoperative imaging and meticulous dissection are important when a large cyst is closely related to the rectum and pelvic structures. Histopathological examination remains essential for definitive diagnosis.

Keywords: Case Reports; Laparoscopy; Rectum; Incidental Findings; Congenital Abnormalities