RESUMEN
INTRODUCTION AND IMPORTANCE: Epidermoid cysts are developmental cysts of the retrorectal space. They are benign lesions resulting from ectodermal inclusion during neural tube closure. Generally, they are misdiagnosed given that symptoms are often vague and nonspecific. They have a high infection rate (up to 30%) and can be easily mistaken for perirectal abscesses. CASE PRESENTATION: We present a case of an epidermoid cyst in a 58-year-old woman with a retrorectal cyst mistaken for a perianal abscess, which was initially incised and drained and then, after MRI investigation, an anterior resection was performed. CLINICAL DISCUSSION: Epidermoid cysts have a high infection rate (up to 30%). Infected cysts can be easily mistaken for perirectal abscesses, pilonidal disease, or fistulae in ano. CT (computed tomography) used in conjunction with MRI (Magnetic Resonance Imaging) is the gold standard for establishing the diagnosis. A biopsy is never indicated. Surgery is the best treatment, even for asymptomatic lesions. CONCLUSION: Epidermoid cysts are rare and generally misdiagnosed. In fact, symptoms are often vague and nonspecific. Radiologic imaging (especially MRI) is essential for surgical planning and biopsy should be avoided. Once a presacral lesion is diagnosed, even if the patient is asymptomatic, complete resection remains the treatment of choice because of the risk of infection.