A Paravaginal Epidermal Inclusion Cyst Presenting as Chronic Bilateral Pelvic Pain

Background: Epidermal inclusion cysts are benign masses that typically present as subcutaneous nodules with a visible central punctum. These cysts are lined with stratified squamous epithelium and become filled with keratin as they grow below the skin. In the case of unmanaged cyst growth, surrounding structures may be affected, resulting in pain and impairment of bodily function. Epidermoid cysts may be seen anywhere on the body, often coinciding with inflamed hair follicles. These cysts are one of the most common types of vulvar cysts, but are rarely seen originating deep in the paravaginal region. Previous literature has reported a few cases of paravaginal epidermoid cysts, but there is limited clinical information regarding epidermoid cysts without a visible protuberance on physical examination. The lack of reported cases suggests that this clinical presentation is rare. Case Presentation: A 21-year old nulliparous female initially presented to the clinic with chronic bilateral pelvic and lower back pain that started one week prior to her menstrual cycle. The patient reportedly faced similar symptoms for many months with progressive pain and bloating. She disclosed a known history of fibromyalgia, but denied any history of trauma to her pelvic or lower back area. Given the patient’s complaints, the patient was initially treated with a Depo-Provera injection for possible endometriosis and was counseled on further steps if the injection did not provide relief of her symptoms. The patient returned to the clinic months later for evaluation of a pelvic mass found in the emergency department via imaging. The patient stated that the Depo-Provera injection did not alleviate her symptoms and reported additional symptoms of frequent urination, and urinary retention requiring increased effort. Diagnostic imaging revealed an approximately 6 cm x 4 cm tender cystic mass in the left lower pelvis displacing the left posterior wall of the bladder and abutting the rectum. There was no visual distention of the perineum, vulva, or vagina. The unusual location of the cyst concealed its visualization on physical examination, an atypical presentation of a subcutaneous cyst. Surgical excision was performed and pathological analysis revealed a deep epidermal inclusion cyst filled with caseous debris extending into the ischiorectal fossa. Conclusion: This case study examines an unusual presentation of a symptomatic paravaginal epidermal inclusion cyst extending into the ischiorectal fossa without a visual protuberance on examination nor identifiable risk factors such as prior trauma and surgery.