Case Report Highlights Rare Epidermoid Inclusion Cyst Behind the Ear

The clinical report was published in August 2026 in the Indian Journal of Otology by Dr. Diva Sharma and colleagues from the Maharishi Markandeshwar Institute of Science and Research.

Clinical Case Overview: 20-Year-Old Female

A 20-year-old woman presented with a slow-growing, painless retroauricular swelling and intermittent discharge for six months, occurring three years after an ipsilateral cortical mastoidectomy and tympanoplasty. Clinical examination showed a soft, fluctuant postauricular mass with a discharging fistula, while otoscopy confirmed an intact, well-healed neotympanum. Contrast-enhanced CT revealed a well-defined, thin-walled, hypodense lesion with peripheral rim enhancement filling the old mastoid cavity, without bony erosion or sclerosis. Under general anesthesia, the encapsulated mass was completely excised in one piece from the mastoid cavity. Histopathological analysis confirmed an epidermoid inclusion cyst lined by stratified squamous epithelium and filled with lamellar keratin, without dermal adnexa. The patient had a smooth postoperative recovery and remains disease-free on follow-up.

While mastoidectomy and tympanoplasty successfully treat chronic ear disease, surgical incisions or poor wound handling can accidentally implant skin cells into deeper tissues. These trapped cells shed keratin over time, forming a slow-growing mass that often stays unnoticed for years. As it enlarges or becomes inflamed, it can mimic conditions like acute abscesses, cysts, or recurrent cholesteatoma. Proper diagnosis is crucial to avoid wrong treatments like simple drainage instead of complete surgical removal. High-resolution, contrast-enhanced CT scans are key to pinpointing the cyst by showing clean borders and intact bone without destructive erosion.

Implications for Clinicians

Otolaryngologists and head and neck surgeons should maintain clinical suspicion for epidermoid inclusion cysts in individuals presenting with retroauricular masses and intermittent fistular discharge years following ear surgery. Preoperative contrast-enhanced temporal bone imaging is vital to delineate cyst margins, exclude cholesteatoma recurrence, and guide proper operative strategy. Complete surgical enucleation with intact capsule removal remains the definitive curative approach to prevent recurrence.

Reference

Sharma, D., Datta, G., Akhila, S., Jayan, A., & Pawar, S. (2026). A hidden sequel beneath the scar: Postmastoidectomy epidermoid inclusion cyst. Indian Journal of Otology, 32, 288–290.