Infected intraosseous epidermoid cyst in the right ankle: a case report

Epidermoid cysts, also known as follicular cysts, are benign tumors that typically arise from hair follicle infundibulum. These cysts are most commonly seen in subcutaneous tissues, though intraosseous epidermoid cysts (IEpC) are rare, with few reports of their occurrence in the phalanges and even more infrequently in the ankle. This case report discusses a 61-year-old male who presented with progressively enlarging swelling on the lateral aspect of his right ankle. Initially asymptomatic, the lesion became painful, inflamed, and discharged purulent material, prompting concern for an infection. Diagnostic imaging, including magnetic resonance imaging (MRI), suggested a possible infected ganglion or tumorous cyst. Laboratory tests confirmed mild leukocytosis and elevated inflammatory markers. Following unsuccessful drainage, surgical excision was performed, revealing a 7×5×2.4 cm cystic mass. Histopathological examination confirmed the diagnosis of an epidermoid inclusion cyst. The patient’s recovery was uneventful, with no recurrence of symptoms.