Abstract: A 78-year-old male presented with bilateral subcutaneous buttock masses for 15 years. Dermatological examination showed a 12 cm-diameter erythematous, warm, soft, fluctuant and poorly mobile mass on the left buttock, and an 8 cm-diameter firm, well-demarcated mass with moderate mobility on the right. Imaging confirmed epidermoid cysts, and surgical resection was performed. Pathology revealed epidermoid cysts bilaterally; the left mass was associated with squamous epithelial papillary hyperplasia and focal high-to-moderately differentiated squamous cell carcinoma. No recurrence was noted during 5-month follow-up.

Key words: epidermoid cyst, malignant transformation, squamous cell carcinoma