Which statement best describes a sebaceous cyst?

• A. A serous-fluid filled cystic lesion
• B. A sack of epidermis under the skin, filled with keratin or sebum
• C. A blood-filled cavity that can become inflamed
• D. A subcutaneous fat deposit

Answer: (B)

Sebaceous (epidermoid) cysts are subcutaneous lesions that arise from epidermal tissue and become filled with keratinous material. The best description is a sack of epidermis under the skin, filled with keratin or sebum, because it captures both the epidermal origin and the keratinous contents that define these cysts. This differs from a serous-fluid filled cyst, which wouldContain clear serous fluid; a blood-filled cavity describes a hematoma; and a subcutaneous fat deposit refers to a lipoma. Clinically, these cysts present as a soft, mobile lump under the skin and are typically managed by excision of the cyst wall to prevent recurrence.