Which lesion is a movable, skin-colored subcutaneous cyst on the face, back, ears, or groin, containing a keratin-filled sac and may become inflamed?

• A. Epidermal inclusion cyst
• B. Dermatofibroma
• C. Pilar cysts
• D. Lipoma

Answer: (A)

This describes an epidermal inclusion cyst. It’s a mobile, skin-colored subcutaneous nodule that contains keratin within a sac lined by squamous epithelium, and it often becomes inflamed if infected. The location on the face, back, ears, or groin fits common sites for these cysts, and the keratin-filled contents are a hallmark feature.

Inflammation occurs when bacteria infect the cyst, leading to redness, tenderness, and sometimes drainage of keratin material. The central punctum (a small opening) can be a clue, reflecting a blocked pore or hair follicle origin.

Dermatofibroma is a firm, fibrous skin lesion without a true cyst or keratin-filled sac. Pilar cysts are keratin-filled but typically arise from hair follicles and are most common on the scalp, not the face, back, ears, or groin. Lipomas are soft, fatty, usually non-inflammatory subcutaneous masses that lack keratin contents.