Which secondary lesion is a dried mass, remains of an oozing sore, possibly containing blood, pus, sebum, epithelial tissue and/or bacterial debris?

• A. Vesicle
• B. Pustule
• C. Crust
• D. Ulcer

Answer: (C)

Crust is the dried mass that forms on the skin after an oozing sore heals. It can contain dried blood, serum, pus, epithelial debris, and sometimes bacterial debris. That drying and layering during the healing process makes it a secondary lesion. A vesicle is a small blister filled with clear fluid, not a dried residue. A pustule is a raised spot filled with pus, typically moist rather than dried. An ulcer is a deeper break in the skin with tissue loss, not a dried surface. So the dried, crust-like mass fits the description precisely.