What characterizes a vesicle in dermatology?

A vesicle in dermatology is characterized as a small fluid-filled blister that typically measures 0.5 cm or less in diameter. This definition aligns with the common understanding of vesicular lesions, which are often seen in conditions such as herpes simplex, chickenpox, or contact dermatitis. The presence of clear or serous fluid within the cavity of the vesicle is a distinguishing feature, and its size relative to 0.5 cm helps differentiate it from other types of lesions such as bullae, which are larger.

The other options do not accurately describe vesicles. Elevated lesions larger than 0.5 cm would be classified as bullae, while flat lesions vary in classification depending on their characteristics and size. Thus, the precise measurement and fluid-filled nature are key aspects that correctly characterize a vesicle in dermatology.