What is the term for a flat pigmented lesion on the skin?

A flat pigmented lesion on the skin is referred to as a macule. Macules are small, flat changes in skin color that can be brown, red, or white, and they do not produce any elevation or depression in the skin's surface. This characteristic is key in distinguishing macules from other types of skin lesions.

In contrast, a papule is a raised lesion that is typically small and solid, while a vesicle is a fluid-filled blister. A patch is similar to a macule but larger in size, generally over 1 cm, and can also be pigmented or colored, but it is not exclusively flat as macules are. Therefore, macules fit the description of a flat pigmented lesion most precisely within dermatological terms.