During a physical assessment, what term should the nurse use to describe a flat, poorly defined mass on the sole caused by pressure?

The term used to describe a flat, poorly defined mass on the sole caused by pressure is "callus." A callus typically forms in response to repeated friction or pressure on the skin, leading to thickened, hardened areas. This reaction is a protective mechanism of the skin, aimed at preventing deeper damage or injury. Calluses are generally not painful, although they can become uncomfortable if they grow too thick or if they are located in a high-friction area.

In contrast, other terms refer to different skin conditions or formations. A blister is a fluid-filled lesion that forms as a result of friction or burns, while a corn is a small, thickened area of skin that usually has a defined shape and often occurs over a bony prominence, causing discomfort. A wart is a viral infection on the skin that appears as a raised growth and can have a rough texture. Each of these conditions differs in characteristics and causes, highlighting why "callus" is the most appropriate term in this scenario.