Which of the following is NOT a characteristic of keratoma?

A keratoma, commonly referred to as a corn or callus, is a thickening of the outer layer of skin (stratum corneum) that develops in response to pressure or friction. This thickening serves as a protective mechanism against irritation.

The first option, thickened skin, is indeed a characteristic of keratomas because they are defined by that very thickening as a physiological response to friction. The option concerning being caused by friction is also accurate, as keratomas typically arise due to repetitive stress or pressure on a particular area of skin. Additionally, it is possible for keratomas to develop into calluses, as both involve hyperkeratosis—the thickening of the stratum corneum—due to similar causes.

The option indicating pigmented color is not a defining characteristic of keratomas. While keratomas can sometimes appear yellow or gray due to the accumulation of keratin, they are primarily identified by their texture and thickness rather than pigmentation. Therefore, the claim about pigment color does not align with the fundamental characteristics of keratomas, making it the correct response to the question.