Final answer:
Leukoedema is the most likely diagnosis for a white diffuse lesion on the buccal mucosa that disappears upon stretching, which is considered a normal mucosal variant and is common among African-American adults.
Step-by-step explanation:
The most likely diagnosis of a white diffuse lesion with a wrinkled appearance on the buccal mucosa that disappears upon stretching is Leukoedema. Conditions such as Lichen planus, Candidiasis, Linea alba, and White sponge nevus typically do not exhibit the characteristic of lesions that disappear when the mucosa is stretched. Leukoedema is more common in African-American adults and is considered a variant of normal oral mucosa that does not require treatment.