A white oral lesion disappears when the mucosa is stretched. What is the most likely diagnosis?

Leukoedema is a benign variation of normal oral mucosa characterized by a diffuse, bilateral, opalescent grayish-white appearance of the buccal mucosa. Its pathognomonic feature is that the white appearance disappears or diminishes significantly when the mucosa is stretched (diascopy/buccal stretch test). This is due to intracellular edema of the epithelial cells, which scatters light differently under tension. Leukoedema requires no treatment. White sponge nevus also appears as a white lesion but does NOT disappear with stretching. Leukoplakia and lichen planus are fixed lesions that do not disappear with stretching and require biopsy.