Hematoxylin-eosin−stained sections of the forehead specimen showed a large tumor composed of nests of squamous epithelial cells. The lesion, which had a cup-shaped architecture and a central keratinous plug, consisted primarily of numerous islands of keratinizing epithelium that permeated the dermis. The largest keratinocytes contained ample amounts of “glassy” cytoplasm. No sebaceous differentiation was noted. The clinical and microscopic findings were consistent with a keratoacanthoma.
A Rapidly Growing Nodule and Dome-Shaped Yellow Papules on the Face—Diagnosis. Arch Dermatol. 2005;141(4):515-520. doi:10.1001/archderm.141.4.515-d