FIGURE 1.

Keratoacanthoma histological features. (A) (H&E, 40×) Low-power view revealing the morphological aspects of keratoacanthoma, such as well-delimited hyperplastic, crateriform endophytic or exophytic epithelia with a central keratin-containing crater and (B) presence of sharp outline between tumor nests and the stroma (outline), and tumor cells with prominent nucleoli and eosinophilic ground-glassy cytoplasm. (C) Microscopic view of the keratoacanthoma shows intense chronic inflammatory cell infiltrate (arrows) within the connective tissue and juxtaposed to the tumoral epithelial cells (H&E, 200×). Actinic elastosis are present next to the lesion (H&E, 200×) and nuclear hyperchromatism (darkening of nucleus; outline; H&E, 200×) are observed in keratoacanthomas.