||A keratoacanthoma is a benign, usually solitary, rapidly developing, epithelial neoplasm that arises most frequently on the sun-exposed areas of fair-skinned, elderly individuals. Multiple keratoacanthomas are rare and occur in patients who have a genetic predisposition. It is thought that keratoacanthomas arise initially fromhyperplasia of the infundihulum of a hair follicle with an associated metaplasia of the attached sebaceous glands. The etiology is unclear, however, actinic exposure, chemical carcinogens, and local trauma are all suspect. The lesion is a firm, dome-shaped nodule with skin-colored rolled edges and a central crater filled with keratin debris that clinically and histologically resembles a squamous cell carcinoma.
Keratoacanthomas usually begin as erythematous papules which enlarge rapidly over two to eight weeks to reach a maximum size of 1 to 2 cm and, if left alone, will involute spontaneously within six to twelve months, leaving behind a puckered scar.
a small early kerato acanthoma has arisen within the conchal bowl. The cup-like hyperplastic epithelium around the base can be seen and the central crater is granular and friable.