PDF: Keratoacanthoma in the cutaneous area of the upper lip: a case report

Keratoacanthoma (KA) is a common benign skin lesion composed of keratinized squamous cells that originates in the hair follicle.


The clinical and histopathological features of KA are similar to squamous cell carcinoma (SCC) of the skin, which often complicates a differential diagnosis. 

See also: PDF: Regional odontodysplasia: a case report

KA usually appears as a skin-colored papule with a central keratin core similar to a "volcano": it grows for a period of 2 to 4 weeks, reaching up to 2 cm at its largest. The tumor usually appears on sun-exposed areas in middle-aged or older patients, which suggests an etiological association with ultraviolet light exposure. Other factors that may contribute to the development of KAs are genetic factors, immunosuppression, potentially carcinogenic chemicals, viruses, and trauma. Clinically, KA may appear as a sporadic solitary lesion or as multiple lesions associated with hereditary syndromes.

KAs can be associated with a condition called Muir-Torre syndrome, which involves multiple sebaceous neoplasms and internal malignancies such as colon cancer; in such a situation, KA may be present in anybody region.

The solitary type of KA has a typically rapid development, growing in areas that are exposed to the sun and tending to resolve spontaneously within 6 months. In most cases of spontaneous regression, however, formation of an aesthetically unpleasant scar is observed. The recurrence of KA is unusual, being reported around 3-5% of the time.

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