- Keratoacanthomas (KAs) are rapidly-growing benign neoplasms of the epidermis which may be a benign variant of Skin Squamous Cell Carcinoma (SCC). The etiology of KAs is unclear but some relationship with chronic sun-exposure is likely given the predilection for sun-exposed skin of the arms although any body surface can be affected.
- KAs appear as solitary dome-shaped papules with smooth rolled borders and a central keratin-filled crater. Histologically, KAs display atypical keratinocytes and impressive central hyperkeratosis that manifests as the keratin-filled plug. In some cases, histological differentiation from SCC can be difficult.
- KAs grow rapidly, within weeks, and if left untreated may spontaneously regress over months. These neoplasms are almost always benign although 1-2% are locally invasive. However, in many cases gross and histological differentiation from SCC can be challenging.