Keratoacanthomas (KAs) are fast growing skin lesions occurring across the body, mainly in sun exposed areas of the skin. They are rapidly evolving tumours made up of keratinising squamous cells which originate in pilosebaceous follicles.
They can look very similar to a well differentiated SCC. Their growth behaviours can be what distinguishes them from a SCC. A KA may grow rapidly over 12 weeks. They start life as a small, firm skin coloured rounded papule. They are largely symmetrical, dome-shaped with a smooth shoulder of skin and a central keratin core. Typically the size is 1-2cm and can get larger. Rarely a KA can appear yellow and therefore almost sebaceous in nature.
In some situations a KA may occur following an injury to the skin. Sun exposed sites are a key contributor to their anatomical positioning. Males are more likely to be affected than females.
The general rule of thumb is, it is difficult to clinical and histologically distinguish between a KA and SCC therefore a USC referral should be made to secondary care for further management. If left untreated many are self-resolving. (18)