Two thirds of keratoacanthomas occur on the face; the rest occur elsewhere including the ears (usually sun damaged, hair bearing skin). They arise from hair follicle skins cells for unknown reasons. The lesions usually start as a small pink papule which rapidly enlarges over the following few months. Eventually (6-12 months), the lesions spontaneously regress, leaving an ugly scar. Many are removed to exclude squamous cell carcinomas (SCCs) and to prevent scarring.

Key learning points from the video

• 74-year-old patient with an evolving lesion on his left arm
• Lesion on the patient started as a small scaling lesion on the arm
• Developed by building up around the base with a central evolving area
• Likely that under the scale will be ulceration
• Diagnosis of keratoacanthoma variant of a squamous cell carcinoma derived from pilosebaceous cells
• For excision it requires good surgical margins but taking as little tissue as possible
• Langer’s lines or skin tension lines will dictate the direction of the excision
• Lignocaine with adrenaline can be used for local anaesthetic
• Elliptical excision is required in this case in one fluid motion
• Cut down to subcutaneous tissue so the lesion is floating up
• Keratoacanthomas generally do not extend deeper into underlying tissues
• Start from the apex and work backwards once lateral excisions in place
• It is important to see subcutaneous flat underneath the lesion with a yellow sheen underneath
• Check for any signs that invasion has occurred under the lesion
• It is important to ensure the excision is deep enough so that closure is made easier
• Suture lesion at the two thirds and third point to then close across the middle