A keratoacanthoma is a rapidly growing skin tumour frequently seen on areas of sun exposure in older patients. The rate of growth is impressive. Frequently they can grow from nothing to a several centimetre-sized tumour within several weeks. They often have a central keratotic core surrounded by a shoulder of inflamed skin. They’re often dry and seldom bleed. Rarely there can be multiple tumours that form simultaneously.

This is a confusing area even for dermatopathologists. The skin cells appear similar to squamous cell carcinoma. But KA very rarely metastasizes. If left untreated, the vast majority will regress leaving an atrophic scar. However, while present the KA can invade the surrounding tissue.

Numerous studies have identified human papillomavirus within the tumour. Some argue that KA may be an extremely rapidly growing wart. This may explain the speed of growth and the lack of metastasis, though this concept isn’t widely accepted within the dermatologic community.

The optimal treatment for KA is surgical removal. Sometimes it’s difficult to determine the margin of the tumour, and it’s possible that the KA may recur. If this were to happen, the recurrence may be seen within one to two weeks post-surgery. An alternative treatment is intralesional injection of methotrexate. Finally, radiotherapy has been used with success in patients with large KA who are not good surgical candidates.

Tumours that arise on the face are best treated by plastic surgery or surgical dermatology in order to ensure complete removal while preserving the cosmetic outcome.

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