Keratoacanthoma: when to observe and when to operate and the importance of accurate diagnosis.

Although keratoacanthoma regresses spontaneously, treating physicians seldom allow these lesions to progress through their natural course. We describe two cases of skin lesions, the first being a keratoacanthoma, which enlarged rapidly and then involuted with minimal scarring. The second lesion was initially misdiagnosed and failed to respond to medical management. An accurate diagnosis of squamous cell carcinoma was not made until the lesion had become deeply invasive. These two lesions have helped clarify our thoughts about the observation of keratoacanthomas, the need for frequent patient follow-up when a lesion is not surgically ablated, and the importance of providing the pathologist with an adequate biopsy specimen for diagnostic purposes.