Recurrent squamous cell carcinoma of the skin.

A retrospective analysis of all patients having the diagnosis of squamous cell carcinoma of the skin at a single hospital over a ten-year period was performed. These lesions are less common than both basal cell carcinomas and malignant melanomas. Noninvasive squamous cell carcinomas were not observed to recur. There was a 20% incidence of recurrence in 86 patients with invasive squamous cell carcinoma. The presence of solar changes in the skin did not obviate recurrence. The larger, less differentiated lesions had a greater probability of recurrence. When the depth of invasion of the lesions were determined, it was found that only the lesions that penetrated to Clark's Level IV or V recurred. Squamous cell carcinomas that penetrate to this depth have the potential to recur and metastasize to regional lymph nodes and should be considered malignant lesions, even if they are associated with actinic skin changes.