Complete regression of primary malignant melanoma.

Over the years, histopathologic studies to determine the nature and significance of regression in malignant melanoma have yielded different results. At least in part, this most likely reflects differences in the definition of what constitutes regression. Although partial regression is relatively common, complete regression is rare. It has been said that complete regression of a primary lesion is associated with metastatic disease, but the evidence for this is largely anecdotal-the literature contains only case reports and small series. We found 2 cases of complete regression in our dermatopathology database. Metastatic disease was identified in both cases; in 1 case, the suspicion of melanoma was raised on the initial biopsy and subsequent workup revealed lymph node metastasis. These cases illustrate the histologic features of a completely regressed primary melanoma and add credence to the theory that completely regressed melanoma is associated with a poor outcome.