Completely regressed primary cutaneous malignant melanoma with nodal and/or visceral metastases: A report of 5 cases and assessment of the literature and diagnostic criteria

Background: Partial regression of primary cutaneous malignant melanoma is not uncommon and may predict a higher likelihood of metastasis and decreased survival. Complete histologic regression of a primary cutaneous melanoma is a rarer occurrence, with only 34 cases reported in the English-language or English language-summarized literature. Observation: We detail 4 cases of complete histologic regression of primary cutaneous melanoma, discovered at presentation with metastatic disease. A pigmented lesion or its remnant, coupled with historical information, was strongly suggestive of cutaneous melanoma. Histologic examination of the lesions, using multiple levels and immunohistochemical stains, failed to reveal residual melanoma. Our cases are typified by the presence of metastasis of melanoma to regional lymph nodes, with the absence of other suspect skin lesions or malignancies. In addition, we present a fifth case involving a completely regressed lesion on the scalp in a patient with cerebral melanoma metastasis and comment on the implications of this case to accepted diagnostic criteria, proposing that consideration of modification to the criteria be entertained. Conclusion: The concept of completely regressed primary cutaneous melanoma is reviewed and the literature critically appraised. When one considers a diagnosis of completely regressed primary cutaneous melanoma, cases must be well documented and biopsy proven. Patients with metastatic melanoma and an occult primary lesion require a thorough skin examination, with serious consideration given to the possibility of completely regressed cutaneous melanoma.