Completely Regressed Primary Cutaneous Malignant Melanoma with Nodal and/or Visceral Metastases

Abstract

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 of uncertain significance, with only 30 cases reported in the literature. Herein, we detail five additional cases of complete histologic regression of a primary cutaneous melanoma, which were discovered upon presentation with metastatic disease. A pigmented lesion, or its remnant, coupled with historical information was strongly suggestive of cutaneous malignant melanoma. However, histologic examination of the lesions in toto using multiple levels, and in some cases immunohistochemical stains, failed to reveal residual melanoma. Our cases are typified by the presence of metastasis of malignant melanoma to regional lymph nodes, with the absence other suspicious lesions or other malignancies. Through these instructive cases, the concept of completely regressed primary cutaneous melanoma is reviewed and the literature critically appraised. When considering a diagnosis of completely regressed primary cutaneous melanoma, it is important that the cases be well‐documented and biopsy‐proven. All patients with a diagnosis of metastatic melanoma with an occult primary lesion require a thorough and complete skin examination and consideration of completely regressed cutaneous melanoma within the differential.