Multiple primary melanoma with the Meyerson phenomenon in a young patient.

Meyerson phenomenon (MP), also called halo eczema or halo dermatitis, was first described in 1971 as a symmetric eczematous halo around acquired melanocytic nevi. Since then, cases of MP have been described in any kind of melanocytic nevi and also in non-melanocytic tumors. To the best of our knowledge, only four cases of melanoma associated with MP have been reported. We report the singular case of a young adult diagnosed with two primary melanomas in the context of dysplastic nevi syndrome who presented several flares-up associated with MP in both benign and malignant melanocytic tumors. MP usually manifests as a halo of erythema and scaling similar to plaques of eczema symmetrically surrounding a central cutaneous tumor. Dermoscopic findings of MP show it as similar to other forms of dermatitis. Histopathology usually shows epidermal changes compatible with subacute eczematous dermatitis. Immunohistochemical studies have shown inflammatory infiltrate composed mainly of CD4+ lymphocytes, which supports the suggested pathogenesis of an immune-mediated reaction. It usually resolves spontaneously, and the use of topical corticosteroids has a good response. In conclusion, MP is not specific for benignity, even when multiple simultaneous lesions are affected. Inflammatory changes can make melanocytic lesions difficult to interpret, both on dermoscopic regression features and on histopathologic examination. Therefore, it is recommended to consider the complete excision of melanocytic lesions with atypical vessels and/or extensive regression phenomena more than 50%. Further studies are needed to know whether the presence of a melanoma could induce a remote immune response in other benign melanocytic lesions.