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In this report, we present a novel case of pseudomelanoma, similar to that seen in a recurrent/traumatized nevus, in pre-existing nevi in a 36-year-old man a few months after recovering from an episode of severe Stevens-Johnson syndrome. The mechanism responsible for the atypical transformation of these nevi is likely the release of cytokines and growth factors in the microenvironment during the repair/regeneration process. It is important to be aware of this phenomenon, and specific inquiry about potential recent blistering skin disorder in addition to the other causes of trauma should be made when dealing with cases of pseudomelanoma to avoid misdiagnosis.

We present a case of a 6-year-old girl with recessive dystrophic epidermolysis bullosa (EB) who presented with a large pigmented lesion clinically concerning for melanoma. After histological examination and fluorescent in situ hybridization analysis, diagnosis of EB nevus was performed. EB nevi are benign melanocytic neoplasms with histological findings similar to recurrent nevi occurring in all types of EB. They often mimic melanoma clinically, dermatoscopically, and histopathologically. The ability to recognize an EB nevus is essential for appropriate management of the patient. Unnecessary surgical excision in patients with already high-risk EB should be avoided. Close monitoring of these lesions is recommended because no cases of transformation to melanoma have been described.

We report an immunohistochemical study of eight cases of recurrent nevi. S-100 protein-positive and Factor XIIIa-negative fibroblast-like cells were found in and around the scar. Some cells were adjacent to vessels whereas others were dispersed in the fibrotic tissue. These cells probably represent entrapped or migrating nevus cells originating from the deep, unremoved portion of the nevus.