Recurrent Nevi and Nevi with Sclerosing Features and Inflammation

Recurrent nevi are benign melanocytic nevi that regrow after incomplete surgical removal or traumatic injury. Recurrent nevi are biologically benign without a documented risk of malignant progression, but they pose diagnostic problems because their morphological features resemble those of melanoma. They are also commonly referred to as “pseudomelanomas.” The management of repigmentation within a scar after incomplete biopsy or other destructive procedures (i.e., laser and cryotherapy) depends on whether a prior histopathologic diagnosis confirming a benign tumor was obtained or not. In cases of regrowth without histopathologic diagnosis, immediate excision and histopathologic examination are mandatory to rule out melanoma unintentionally treated as benign tumor. When a prior histopathologic diagnosis reports a benign tumor, often no further interventions are performed. However, careful histologic reevaluation of the slides of the previous excision is strongly encouraged, in order to avoid a misclassification which potentially delays diagnosis and adequate treatment of recurrent melanoma. The differential diagnosis of newly developing pigmentation within a scar of a previous excision of a melanocytic lesion includes recurrent nevus, recurrent melanoma, and melanotic reactive pigmentation. As a general rule, a relatively rapid development of the repigmentation favors the diagnosis of a benign recurrence. This is confined within the scar, and, dermoscopically, a regularly pigmented network and thin parallel streaks are associated with reactive pigmentations, whereas an irregular prominent network, globules, streaks, and heterogeneous pigmentation are usually associated with a melanocytic proliferation. On the other side, melanomas tend to recur months if not years after excision at the edges of the scar in the normal skin. Dermoscopy may not reveal specific melanoma features, displaying only a heterogeneous, structureless pigmentation. Therefore, in the case of a recurrent pigmentation involving the normal skin around the scar, a biopsy specimen should be obtained to exclude a possible melanoma recurrence. Histological features, even in case of recurrent nevi, can be very worrisome as recurrent nevi generally present a rich junctional component, sometimes frankly atypical and, with epidermotropism, arising on a sclerotic dermis.