Agminated atypical melanocytic nevus associated with Langerhans cell histiocytosis.

Agminated nevus refers to the presence of multiple nevi grouped in a circumscribed skin area; it is rarely reported in the literature. This report presents the case of a 10-year-old female patient with a history of Langerhans cell histiocytosis, who presents multiple nevi in the lumbar and inguinal region. In the histopathological study, an atypical melanocytic nevus was reported. Wood's lamp examination discarded the presence of nevus spilus, and the diagnosis of agminated nevus was reached. The association of this type of nevus with Langerhans cell histiocytosis is rare, and only four cases were found reported in the indexed literature. The reason for this association is unknown, thus a new theory about its origin is presented here.