Osteoma Cutis Arising in Common Blue Nevus (Blue Osteonevus): A Clinicopathologic, Immunohistochemical, and Dermoscopic Study.

Osteonevus of Nanta is a rare histopathologic variant of melanocytic nevus that results from ossification of the dermis between dermal nests of melanocytes. Most cases described in the literature have been associated with long-standing intradermal nevi and were often located in the upper part of the body. We report a lesion on the shoulder of an elderly man showing the association of a common blue nevus and osteoma cutis, an exceptional feature which has been previously reported in 2 instances. We also describe for the first time the dermoscopic appearance of this "blue osteonevus."