Bone formation within the skin may be a primary or secondary phenomenon. Primary cutaneous ossi­fication can occur in Albright’s hereditary osteo­dystrophy and as primary osteoma cutis. Secondary metaplastic ossification occurs in association with a wide variety of conditions, including pilomatricoma, basal cell carcinoma, acne, melanocytic nevi, cel­lular blue nevus, scar, cutaneous mixed tumor, cylindroma, a cutaneous nodule of mixed connective tissue disease, dermatofibroma, ossifying plexiform tumor, pyogenic granuloma, cutis laxa-like pseudo- xanthoma elasticum, congenital plate-like osteoma cutis, organoid nevi, epidermal cyst and at the site of trauma or injection. The melanocytic nevus with secondary ossification is referred to as ‘nevus of Nanta. Melanocytic nevus with bone was first described by Heidingsfeld in 1908. Ever since Nanta reported on it in detail in 1911, it has been called osteo-nevus of Nanta. The histopathology of nevus of Nanta is characterized as ossification within or just beneath the nevus cell nests.

To the best of our knowledge, the nevus of Nanta has not been reported on in the Korean medical literature, but there have been reports of large series in the international literature. Both Conlin et al and Moulin et al reported that the nevus of Nanta was the most frequent cause of secondary ossifica­tion of the skin. The occurrence of nevus of Nanta was variable between 1.4% to 26% of all cutane­ous ossifications.

The origin of the ossification within the melano- cytic nevus is not precisely known. Many different theories have been proposed to explain this somewhat unusual finding. Burgdorf and Nasemann have suggested two mechanisms by which cutaneous ossification may occur: 1) transformation of primi­tive mesenchymal cells into osteoblasts that produce bone or 2) metaplastic transformation of other undetermined dermal cells that’s stimulated by the appropriate cellular milieu. Keida et al suggested the involvement of transforming growth factor- в and connective tissue growth factor in the ossifi­cation of nevus of Nanta. Conlin et al reported that women were more commonly affected than men and they hypothesized there was an estrogenic effect on osteoblasts. Yet the exact reason why osteoma formation occurs remains to be determined. Apcalis Oral Jelly

In our case, the patient denied any preceding inflammation or trauma on the nevus, but it is difficult to exclude the possibility of previously un¬recognized trauma or inflammation. We recom¬mended getting an operation because there has been a reported case of malignant melanoma arising in a nevus of Nanta, but the patient refused.