• 25
    Jan
  • A Case of Nevus of Nanta: DISCUSSION

Ossification of the skin occurs in various lesions. There are two major forms of cutaneous ossification. Primary cutaneous osteoma is a primary tumor without a preceding cutaneous lesion. And secon­dary ossification, that is secondary osteoma cutis, has preexisting lesions, such as pilomatricoma, basal cell carcinoma, acne, melanocytic nevi, cellular blue nevus, epidermal cyst, or malignant melanoma.

Melanocytic nevus with bone was described first by Heidingsfeld in 1908. Since Nanta reported it in detail in 1911, it has been called osteo-nevus of Nanta. In the large series of reports in international literature, the most common cause of secondary osteoma cutis was melanocytic nevus. Most cases of nevus of Nanta occurred on the face or head, and women are more commonly affected than men. Faces are easily stimulated by such things as trauma or infection and are abundant in follicles, and nevi on faces may be of more concern for cosmetic reasons. Intradermal nevus are most common and ossification was localized to the lower.
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The mechanism of secondary ossification has not been clarified. Sasaki et al proposed two possible ossifying mechanisms in the nevus cell nevus. First, ossification may be induced by hamartomatous proliferation on embryonic germ cells. Second, ossification may be induced by the differentiation of examined the positive staining of nevus cells for transforming growth factor beta (TGF-Д) and connective tissue growth factor (CTGF) in the tissue from the nevus of Nanta, and suggested the involvement of these growth factors. Conlin et al reviewed 74 cases of osteoma, and identified 15 cases of nevus of Nanta among them. 13 of 15 cases occurred in female patients, so they speculated that a higher incidence in women may be related to estrogenic effect on osteoblasts. Moulin et al studied 125 cases of nevus of Nanta, and observed that all nevi contained hair follicles. It is likely that folliculitis by trauma or neoplastic proliferation, stimulates dermal fibroblasts and, given some appropriate stimulation, these indigenous fibroblasts differentiate into osteoblasts. Although there are several hypotheses, the exact pathogenesis is currently unclear. So further additional studies would be needed to prove these hypotheses.

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