Immunohistochemical expression of bone morphogenetic protein-2 in pilomatricoma.

Abstract

The mechanism of occurrence of calcification and ossification in pilomatricoma remains unclear. To elucidate the pathogenesis of calcification and ossification in pilomatricoma we examined the role of bone morphogenetic protein (BMP)-2, which plays important parts in inducing ectopic bone formation both in vivo and in vitro. Twenty cases of pilomatricoma were studied immunohistochemically using anti-BMP-2 monoclonal antibody. In normal skin, including hair follicles, there was no BMP-2 expression. In all pilomatricomas, BMP-2 was found exclusively in the cytoplasm of shadow cells but not in basophilic cells. In two cases of bone formation seen in pilomatricoma, osteoblasts in the periosteal area showed a strong positive reaction, while bone trabeculum (bone matrix) showed no reaction. Our findings indicate that shadow cells positive for BMP-2 may play an important part in generating bone formation in pilomatricoma.