beta-Catenin expression in the transitional cell zone of pilomatricoma.

BACKGROUND: beta-Catenin, a participant in the Wnt pathway, has been shown to play an important role in the morphogenesis of hair follicles and the formation of hair follicle-related tumours, including pilomatricomas. It has been observed that at least 75% of human pilomatricomas possess activating mutations in beta-catenin. These findings suggested that beta-catenin plays an important role in the tumorigenesis of pilomatricomas. However, the pattern of beta-catenin expression in pilomatricoma tissues is still unclear. Objectives To examine the expression of beta-catenin in human pilomatricomas by immunohistochemical staining. METHODS: Twenty-six formalin-fixed and paraffin-embedded samples of pilomatricoma tissue were studied. RESULTS: Most transitional cells of pilomatricoma expressed beta-catenin strongly, but the basophilic cells and shadow cells did not. beta-Catenin showed a prominent membranous immunoreactivity and a small amount of condensed cytoplasmic staining, but there was definitely no evidence of nuclear positivity. CONCLUSIONS: These findings imply that beta-catenin is primarily involved in cell-cell adhesion rather than cellular proliferation during pilomatricoma pathogenesis, and suggest that if beta-catenin is involved in pilomatricoma tumorigenesis and tumour growth, it plays an indirect role.