Nuclear β-catenin immunoexpression in scars.

BACKGROUND Histopathologically, scars can mimic superficial fibromatoses. Superficial fibromatoses are known to show nuclear β-catenin immunoexpression, although the tumor types do not harbor CTNNB1 or APC alterations. The present study aimed to evaluate nuclear β-catenin immunoexpression in scars compared to that in superficial fibromatoses. METHODS Immunostaining with an anti-β-catenin antibody, clone 14, was performed on 8 superficial fibromatoses and 22 scars. The extent of β-catenin nuclear staining was classified as negative (<10%), focally positive (10-49%), or diffusely positive (50-100%). β-catenin staining intensity was semi-quantitatively graded as weak, moderate, or strong. RESULTS In 21 (95%) scars, nuclear β-catenin immunoexpression was detected in fibroblasts/myofibroblasts, with mainly diffuse (16/21) and moderate (14/21) to strong (4/20) staining. In contrast, seven (88%) of the eight superficial fibromatoses expressed β-catenin in the nuclei of the lesional spindle cells, at varying levels of staining intensity. Fibroblasts in normal papillary dermis always showed nuclear β-catenin expression to varying degrees but those in the reticular dermis did not. CONCLUSIONS Scars typically exhibit nuclear β-catenin expression similar to that in superficial fibromatoses. Thus, β-catenin immunohistochemistry is not suitable for distinguishing superficial fibromatoses from scars. This article is protected by copyright. All rights reserved.