Beta-catenin expression in pilomatrix carcinoma with multiple visceral metastases in a dog.

Beta-catenin is a protein initially identified as a submembrane component of the E-cadherin-mediated cell-to-cell adhesion system. It plays a role as a transcriptional factor in the wingless/Wnt signalling pathway. Beta-catenin has been associated with oncogenic activity in human benign and malignant pilomatrix neoplasms where the immunohistochemical profile of β-catenin expression displayed both nuclear and cytoplasmic staining in basaloid cells. In this study, an 8-year-old female Irish setter dog was examined because of the presence of skin nodules. Tissue biopsies from different nodules were obtained and histological examination suggested a diagnosis of pilomatrix carcinoma. The dog spontaneously died after 2 months and necropsy showed multiple metastases in the nasal cavity, lungs, heart, kidney, liver and colon. Routine histopathology of metastatic sites showed features consistent with the pattern of primary neoplastic nodules. Immunohistochemical detection of β-catenin was performed in both the primary tumour and the metastases. Beta-catenin expression was located in the nuclei, cytoplasm and membrane of squamoid cells and in the cytoplasm of basaloid cells, while shadow cells were completely negative. To the best of our knowledge, these data represent the first report on the immunohistochemical expression profile of β-catenin in canine pilomatrix carcinoma.