Expression Patterns of Hair and Epithelial Keratins and Transcription Factors HOXC13, LEF1, and β-Catenin in a Malignant Pilomatricoma: A Histological and Immunohistochemical Study

The study investigated a malignant pilomatricoma, focusing on the expression patterns of hair and epithelial keratins and transcription factors. It found that the malignant tumor maintained hHa5/HOXC13 co-expression and disrupted hHa1/β-catenin–LEF1 expression in its transitional cell compartment, similar to benign pilomatricomas. However, unlike benign tumors, the malignant pilomatricoma's transitional cells also strongly expressed epithelial keratins K5, K14, and K17. This expression pattern suggested a dominance of the epithelial differentiation pathway, which might prevent the tumor's calcification.