Skin Tumors With Matrical Differentiation: Lessons From Hair Keratins, Beta-Catenin and PHLDA1 Expression

The study investigated 36 matrical tumors, excluding pilomatricomas, to understand their differentiation and molecular characteristics. It found that these tumors exhibited cortical differentiation with sequential expression of K35, HOXC13, and K31 keratins. Nuclear accumulation of beta-catenin and expression of LEF1 and PHLDA1 were consistently observed, indicating a common tumorigenesis pathway driven by Wnt pathway activation. The findings suggested that PHLDA1 expression is a marker for matrical differentiation in these tumors.