Expression of cadherin/catenin cell--cell adhesion molecules in a onychomatricoma.

Onychomatricoma is a rare nail tumor with a distinctive architecture. Proximally, there are serum-filled invaginations of nail matrix epithelium into the stroma, and distally, dermal protrusions perforate the nail plate. Because other matrical tumors of follicular and odontogenic origin express nuclear beta-catenin, we examined the expression of cadherin/catenin proteins in this onychomatricoma case. The patient presented with a toenail yellow streak, and the biopsy revealed an onychomatricoma. E-cadherin and beta-catenin were at the cell membrane in the epithelial invaginations. P-cadherin was restricted to basal cells. In contrast to other matrical tumors, nuclear beta-catenin was not present. These results suggest that onychomatricoma may lack the transcriptional activating role of beta-catenin that characterizes follicular and odontogenic matrical tumors. This is the first report on the expression of cadherin/ catenin cell-cell adhesion proteins in this rare nail tumor.