Cell adhesion protein expression in melanocytic matricoma.

Melanocytic matricoma is a rare neoplasm thought to recapitulate the hair follicle in anagen. The tumor forms a nodule in the dermis containing basaloid, intermediate and shadow cells admixed with pigmented melanocytes dispersed as single dendritic cells. Because cadherins and catenins are crucial in the development of hair tumors, we examined the expression of E(epithelial)-, P(placental)-, N(nerve)-cadherin and beta-catenin in a melanocytic matricoma. A 66-year-old Caucasian woman with a history of breast cancer presented with a pigmented nodule on the shoulder. Pathology revealed a melanocytic matricoma with S-100 and HMB45-positive melanocytes. E- and P-cadherin were localized at the cell membrane of basaloid and differentiating keratinocytes, and in melanocytes, recapitulating the anagen hair. Both cadherins were absent in shadow cells. N-cadherin was not expressed. Beta-catenin had a differential distribution, in the nucleus and cytoplasm of basaloid cells, but at the cell membrane in differentiating cells and negative in shadow cells, paralleling the expression of E- and P-cadherin. Our results support the previously hypothesized resemblance of the tumor to the hair bulb in anagen and suggest a transcriptional role of beta-catenin in the development of this rare neoplasm.