Epithelial Elements in Superficial Angiomyxomas: Mimicry of Adnexal Development and Mesenchymal-To-Epithelial Transition

This study investigated the nature of epithelial elements in 43 superficial angiomyxomas, including one from a Carney's complex patient, to determine if they are trapped adnexal epithelium, outgrowths triggered by myxoid tumor cells, or genuinely neoplastic. The findings revealed that adnexal epithelial elements mimic their embryogenesis through S100A4-positive mesenchymal niches near myxoid cells with PRKAR1A loss, suggesting non-neoplastic growth induction. In the Carney's complex case, mesenchymal-to-epithelial transition was observed in eccrine duct branching, likely due to protein kinase A activation. This indicates that complex epithelial structures retain PRKAR1A, differentiating them from the induced non-neoplastic growth.