The paranuclear dot in Merkel cell carcinoma, how does it form and what does it do?

Background and aims: Staining for Cytokeratin 20 (CK20) and other intermediate filaments in a paranuclear dot pattern is a histological feature used to diagnose the neuroendocrine skin cancer Merkel cell carcinoma (MCC). The functional significance of these paranuclear protein aggregates is unknown. Therefore, we sought to investigate the structure and function of the paranuclear dot in MCC. Methods: In native tumors and MCC cell lines we used: immunostaning, microscopy, chemical inhibition, siRNA knockdown, and cell death modulators to study the paranuclear dot.