Fig. 5A(i) and resulting densitometry analysis (Fig. 5A(ii)) show that CLIC1 and CLIC4 expression is enhanced in both MCC samples compared with healthy skin. To further investigate the differential expression of CLIC proteins in the context of MCC, multicolor immunochemistry analysis was performed on formalin-fixed, paraffin-embedded (FFPE) sections of primary MCPyV-positive MCC tumors distinct from the tumor samples used above (MCC#3 and #4). Sections were incubated with antibodies specific for CLIC1 and cytokeratin 20 (CK20), a marker widely used to distinguish MCC and MCPyV LT (Fig. 5B). Here, KRT20 is linked to neoplasm.