Thus, we characterized fibroblasts in the MCC microenvironment by evaluating the expression of other fibroblast markers such as TE-7, Caveolin-1 (CAV1), α-SMA, and S100A4, using multiplex immunohistochemistry (mIHC) staining (n = 10, Supplementary Tables S1 and S2, example results shown in Fig. 1a and Supplementary Fig. S1). Here, S100A4 is linked to Merkel cell skin cancer.