Introduction: Connexins (Cxs) are channel proteins that allow direct connection among cells and between cells and the extracellular space. There is very little information in the literature on the expression of Cxs by Merkel cell carcinoma (MCC).
Materials and methods: Thirty-two cases of MCC were recovered from our archives and studied immunohistochemically for Cx43.
Results: All our cases expressed several neuroendocrine markers. Most cases showed nonimmunohistochemically perceptible staining for Cx43. There was no difference between Merkel cell polyomavirus (MCPyV)-positive and MCPyV-negative cases. One case could not be evaluated. Only 2 cases showed a focal (10% of the tumor) membranous staining of Cx43. One of these cases was MCPyV-negative and, in the other, CM2B4 could not be evaluated. CM2B4 was positive in 18 cases and negative in 13 cases, and it could not be evaluated in 1 case.
Conclusions: MCC shows a low Cx43 level, with no differences between MCPyV-positive and MCPyV-negative cases. Therefore, this opens the door for Cx43 targeting in therapeutic approaches to MCC.