Nuclear localization of E-cadherin expression in Merkel cell carcinoma

Context-Cadherins are cell-cell adhesion proteins that act as tumor suppres sor genes and have a critical role in cell sorting and tissue formation dur ing organogenesis. The pattern of cadherin expression constitutes a useful diagnostic and prognostic tool in the evaluation of tumors and for determin ing the histogenesis of tumor cells. We have previously characterized the c ell types of several tumors based on the expression of individual cadherins . Objective.-To investigate the expression of cadherins in Merkel cell carcin omas. Design.-Paraffin immunohistochemical analysis of the 3 best-studied cadheri ns was performed on 35 cases of Merkel cell carcinoma. Results.-E-cadherin was expressed in 34 (97%) of 35 Merkel cell carcinomas examined, N-cadherin was expressed in 22 (63%) of 35 cases, and P-cadherin was expressed in 15 (43%) of 35 cases. This frequency of cadherin expressio n was similar to a group of smalt cell and neuroendocrine tumors from other primary sites. Interestingly, the localization of E-cadherin expression wa s unique in Merkel cell carcinomas compared with other primary neuroendocri ne tumors. Merkel cell carcinomas showed marked preference for nuclear vers us membrane localization, whereas small cell tumors from other sites showed fewer cases of nuclear E-cadherin expression. The nuclear localization of E-cadherin did not correlate with cadherin-associated protein beta-catenin nuclear expression. Conclusions.-Our findings show that E-cadherin is the most frequently expre ssed cadherin in Merkel cell carcinoma, followed in frequency by N-cadherin then P-cadherin. The pattern of nuclear E-cadherin expression is more freq uent for Merkel cell carcinoma than smalt cell tumors of other primary site s. These observations suggest that E-cadherin expression and function are a ltered in Merkel cell carcinoma, and this finding has potential use in the differential diagnosis of these tumors.