E-cadherin loss rather than β-catenin alterations is a common feature of poorly differentiated thyroid carcinomas

Aims: To investigate the immunohistochemical and molecular genetic features of the cadherins/catenins complex in thyroid carcinoma based on the hypothesis that poorly differentiated carcinoma of the thyroid represents an intermediate step between well‐differentiated and undifferentiated carcinomas. Methods and results: Immunohistochemistry for E‐, P‐ and N‐cadherins and α‐, β‐ and γ‐catenins was performed in a series of 17 cases of poorly differentiated carcinoma of the thyroid. All cases showed absence of membranous expression of E‐cadherin with no aberrant expression of P‐ or N‐cadherins; regarding catenins there was heterogeneous loss of expression with membranous immunolocalization of the three catenins in most cases. Molecular analysis of the E‐cadherin gene and exon 3 of the β‐catenin gene was also performed by polymerase chain reaction/single‐strand conformation polymorphism and sequencing. No mutations in either gene were detected in any case. Conclusions: In contrast to previous reports, our results suggest that loss of E‐cadherin rather than β‐catenin mutation is the crucial event in determining the differentiation ‘level’ of thyroid carcinomas.