E-cadherin in solid pseudopapillary tumors of the pancreas.

CONTEXT Solid pseudopapillary tumors of the pancreas are rare and have recently been shown to harbor mutations of the beta-catenin gene with resultant nuclear localization of beta-catenin protein to the nucleus. Moreover, there is a close relationship between beta-catenin and E-cadherin. OBJECTIVE To explore the protein expression of E-cadherin in a series of solid pseudopapillary tumors of the pancreas. PARTICIPANTS Eighteen cases of solid pseudopapillary tumors of the pancreas. DESIGN The cases were studied using a tissue microarray that was constructed as follows: for each case, 4 to 14 cores measuring 1.0 mm each were drilled from the blocks. Tissue cores from normal pancreas were used as controls and for orientation purposes. MAIN OUTCOME MEASURES The slides were stained with the following commercially available antibodies: CD10, CD56, vimentin, alpha-1-antitrypsin, alpha-1-antichymotrypsin, neuron-specific enolase, chromogranin, synaptophysin, beta-catenin and E-cadherin. RESULTS All the tumors were CD10, vimentin, alpha-1-antitrypsin and alpha-1-antichymotrypsin diffusely positive (50% or more of the tumor cells staining) and CD56 showed focal positivity in all cases with 5-10% of tumor cells displaying immunolabeling. All cases were negative for chromogranin and synaptophysin. All 18 cases displayed cytoplasmic and nuclear localization of beta-catenin protein. Similarly, E-cadherin protein was localized to the nucleus in all 18 cases, with loss of the characteristic membranous decoration of cells. CONCLUSION This study is the first demonstration of aberrant nuclear localization of E-cadherin protein in solid pseudopapillary tumors of the pancreas. Whilst the exact mechanism is not know and nuclear E-cadherin is not related to tumor aggression, this staining pattern may be of diagnostic value in concert with beta-catenin staining.