Absence of E-cadherin in invasive "ductal" carcinoma (case 1). A: Moderately differentiated invasive ductal carcinoma. Focally, tumor cells are seen growing in a linear fashion and contain intracytoplasmic mucin vacuoles (inset) (Hematoxylin and eosin). B: Invasive ductal carcinoma exhibiting complete absence of reactivity for E-cadherin. Normal duct serves as an internal positive control (Immunoperoxidase stain for E-cadherin). C: Metastatic carcinoma with glandular differentiation (Hematoxylin and eosin, left) showing complete absence of E-cadherin immunoreactivity (Immunoperoxidase stain for E-cadherin, right).