Pulmonary adenosquamous carcinomas with amyloid-like stroma

Two unique cases of pulmonary carcinomas showing squamous and glandular differentiation and the production of excessive amounts of extracellular waxy eosinophilic material resembling amyloid are reported. Immunohistochemical studies showed strong staining of the neoplastic cells with antibodies directed at cytokeratin, epithelial membrane antigen, and carcinoembryonic antigen. Of particular interest was the simultaneous strong staining for S-100 protein and vimentin. The histology, ultrastructure, and immunohistochemical findings suggest focal myoepithelial differentiation in these mixed carcinomas and indicate an analogy to salivary gland neoplasms, particularly adenoid cystic carcinoma and dermal analog tumors.