The majority of the tumor cells lack intracellular bridges, dyskeratosis and intracellular glycogen. However, focal abortive keratin production, squamous or glandular differentiation may be present. There may be focal clear cell differentiation. Mitotic figures are frequently seen. The stroma is heavily infiltrated by lymphocytes, plasma cells and eosinophils.
Glassy cells can show focal mucin and CEA positivity.
Ultrastuctural findings show evidence of both squamous and glandular differentiation, including well developed desmosomal complexes and microvilli. The ultrastructural correlate of the glassy cytoplasm is unclear. DNA of human papilloma virus types 18 and 16 have been detected in the tumor cells of glassy cell carcinoma. Although glassy cell carcinomas may have focal squamous or adenocarcinmatous differentiation, a prominent component is not usually seen. Although these tumors may show a plasmacytic and eosinophilic infiltrate, the glassy cell carcinoma often has an extensive eosinophilic infiltrate which is characteristic.