A case of basaloid‐squamous carcinoma of the esophagus: Immunohistochemical and ultrastructural studies

A case of basaloid-squamous carcinoma of the esophagus in an 83 year old man is reported. The esophageal tumor showed a fungating growth at the junction of the middle and lower esophagus and was composed microscopically of submucosal multiple nests with solid and cribriform-like patterns accompanied with a small focus of squamous cell carcinoma adjacent to the overlying esophageal epithelium. The structural features closely resembled those of basaloid-squamous carcinoma. The submucosal tumor cells were immunohistochemically positive for epithelial membrane antigen, wide spectral keratin, alpha actin and S-100 protein. By electron microscopy, the tumor cells had microvilli, desmosomes and bundles of myofilaments, and replicated basement membranes were frequently observed adjacent to the nests. The positive immunoreaction of S-100 protein and alpha actin and the existence of bundles of myofilaments indicated that the present tumor did not correspond well with basaloid-squamous carcinoma. In addition, there was no evidence of true glandular lumina in the tumor nests, a finding which was inconsistent with that of adenoid cystic carcinoma. From the immunoreactivity of S-100 protein and ultrastructural features, it was considered that the present submucosal tumor had originated from undifferentiated pluripotential primitive cells, which differentiated to myoepithelial cells.