Small cell carcinoma of the esophagus.

Ten cases of small cell carcinoma of the esophagus were studied clinicopathologically and immunohistochemically. Seven of the ten were also examined by electron microscopy. Histologically, six were oat cell type, four the intermediate cell type, and multiple histologic sections revealed squamous and glandular differentiations in small or minute areas of seven and two tumors, respectively. In four of the six polypoid tumors, the epithelium covering the tumor showed a malignant conversion accompanied by a proliferation of small anaplastic cells. Another one showed a cribriform pattern in a small area of the tumor. Argyrophilic tumor cells were seen in six cases and tumor cells immunohistochemically positive for ACTH and calcitonin were seen in six, and three cases, respectively. Neurosecretory granules were evident in three of the seven cases examined by electron microscopy. These findings suggest that a small cell carcinoma of the esophagus differentiates toward a squamous, glandular, or neurosecretory lesion, thereby supporting the idea of a totipotential stem cell origin of this tumor. The prognosis of patients with this tumor was poor, in accord with the evidence of aggressive lymphatic and blood vessel permeation.