Oat cell carcinoma or undifferentiated carcinoma arising from esophagus is very rare. Some authors have described this tumor and its cytological characteristics.
We report an autopsy case of esophageal oat cell charcinoma (undifferentiated carcinoma). We found the caracteristic cancer cells in pleural fluid in the case who was resected esophagus partially for esophageal carcinoma.
We reviewed these cancer cells, and compared them with cancer cells in pleural fluid from a case of bronchial oat cell carcinoma. Cytological characteristics of this case were as follows;
1) They are small and are arranged as mosaic pattern.
2) They are slightly larger than cancer cells from a case of bronchial oat cell carcinoma.
3) Nuclei are polygonal or round in shape, and they are less irregularly shaped than those of bronchial oat cell carcinoma.
4) Nuclear membranes are thin, and chromatin is finely granular and is distributed evenly.
5) Nucleoli are small, and not conspicuous.
Histologically, they were negative for argyrophil reaction by Grimelius stain or Bodian stain. They were also negative for argentaffin reaction by Fontana-Masson stain. By electronmicroscopy we detected a small number of neurosecretory granules.