Exocrine and endocrine cell differentiation in small intestinal adenocarcinomas

Sixteen adenocarcinomas of the small intestine were examined with respect to the ability of the the tumour cells to differentiate in exocrine and endocrine directions. Both intra- and extracellular mucous material was found in 14 tumors and lysozyme immunoreactivity, a characteristic of normal Paneth cells, was seen in scattered tumor cells in two cases. Three tumors contained a few argyrophil cells, indicating the presence of tumor cell population with endocrine production. In two of these tumors some tumor cells displaying an argentaffin reaction, a staining property characteristic of enterochromaffin cells storing serotonin, were also found. In one tumor examined electron microscopically, tumor cells with cytoplasmic zymogen granules were seen and also two different types of endocrine tumor cells containing neurosecretory hormone granules. The results show that the tumor cells of small-intestinal adenocarcinomas possess the ability to differentiate in both the exocrine and the endocrine direction.