The aim of this study was to investigate
serotonin and
bombesin expression in colorectal
adenocarcinomas and neuroendocrine
colorectal tumors to clarify their role in the progression of
colon cancer. The investigation was carried out by electron microscope immunocytochemistry. The ultrastructural study revealed that some cases of colorectal
adenocarcinomas were characterized by the presence of amphicrine cells containing endocrine granules and mucus granules. Poorly differentiated
adenocarcinomas and liver
metastases were poorly granulated compared with highly differentiated
tumors.
Neuroendocrine tumors nevertheless were characterized by the presence of numerous malignant neuroendocrine cells filled with secretory granules and mucus granules.
Bombesin appeared to be located in enterochromaffin-like endocrine cells, which are primarily responsible for the production of
serotonin. In colorectal
adenocarcinomas there was an inverse correlation between
serotonin levels and the degree of differentiation. High
serotonin levels characterized colorectal
adenocarcinomas with composite phenotype and colorectal
neuroendocrine tumors. Increased
bombesin expression was correlated with colorectal
adenocarcinomas exhibiting poor histological grade and their liver
metastases. In conclusion, the findings suggest that high
serotonin levels may be an
indicator of neuroendocrine differentiation, and
bombesin may be a useful marker for colorectal
adenocarcinomas with aggressive behavior,