Microwave cell death: Enzyme histochemical evaluation for metastatic carcinoma of the liver.

We have reported that microwave cell death is a unique cell death preserving not only cell and nuclear shapes but also immunohistochemical antigenicity. However, their enzyme activity was lost, which indicated cell dysfunction and death. This peculiar observation implies that the microwave effect is likely an 'in situ' tissue fixation and that this type of cell death is morphologically different from cell death, by either oncosis or apoptosis, as previously known. To confirm whether this peculiar cell death was observed also in human tissue samples, we examined clinical samples from patients with metastatic liver cancer, which were treated with microwave irradiation. They were examined immunohistochemically for human Ki-67 antigen and proliferating cell nuclear antigen and enzyme histochemically for alkaline phosphatase, and the same morphological changes that were observed in microwave-treated rat liver were found. In conclusion, we believe that routine hematoxylin-eosin stain alone is not a suitable method to evaluate microwave treatment for cancer because microwave coagulation therapy-treated cells preserved their nuclei and cellular architectures, even after 3 months. For microwave-treated tumors, enzyme histochemistry is helpful to determine its effectiveness.