Ultrastructural effects of irradiation on squamous cell carcinoma of the head and neck.

Tissue samples taken before and during the radical irradiation of the squamous cell carcinoma of the head and neck region were studied by light and electron microscopic examination. Radiation-induced cellular changes of which nuclear atypia was most pronounced. The tumor invasion pattern remained unchanged but the number of mitoses decreased. The lymphocytic infiltration increased at the beginning of the therapy (from 10-30 Gy) but decreased at the end of radiotherapy. The amount of neutrofils and the keratinization pattern remained almost unchanged at the light microscopic level, but intracellular filaments and desmosomes slightly increased in electron microscopic study. The changes in nuclear morphologic features pointing in a more undifferentiated direction are considered to be due to cell damage rather than to the more aggressive behavior of the tumor cells. This is in agreement with the decrease of mitoses which is due to radiation-induced arrest of tumor cells to the G2 phase. These changes might be related to the disappearance of tumors during irradiation. The leukocyte compartment seen in the samples might take part in the destruction of the tumor cells and in the removal of the cell debris.