[Histopathologic study of melanoma of the choroid after proton therapy]

To evaluate irradiation effects on choroidal melanomas, histopathologic findings of 18 eyes whose primary treatment was enucleation were compared to 15 eyes enucleated after proton beam irradiation. Irradiated tumors showed more likely necrosis (p = 0.01) had balloon cells (p = 0.01), and inflammatory infiltrate (p = 0.05). In the irradiated group, the prevalence of tumor blood vessel damage was higher (p = 0.0002) and mitotic figures were fewer (p = 0.01). These findings suggest that proton beam irradiation damages tumor cells and alters the tumor's capacity for cellular reproduction. It damages blood vessels leading to tumor necrosis. It induces an inflammatory response of unknown effects. Radiosensitivity of choroidal melanomas cannot be assessed using conventional histologic methods. However, tumor necrosis, mitotic activity and rate of balloon cells can help to establish tumoral sensitivity to irradiation.