Malignant tumors of the head-and-neck region with a long latent interval after radiotherapy

29 cases of malignant tumors of the head-and-neck region with a long latent interval after radiotherapy for cancers were analyzed clinico-pathologically in order to determine if any cancers were radiation-induced. Moreover, they were compared with 11 other cases whose initial lesions were benign. Among cases with malignant initial lesions, some were suspected to be radiation-induced, if their latent intervals were longer than 17 years. Through case analysis of each malignancy, however, most of these malignancies were considered not radiation-induced but recurrent, except for cases whose initial lesions were not malignant. (auth.)