[A case of radiation-induced mucoepidermoid carcinoma of the lung following radiotherapy for pulmonary metastasis of Wilms' tumor].

Radiotherapy is one of the main therapeutic methods for malignant tumors, but on the other hand it can also induce new malignant tumors. Recently, we experienced a case of a 22-year-old woman with triple cancers (Wilms' tumor, thyroid cancer and mucoepidermoid carcinoma of the lung). She had been treated repeatedly for right-sided pulmonary metastases from the Wilms' tumor. The last cancer arose from a different organ in the field irradiated to treat the first cancer, after a latent period of about 20 years. Therefore, this case is classified as highly probable radiation-induced cancer (A-1 group) by the diagnostic criteria for radiation-induced cancer proposed by Sakai et al. Second cancers (radiation-induced cancers) mainly consist of soft tissue sarcomas, leukemias, skin cancers, urinary bladder cancers, large bowel cancers and other tumors. The occurrence of mucoepidermoid carcinoma of the lung as a radiation-induced tumor had not been reported. This patient also showed poor growth of the right breast and marked deformity of the right side of the thorax as late damage from irradiation. We must make efforts to decrease late damage from radiotherapy for pediatric cancers.