Many varieties of tumors occur in the thoracic region of children. Some are of congenital origin; other primary neoplasms develop as childhood advances, and some are metastatic. The following entities are illustrated in this exhibit: Group I: Primary tumors: malignant: bronchogenic carcinoma, mesothelioma, leiomysarcoma, angioendothelioma, neuroblastoma, and Ewing's sarcoma; benign: hygroma, enlarged thymus, teratoma, thyroid adenoma, lung cyst, hemangioma, neurofibromatosis, and neuroma. Group II: Metastatic tumors: neuroblastoma, Wilms' tumor, Ewing's sarcoma, osteogenic sarcoma, and rhabdomyosarcoma. Group III: Lymphomas: lymphosarcoma, leukemia, and Hodgkin's disease.