MedicineOncologyPathologyRadiobiologyThoracic OncologyThoracic Radiation OncologyCellular Radiation ResponseRadiation Exposure In ChildhoodRadiation PneumonitisRadiation TherapyRadiation ToxicityTissue Responses To RadiationImmune Cell DepletionIonizing IrradiationIrradiation DamageIrradiation EffectsPediatric Radiation ToxicityTissue Radiation Injury
The pathology of lung changes following radiotherapy is considered with reference a case report and similar cases reported in the literature. The case presented suggests a mechanism by which the ionlzing injury produces these reactions. In a 4-yr-old child, irradiation of the mediastinum and right lung for lymphosarcoma was followed by progressive respiratory distress and death. The central tissue dose of 200-kv x rays was 2915 r. Autopsy examination revealed radiation pneumonltis of the right lung and an equally pronounced and indistinguishable reaction of the left lung. It is suggested that the bilateral reaction was due to blockage of the outflow tract for alveolar macrophages in a dynamic cell system in which cell renewal is in balance with cell depletion. It is also suggested that the critical factor in the pathogenesis of the early stage of radiation pneumonitis may be the patency of the lymph vessels that drain the lung. This interpretation differs from the conventional interpretation of the early stage in that the increased number of macrophages in the pulmonary tissue represents a proliferative response of the alveolar lining cells to radiation injury. However, pronounced proliferation of cells after high doses of x irradiation is incompatible with its prominentmore » mitosis-inhibiting effect, and the development of the reaction outside the area of exposure further indicates some mechanlsm other than a primary effect of the physical agent. (BBB)« less