Metastatic tumors are the most common tumors of the lung in childhood. The most common metastatic solid tumors in routine pediatric surgical pathology practice are osteosarcoma and Wilms tumor (nephroblastoma), although a wide variety of sarcomas, embryonal tumors of childhood, and rarely carcinomas may metastasize to the lung. Although many biopsies of lung nodules are obtained for diagnosis and staging in pediatric oncology patients at presentation, other patients have multiple wedge excisions of metastatic nodules (metastasectomy) as part of the management of their disease. This practice is widely accepted as part of surgical oncologic management for osteosarcoma, alveolar soft-part sarcoma, and adrenocortical carcinoma, for example. Wedge excisions are uncommonly applied for other radiation-sensitive and chemotherapy-sensivity tumors, such as Wilms tumor, Ewing sarcoma, neuroblastoma, rhabdomyosarcoma, thyroid carcinoma, and germ-cell tumors.

In addition to involvement of mediastinal lymph nodes, the lung parenchyma may be secondarily involved in children with hematolymphoid malignancies, including acute lymphoblastic leukemia, acute myeloid leukemia, Burkitt lymphoma, Hodgkin lymphoma, large B-cell lymphoma, and post-transplant lymphoproliferative disorders. In contrast to adults, children with Langerhans-cell histiocytosis of the lung typically have other evidence of systemic disease, rather than isolated pulmonary involvement.