Purpose or Case Report: In this pictorial essay on typical and atypical lung metastases in pediatric patients, we aim to assist radiologists in identifying suspicious features on CT scans. Our goal is to guide decisions regarding follow-up imaging to ensure a timely diagnosis, enabling children to receive prompt and potentially lifesaving treatment.
Methods & Materials: Pediatric pulmonary nodules are rare and present a diagnostic challenge when found incidentally in healthy children or as atypical metastases in oncologic patients. Chest computed tomography (CT) is the primary imaging modality for assessing lung nodules. In the pediatric population, Wilms tumor and osteosarcoma are the cancers most likely to produce pulmonary metastases, both typical and atypical. This essay will provide a comprehensive understanding of the specific radiological features of atypical pediatric pulmonary metastases, their pathogenesis, and their differential diagnosis. We will address diagnostic approaches to incidental lung nodules in healthy children as found in current literature.
Results:
Fleischner guidelines evaluate incidental lung nodules in adults for cancer risk, but there's no equivalent for children. In asymptomatic kids, solid nodules with benign features like fat content, uniform calcification, and stability over time are low-risk and need no follow-up.

For pediatric lung metastases, Wilms tumor and osteosarcoma are leading causes. CT reveals patterns based on cancer spread: hematogenous spread shows well-defined nodules in lower lobes, while lymphatic spread results in reticular or miliary patterns.

Atypical metastases can appear as cavitating, cystic, calcified or bleeding nodules, and may result in pneumothorax or endobronchial involvement. Tumor emboli have three forms: large artery emboli, small and medium artery metastases, and pulmonary tumor thrombotic microangiopathy.
Conclusions: A risk-based approach to incidental findings of single lung nodules in healthy children is crucial, informed by available data. This pictorial essay suggests such an approach, emphasizing current risk-based strategies and diagnostic guidance for pediatric radiologists, and providing insights into the pathogenesis and differential diagnosis of atypical pediatric pulmonary metastases.