Atypical pulmonary metastases in children: pictorial review of imaging patterns.

Pulmonary metastases typically present as well-circumscribed solid nodules, often with a basilar and peripheral distribution due to hematogenous spread. When an atypical pattern of metastasis occurs, a lack of recognition may result in understaging or a delay in diagnosis. The purpose of this article is to review the imaging findings of atypical pulmonary metastatic disease in children. Atypical pulmonary metastatic patterns that can be seen in children include cavitary lesions, calcified pulmonary nodules, nodules with peritumoral halos, tree-in-bud or strial pattern secondary to tumor in peripheral pulmonary arterial branches, lymphangitic carcinomatosis, and miliary disease. An awareness of the spectrum of imaging findings of atypical pulmonary metastases along with an understanding of histopathological underpinnings will allow the radiologist to make an accurate diagnosis.