Purpose or Case Report: Pulmonary metastases typically present as well-circumscribed, solid nodules of variable size in most pediatric malignancies. Hematogeneous metastases tend to have a basilar and peripheral predilection. Atypical patterns of pulmonary metastases can however occur and lack of recognition can result in understaging or delay in diagnosis. The purpose of this poster is to review the imaging findings of atypical pulmonary metastatic disease in children. Cases from two large tertiary care institutions will be used for illustration.
Atypical pulmonary metastatic patterns include: 1. Dilated and beaded peripheral pulmonary vessels secondary to intravascular metastatic disease (e.g. osteosarcoma). Though central tumor embolus or tumor thrombus is easy to recognize, certain tumors such as osteosarcoma can cause intravascular metastatic disease in peripheral pulmonary arteries which has a characteristic imaging appearance and can mimic a "tree-in-bud" pattern. 2. Interstial thickening secondary to lymphangitic spread of tumor (e.g. lymphoma, renal medullary carcinoma, adenocarcinomas in children). This can be seen with or without mediastinal lymphadenopathy and is characterized by nodular septal line thickening. 3. Miliary pulmonary nodules (e.g. papillary thyroid cancer). Papillary thyroid carcinoma, the most common pediatric thyroid malignancy, can present with innumerable tiny pulmonary nodules which maybe mistaken for an infectious etiology secondary to indolent course. 4. Cavitary pulmonary masses (e.g. sarcomas). Cavitary nodules maybe seen at presentation in certain sarcomas or as a consequence of therapy induced central necrosis. 5. Calcified nodules (e.g. osteosarcomas) which can be mistaken for granulomas. 6. Nodules from hypervascular tumors can show hemorrhagic halos (e.g. angiosarcoma, choriocarcinomas). 7. Endobronchial metastasis can present with persistent segmental/lobar collapse.
An awareness of the spectrum of imaging findings of atypical pulmonary metastases along with their histopathologic correlates will allow the radiologist to make an accurate diagnosis.
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