Sonographic features of sternal pseudotumour in children.

Introduction: Sternal pseudotumour is an important but rare entity thought to be an inflammatory, non-neoplastic lesion that can mimic tumours. The purpose of this paper was to illustrate the imaging features of this lesion to avoid unnecessary investigations. Methods: The clinical notes and imaging features of four patients with a diagnosis of sternal pseudotumour were reviewed over a period from February 2016 to July 2019. Results: All patients were afebrile with no history of trauma. The median age at presentation was 12.5 months. The median length of symptoms prior to presentation was 3.5 days. One patient had a mildly elevated C-reactive protein. Chest radiographs showed a pre-sternal soft-tissue mass, with or without osseous destruction of the subjacent sternum. Ultrasound showed a heterogeneous, hypoechoic pre-sternal soft-tissue mass with variable internal vascularity with extension between sternal ossification centres. CT and MRI showed an enhancing dumbbell-shaped lesion with a pre-sternal and retro-sternal soft-tissue component. The median time to complete resolution was 3 months. One patient had a biopsy that showed chronic inflammation and fibrosis. Discussion: These lesions present in young children typically with a 1- to 2-week history of a focal 2- to 4-cm swelling over the sternum. The aetiology is unknown but may be on the basis of a yet-to-be identified pathogen. Inflammatory markers and cultures are normal or mildly elevated. Important differential considerations include sternal osteomyelitis or neoplastic causes such as Ewing sarcoma, rhabdomyosarcoma, Langerhans cell histiocytosis and infantile fibrosarcoma. Conclusion: Sternal pseudotumor is a rare but important entity to be aware of to avoid unnecessary invasive biopsy or further investigations. Our suggestion is that this is a 'Don't touch' lesion that requires close short-interval follow-up at a surgical outpatient clinic and with ultrasound until resolution.