Acute Respiratory Failure With a Rare, Rapidly Progressing Pediatric Desmoid Tumor Anterior Mediastinal Mass.

We present an unusual case of a 6-year-old boy who presented with the sudden presence of left neck mass and acute hypoxemic respiratory failure, whose subsequent imaging demonstrated a previously undiagnosed anterior mediastinal mass (AMM) extending into the left neck. Biopsy of the mass was consistent with a desmoid tumor, which is a rare cause of AMM in children. Desmoid tumors are locally aggressive, often invading and enveloping surrounding tissues, but overall slow growing. The sudden growth of the neck mass suggests a very aggressive desmoid tumor, causing an unexpected respiratory compromise. Anterior mediastinal masses may cause symptoms by compressing the heart, great vessels, and airways. However, the patient may adapt and develop compensatory mechanisms to counter the compressive effects. Emergency care of the patient with an AMM who presents with acute respiratory distress includes optimizing oxygenation through promoting a calm environment, oxygenating while minimizing positive end-expiratory pressure, maintaining the patient's compensatory mechanisms by minimizing sedation and muscle relaxation, positioning the patient to minimize compressive effects of the mass on the vital thorax structures, and early consultation with pediatric specialists to develop a shared-emergency treatment strategy and to secure an expedited disposition to the appropriate venue of care.