Editor's note: Each month, this department features a discussion of an unusual diagnosis. A description and images are presented, followed by the diagnosis and an explanation of how the diagnosis was determined. As always, your comments are welcome via email at pedann@Healio.com. For diagnosis, see page 58Case Challenge A 6-year-old female was brought to the emergency department 6 hours after sustaining blunt trauma to the neck. She was playing outside her house when a small motorized bicycle fell on her neck. She was in mild discomfort immediately after the injury and developed significant swelling with tenderness over the following hours. She complained of pain upon swallowing and pain with movement of the neck. She had no significant medical history or prior trauma. Her vaccinations were current and no ill contacts were identified. Her growth and developmental milestones were all attained in normal stages.On physical exam, she was afebrile. No evidence of erythema or ecchymosis was seen. She exhibited left-sided cervical swelling that was warm to the touch and tender below the left submandibular angle (Figure 1). She demonstrated limited cervical range of motion. Kernig's and Brudzinski's signs were negative. Inspection of her oropharynx showed no lesions, erythema, exudates, or edema. On palpation, a 3.5-cm × 2-cm mass was found in the left submandibular region and a 1.5-cm × 1-cm posterior cervical lymph node was palpated.Her initial labs showed marked leukocytosis. Sonographic studies revealed an isoechoic mass in the left upper neck. Computed tomography angiography of the neck with contrast demonstrated no vascular injury. A computed tomography (CT) scan of the neck confirmed the absence of any bony fractures and revealed the diagnosis (Figures 2 and 3).