Review Question - QID 109390

A 3-year-old male is brought by his mother to the pediatrician because she is concerned about a lump in his neck. She reports that the child was recently ill with a cough, nasal congestion, and rhinorrhea. She also noticed that a small red lump developed on the patient’s neck while he was sick. Although his cough and congestion subsided after a few days, the neck lump has persisted. The child has no notable past medical history. He was born at 39 weeks gestation and is in the 55th percentiles for both height and weight. His temperature is 98.6°F (37°C), blood pressure is 105/65 mmHg, pulse is 90/min, and respirations are 18/min. Physical examination reveals a small, soft, rounded mass at the midline of the neck inferior to the hyoid bone. The mass is warm and tender to palpation. It moves superiorly when the patient drinks water. Histologic examination of this lesion would most likely reveal which of the following?