Figure 16a. Figures 15, 16. (15) Cystic hygroma in a 28-year-old man with a 4-week history of painless swelling of the left side of the neck unresponsive to antibiotics. Fine-needle aspiration yielded serous fluid. Contrast-enhanced CT scan shows a hypoattenuated mass (h) within the posterior cervical space deep to the sternocleidomastoid muscle. At surgery, the mass was adherent to the internal jugular vein. (Courtesy of the Department of Radiology, Naval Medical Center, San Diego, Calif.) (16) Cystic hygroma in a newborn boy. (a) Photograph shows a large bilobulated mass extending from the neck into the chest wall, axilla, and lower face. (b) Sagittal CT scan shows erosion of the mandible and invasion of the oral cavity. Multiple septa are seen.