Figure 17a. Figures 17–19. (17) Cystic hygroma in a 20-month-old girl with swelling under the right jaw and neck noted by the mother. (a) Contrast-enhanced CT scan shows a large right-sided neck mass with fluid-fluid levels (arrows) indicative of recent hemorrhage. (b) Axial T1-weighted image shows heterogeneous signal intensity within the mass (m), which fills the right parotid space and portions of the mandibular space. Areas of hyperintensity correspond to regions of hemorrhage. (c) Coronal T1-weighted image shows extension of the mass into submandibular and sublingual spaces. (d) Photograph of the specimen shows the cystic lobules (arrows) of the multiloculated mass; cut surface (arrowheads) of a lobule reveals hemorrhage. (18) Cystic hygroma. Axial T1-weighted image shows a well-defined mass (m) within the right posterior cervical space that displaces the adjacent sternocleidomastoid muscle. (19) Cystic hygroma in a 36-year-old woman with a left-sided neck mass that enlarged during viral upper respiratory infections. Coronal T1-weighted image shows a large hypointense mass in the left side of the neck extending from the submandibular space to the thoracic inlet. Multiple septa (arrows) cross the lesion.