Sonographic findings in ectopic cervical thymus in an infant

We present the case of a 28‐day‐old boy with ectopic thymic tissue in the neck. Sonography showed a well‐delineated, homogeneous lesion in the left submandibular region that was isoechoic relative to the mediastinal thymus. The lesion had angular margins and lacked a mass effect despite its large size (3 × 2 cm). On power Doppler imaging, arteries with an intermediate‐impedance flow pattern were seen entering the lesion from the inferior and lateral margins. On both T1‐ and T2‐weighted MR images, the lesion was isointense relative to the mediastinal thymus and had higher and lower signal intensity than muscle and fat, respectively. A sonographically guided needle biopsy confirmed the diagnosis of ectopic thymus. © 2001 John Wiley & Sons, Inc. J Clin Ultrasound 29:523–526, 2001.