title: Ectopic Intrathyroidal Thymus in Childhood: A Sonographic Finding Leading to Misdiagnosis.
abstract: BACKGROUND
  During gestation, the primordial thymus migrates from the pharynx to the anterior mediastinum, thus thymic tissue can remain at any point along this path. Intrathyroidal thymic remnants are rare, and their sonographic patterns have only recently been described. This retrospective study presents the sonographic appearance of ectopic intrathyroidal thymus and emphasizes the role of sonography in order to avoid misdiagnosis.
  
  
  METHODS
  The population consisted of 42 children, 3.5-14 years old, who had a thyroid sonogram performed due to a positive family history or symptoms indicative of thyroid disease, and ectopic intrathyroidal thymus was recognized.
  
  
  RESULTS
  In all patients, the same pattern was revealed: a fusiform intrathyroidal lesion, with no mass effect, homogeneously hypoechoic, with diffuse bright internal echoes. The similarity to the characteristic sonographic pattern of the normal mediastinal thymus was crucial for the diagnosis of ectopic intrathyroidal thymic tissue. In 8 cases, a normal elongated thymus was found connected to the thyroid with an accessory lobe embedded in the lower thyroid pole. The above sonographic appearances mimicked a thyroid nodule.
  
  
  CONCLUSIONS
  Awareness of the sonographic patterns of the ectopic intrathyroidal thymus is mandatory to avoid misdiagnosis. In most cases, further investigation is unnecessary, but sonographic follow-up should be recommended.
authors.affiliation: Division of Endocrinology, Growth and Development, 'P. &amp; Α. Kyriakou' Children's Hospital, Athens, Greece.
authors.forename: Elpis-Athina
authors.initials: EA
authors.lastname: Vlachopapadopoulou
authors.forename: Marina
authors.initials: M
authors.lastname: Vakaki
authors.forename: Fotini-Eleni
authors.initials: FE
authors.lastname: Karachaliou
authors.forename: Irene
authors.initials: I
authors.lastname: Kaloumenou
authors.forename: Kleanthi
authors.initials: K
authors.lastname: Kalogerakou
authors.forename: Christina
authors.initials: C
authors.lastname: Gali
authors.forename: Stefanos
authors.initials: S
authors.lastname: Michalacos
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D013950:Thymus Gland / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D013961:Thyroid Gland / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D014463:Ultrasonography