title: Ectopic intrathyroidal thymus in children: a long-term follow-up study.
abstract: BACKGROUND
  Ectopic intrathyroidal thymus has recently been reported in children as a cause of surgery and/or invasive diagnostic procedures when mistaken for a thyroid nodule. Thymus has a unique appearance at ultrasound (US).
  
  
  METHODS
  We report a follow-up study (mean 34 months, range 6-84) performed by US on 9 children (5 females) with a mean age of 6.3 ± 3.2 years with intrathyroidal thymic inclusions diagnosed by US as 'incidentalomas'. None has palpable nodules.
  
  
  RESULTS
  Intrathyroidal thymic inclusions appeared on US as a hypoechoic area, with regular linear or punctuate internal hyperechoic echoes. The 2 oldest patients (13 and 17 years) showed a regression in both size and hypoechogenicity of thymic inclusions over time--reflecting the normal thymic involution with advancing age.
  
  
  CONCLUSIONS
  Indeed, the lack of progression seen in our 9 patients over a mean time of 34 months confirmed the substantially benign and self-limited nature of this process. The increasing use of thyroid ultrasonography in children may result in an increased detection of intrathyroidal thymic inclusions--an embryologic anomaly that should be considered in the differential diagnosis of thyroid nodules in children and adolescents.
authors.affiliation: Department of Pediatrics, Sapienza University, Rome, Italy. m.segni@mclink.it
authors.forename: Maria
authors.initials: M
authors.lastname: Segni
authors.forename: Raffaela
authors.initials: R
authors.lastname: di Nardo
authors.forename: Ida
authors.initials: I
authors.lastname: Pucarelli
authors.forename: Marco
authors.initials: M
authors.lastname: Biffoni
mesh_terms: D000375:Aging; D002648:Child; D002675:Child, Preschool; D002828:Choristoma / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D008297:Male; D013950:Thymus Gland / Q000000981:diagnostic imaging*; D013959:Thyroid Diseases / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000254:growth & development; D014463:Ultrasonography