Superior Herniation of Thymus

Yes, the amount of grey in my beard increases exponentially on a daily basis now. Yes, there are days that I may seem “set in my ways.” Sure, my sister just turned 50! (happy birthday Big Sis!!) Yet, despite my rapid physical deterioration, our job prevents my mind from becoming quiescent (at least for now). In fact, just this past week, my good friend, Dr. Clothier, taught me something I had never known (or seen) before! Let us take a second to review this unusual, and potentially alarming, feature – Superior Herniation of Thymus:

Superior Herniation of the Thymus

  • Occurs when a NORMAL thymus intermittently herniates out of the thorax. [Stuut, 2016; Ranga, 2015; Senel, 2011; Senel, 2008]
    • Migrates cephalad.
    • Presents as suprasternal mass.
  • Episodes noted when intrathoracic pressure is increased. [Stuut, 2016; Senel, 2011]
    • Crying
    • Yelling
    • Coughing or Sneezing
    • Valsalva
  • The swelling should: [Ranga, 2015]
    • Be soft
    • Have poorly defined margins
    • Not be tender
  • Anatomy: [Stuut, 2016; Ranga, 2015; Senel, 2008]
    • During development, the thymus migrates caudally into the anterior mediastinum.
      • Failure to descend can lead to ectopic cervical thymus.
      • Incomplete descent can lead to cervical extension of the thymus.
    • The thymus is relatively large at first.
      • At birth, the thymus extends from the manubrium to the 4th costal cartilage.
      • It is its relative largest size (compared to body) at 3 years of age.
    • Thymus continues to grow until puberty and then involutes.
  • Evaluation: [Stuut, 2016; Ranga, 2015]
    • Ultrasound
      • Initial imaging modality of choice
      • Should show normal thymus tissue that is contiguous with normal mediastinal thymus.
      • May show dynamic changes of position with increased intrathoracic pressure.
    • MRI
      • Can confirm the masses extension to the mediastinal thymus. [Ranga, 2015]
      • Superior anatomic definition to that of CT. [Senel, 2008]
  • Management: [Stuut, 2016]
    • Since the thymus will involute, no surgical intervention is required.
    • Biopsy is also unnecessary.
    • Educate (ourselves and our patients!)

Anterior Neck Mass: Considerations

  • Ddx (abridged):
  • Ddx of Neck Mass that Increases with Valsalva: [Stuut, 2016; Ranga, 2015; Senel, 2008]
    • Herniation of Mediastinal Thymus
    • Apical Lung Herniation
    • Jugular Vein Phlebectasy / Aneursyms
      • Fusiform dilation of the jugular vein.
      • Defined on ultrasound doppler.
    • Laryngocele
      • Rare in children (more commonly seen in adult males)
      • Usually extends to paraglottic area and lateral aspects of the neck.
      • May contain air, fluid, pus, or combination of them all.
      • Ultrasound may help distinguish it from others, but CT is preferred.

Moral of the Morsel

  • Not all masses are bad. Some are just normal tissues mal-positioned.
  • Know your neck masses. They will catch people’s attention, so know how to evaluate them.
  • Accentuation with Valslava? May be a simple problem that will resolve on its own. Consider Superior Herniation of the Thymus… and get an Ultrasound.


Stuut M1, van Zwieten G2, Straetmans JM3, Lacko M2, Stumpel CT4. The inflatable thymus herniation of the normal mediastinal thymus: A case report and review of the literature. Int J Pediatr Otorhinolaryngol. 2016 Apr;83:74-7. PMID: 26968057. [PubMed] [Read by QxMD]
Ranga U1, Aiyappan SK, Sujatha B, Pathy A, Veeraiyan S. Unusual Cause of Suprasternal Swelling: Cervical Extension with Herniation of Mediastinal Thymus. Indian J Pediatr. 2015 Jul;82(7):657-8. PMID: 25676318. [PubMed] [Read by QxMD]
Su SC1, Hess T, Whybourne A, Chang AB. Intermittent midline suprasternal neck mass caused by superior herniation of the thymus. J Paediatr Child Health. 2015 Mar;51(3):344-6. PMID: 25266888. [PubMed] [Read by QxMD]
Senel S1, Erkek N, Otgun I, Cinar G, Cifci A, Yoney A. Superior herniation of the thymus into the neck–a familial pattern. J Thorac Imaging. 2008 May;23(2):131-4. PMID: 18520572. [PubMed] [Read by QxMD]


Sean M. Fox
Sean M. Fox
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