Definition of Goiter

• Both greatest diameter and goiter weight have been used to define thyroid enlargement:
  • In studies, methods for determining goiter size range from:
    • Physical examination measured in centimeters, to physical examination estimated in grams, to surgical specimen measured in centimeters or grams
    • Preoperative imaging diameters may also be used
• The definition of goiter varies substantially among reports:
  • McHenry 80 g as the threshold value
  • Russell 100 g as the threshold value
  • Clark 200 g as the threshold value
• Studies investigating radioiodine treatment for multinodular goiter:
  • Often define significant goiter as:
    • Greater than 100 g
• Hegedus, Nygaard, and Hansen found that goiter surgical specimens:
  • Averaged:
    • 30 g for unilateral resection
    • 64 g for bilateral resection
• Katlic, Grillo, and Wang reported that:
  • The average weight of substernal goiter was:
    • 104 g (range 25 to 357 g)
    • Greatest diameter averaging 9 cm (range 5 to 19 cm)
• In a series of more than 200 cervical and substernal goiters treated at Massachusetts Eye and Ear Infirmary and Massachusetts General Hospital:
  • The mean weight was 143 g
  • The mean goiter size was 10.5 cm
• The World Health Organization (WHO) 1960 grading system for clinical assessment of goiter defines:
  • Stage 0 as no enlargement
  • Stages 1 to 3 describe progressive goiter enlargement:
    • Stage 1A:
      • Includes patients with palpable abnormalities
    • Stage 1B:
      • Includes patients with palpable and visual abnormalities with the neck in extension
    • Stage 2:
      • Is defined as a goiter that is visible with the neck in neutral position
    • Stage 3:
      • As a goiter that is able to be visualized at a considerable distance
• The WHO 1994 goiter classification system is more streamlined:
  • Grade 0:
    • Is defined as no palpable or visual abnormality
  • Grade 1:
    • Is defined as a palpable thyroid mass that is not visualized with the neck in neutral position
  • Grade 2:
    • As a visually apparent mass with the neck in neutral position

• Substernal GoiterSynonyms:
  • Substernal goiter and its subtypes have been termed:
    • Retrosternal, subclavicular, intrathoracic, mediastinal, aberrant, wandering, and spring goiter, as well as goiter mobile and goiter plongeant
• Numerous definitions and classification schemes have been proposed for substernal goiter:
  • Lahey and Swinton defined substernal goiter as:
    • A “gland in which the greatest diameter of the intrathoracic component by x-ray was well below the upper aperture of the thoracic inlet”
  • Crile, in 1939, simply defined substernal goiter as:
    • A lesion extending to the aortic arch
  • Lindskog and Goldenberg in 1957 defined substernal goiter as:
    • A goiter whose lower border radiographically reaches the transverse process of the fourth thoracic vertebra or lower
  • Katlic, Grillo, and Wang described substernal goiter as:
    • When greater than 50% of the goiter is present substernally
  • Sanders et al. defined substernal goiter as:
    • That which requires mediastinal exploration and dissection for removal
• Substernal classification schemes:
  • Higgins based his classification scheme on the percentage of goiter in the neck versus the percentage of goiter in the chest with:
    • Greater than 50% in the neck being described as:
      • Substernal
    • Greater than 50% in the chest as:
      • Partially intrathoracic
    • Greater than 80% in the chest as:
      • Completely intrathoracic
  • Cho, Cohen, and Som offered a grading system relating grade to percentage of goiter within the chest:
    • Grade I is defined as 0% to 25% of the goiter within the chest
    • Grade II as 26% to 50% of the goiter within the chest
    • Grade III as 51% to 75% of the goiter within the chest,
    • Grade IV as greater than 75% of the goiter within the chest
  • Shahian offered an interesting and detailed classification scheme:
    • Type I substernal goiter is associated with the anterior mediastinal extension:
      • Type IA involves “isolated” anterior mediastinal disease
      • Type IB involves “extensive” substernal involvement
    • Type II involves posterior mediastinal involvement:
      • Type IIA being isolated posterior mediastinal goiter
      • Type IIB posterior mediastinal goiter with ipsilateral extension relative to the thyroid lobe of origin
      • Type IIC contralateral extension relative to the thyroid lobe of origin:
        • C1 being retrotracheal
        • C2 being retroesophageal course
• A classification system for substernal goiters is most useful when it takes into account the features of substernal goiters that must be appreciated to extract them safely:
  • Substernal goiter simply as those goiters that are associated with substernal extension such that the thoracic component requires mediastinal dissection to facilitate extraction
  • All substernal goiters require axial computed tomographic (CT) scanning to differentiate between the various subtypes
  • Such differentiation provides tremendously useful surgical information

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