Granulomatous Thyroiditis

Definition

Clinical Features

• Typical presentation:
  • middle-aged woman
  • sore throat
  • painful deglutition
  • marked tenderness on palpation in thyroid region
  • often associated fever and malaise1
• Once initial process subsides:
  • usually there is complete resolution
  • may develop:
    • pressure symptoms
    • mild hypothyroidism

Pathogenesis

• Etiology not known
• Often follows infection of upper aerodigestive tract
• Nonbacterial nature
• Viral etiology often suggested, but not conclusively proved2

Gross Pathology

• Usually involves entire gland
• Enlargement:
  • often asymmetric:
  • typically to approximately twice normal size
• Advanced stage:
  • involved areas are firm
  • usually little or no adherence to surrounding structures (in contrast to Riedel's thyroiditis)

Histopathology

• Areas of:
  • marked inflammation
  • granulomas containing foreign body giant cells
• Characteristically:
  • the granulomas surround follicles and are not very distinct
  • the multinucleated giant cells (most are histiocytic) engulf colloid (Fig. 1
    

    Fig. 1: Granulomatous thyroiditis showing multiple granulomas centered in thyroid follicles.

    )
  • caseation necrosis is consistently absent
  • areas of fibrosis in a patchy distribution
  • Different stages of the same process may be seen in the same gland3

Special Stains and Immunohistochemistry

• Late stage:
  • strong immunoreactivity for CA19-9
• Acute stage:
  • positivity for CEA in the center of the granuloma4

Other Investigations

• Initial phase, typically:
  • elevated serum T4 and T3
  • complete suppression of 131I uptake

Differential Diagnosis

Genetics

• Associated with HLA-B35 haplotype5