Thyroid & parathyroid


Riedel thyroiditis

Last author update: 1 March 2009
Last staff update: 17 August 2023 (update in progress)

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PubMed Search: Riedel's thyroiditis

Shahid Islam, M.D., Ph.D.
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Cite this page: Islam S. Riedel thyroiditis. website. Accessed September 21st, 2023.
Definition / general
  • Densely fibrotic inflammatory process involving thyroid gland and adjacent neck tissue
  • Described in 1896 by German surgeon Bernhard Moritz Carl Ludwig Riedel (Wikipedia)
  • Rare (0.05% of thyroidectomy specimens)
  • Also called Riedel struma, fibrous thyroiditis
  • Slight female predominance, usually age 40 - 60 years
Clinical features
  • Associated with inflammatory fibrosclerosis / multifocal systemic fibrosclerosis (mediastinal or retroperitoneal fibrosis, sclerosing cholangitis, inflammatory pseudotumor of orbit)
  • 65% have antithyroid antibodies
  • Clinically resembles carcinoma
  • In one study, 67% had antithyroid antibodies, supporting an autoimmune mechanism of injury (Am J Clin Pathol 1988;90:715)
Case reports
Gross description
  • Extensive stony hard fibrosis involving a goitrous thyroid gland and infiltration into adjacent muscle and other structures, obliterating tissue planes at surgery
  • Binds soft tissues of neck in an "iron collar," may compress trachea
  • Tan / gray, woody and avascular, no lobules apparent
Microscopic (histologic) description
  • No normal lobular pattern
  • Follicles are obliterated or compressed by extensive dense fibrous tissue, which also infiltrates adjacent skeletal muscle
  • Patchy lymphocytes (B & T cells), plasma cells (IgA, lambda) and eosinophils, inflammation in walls of trapped veins
  • 25% have adenoma centrally in fibrous mass
  • No oncocytic cells, no giant cells
Microscopic (histologic) images

AFIP images

Atrophic thyroid follicles

Resembles papillary microcarcinoma

Follicles within scar irregular

Heavy inflammatory infiltrate, venous wall

Images hosted on other servers:

Massive scarring and lymphohistiocytic infiltrate

Obliterating phlebitis

Virtual slides

Images hosted on other servers:

Invasive fibrous thyroiditis

Cytology description
Differential diagnosis
Additional references
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