Hyperthyroidism

Author: Mikael Häggström

Fixation

Generally 10% neutral buffered formalin. Fix all thyroids at least overnight to avoid artifactual nuclear atypia.

See also: General notes on fixation

Gross processing

• Weigh
• Measure each lobe and isthmus in 3 dimensions, respectively.
• Ink outer surface, at least if malignancy is suspected.

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  Hemithyroidecomy (lobe + isthmus) or lobectomy, including completion thyroidectomies: Use separate colors over the cut surface and the outer “capsular” surface.

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  None of the outer “capsular” surface should be inked like the cut surface.

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  Intact total thyroidectomy: Separate colors for each lobe and the isthmus.

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  If no appreciable isthmus, Separate colors for each lobe.

Serially section the specimen at 3-4mm intervals, such as follows:

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  Hemithyroidecomy (lobe + isthmus) or lobectomy: Include isthmic orange margins in your transverse sections.

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  Intact total thyroidectomy: Transverse lobe sections and sagittal isthmus sections

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  Short/inconspicious isthmus: The isthmus can be included in the transverse sections.

See also: General notes on gross processing

Microscopic evaluation

The most common cause of hyperthyroidism is Grave's disease (50-80% worldwide). Its typical features are:

• Hyperplastic thyroid follicles with papillary infoldings.
• Diffuse hyperplasia and hypertrophy of follicular cells with retention of lobular architecture.
• Prominent vascular congestion.
• Tall follicular cells with papillae that usually lack fibrovascular cores.
• Nuclei are round, often basally located, and rarely overlap.
• Typically decreased colloid amount, and when present it typically has peripheral scalloping.
• Variable patchy lymphoid stromal infiltrate.

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  Graves' disease - low magnification: exuberant papillary hyperplasia.

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  Graves' disease - medium magnification: cells with round nuclei and even chromatin pattern lining the papillae.

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  Toxic multinodular goiter, whose typical findings are:
  - Variably dilated follicles with flattened hyperplastic epithelium.
  - Nodules may be present (but lack thick capsule in contrast to adenomas).
  - Potentially focal fresh or old hemorrhages, rupture of follicles with granulomatous inflammation, fibrosis, calcification and even osseous metaplasia.
  - Also potentially papillary projections (Sanderson polsters) that may mimic papillary carcinoma, but they lack malignant nuclear features.

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  Amiodarone associated follicular cell damage - high magnification: large thyroid follicles filled with colloid and numerous histiocytes

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  Amiodarone associated follicular cell damage - low magnification: large thyroid follicles filled with colloid and numerous histiocytes (arrow heads)

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  Papillary hyperplastic nodule - high magnification: oncocytic cells lining the papillary structures (arrow)

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  Papillary hyperplastic nodule - low magnification: cystic nodule with papillary architecture (arrow)

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