Thyroid gland

Topic Completed: 1 March 2009

Minor changes: 22 August 2019

Copyright: 2003-2018,, Inc.

PubMed search: histology [title] thyroid

Shahid Islam, M.D., Ph.D.
Page views in 2019: 12,337
Page views in 2020 to date: 4,061
Cite this page: Islam S. Histology. website. Accessed May 29th, 2020.
Definition / general
  • Divided into lobules of 20 - 40 round to oval follicles, each 50 - 500 microns, with a single layer of cuboidal to low columnar epithelium
  • Lumen contains colloid, which is scalloped and pale in follicles with active secretory activity, densely eosinophilic in inactive follicles and more flocculent ("like a clump or tuft of wool") and basophilic in elderly
  • Stroma contains C cells, formerly called parafollicular cells (actually are intrafollicular), derived from neural crest
  • C cells represent 0.1% of gland, produce calcitonin, are present in middle and upper third of lateral lobes along central axes, are not present in extreme upper and lower poles or in isthmus
  • Usually 10 C cells per low power field in adults
  • C cells are more numerous in neonates, decrease in adults, increase and appear as nodular aggregates after age 60 years
  • C cells have pale / clear cytoplasm, oval nuclei, difficult to identify with H&E, use calcitonin stain
  • Sanderson's polsters: collections of small follicles projecting into lumen of large actively secreting follicles; may resemble papillary carcinoma
  • Oncocytes (Hürthle cells, oxyphilic cells, Ashkenazy cells): large cells with abundant deeply eosinophilic granular cytoplasm and numerous mitochondria
Microscopic (histologic) images
Scroll to see all images.

Contributed by Andrey Bychkov, M.D., Ph.D.

Perinuclear brown pigment


Sanderson's polster

Thyroid follicular epithelium

Follicular colloid

Normofollicular thyroid

Macrofollicular thyroid

Microfollicular thyroid

Pyramidal lobe

Pericapsular fat

Adipose metaplasia

Perithyroid thyroid follicles

Intrathyroidal muscle

Calcium oxalate crystals in the colloid

PAS staining

Mucicarmine staining

Thyroglobulin expression

TTF1 expression

PAX8 expression

TTF2 nuclear expression

NIS membranous expression

Cluster of C cells

Location of C cells in relation to follicle

Pericapillary location of C cells

Clustered distribution of C cells

Calcitonin immunohistochemistry

Proliferation in adult thyroid

Prominent vascular network

Capillary network

Solid cell nests

Histologic mimics of SCN

Solid cell nests: p63

Solid cell nests: thyroglobulin-

Images from AFIP:

C cells (calcitonin
stain); cells are
polyhedral and

Follicles lined by flattened epithelium

Normal adult follicles are round to oval

Follicles lined by cuboidal epithelium

Colloid is flocculent - most likely artifactual, not significant

Tangential section
of normal thyroid
follicle may resemble
C cell hyperplasia

Images hosted on other servers:

Follicles lined by flattened epithelium and filled with colloid

Rich vascular supply

Thyroid and parathyroid glands

Papillary structures

C cells (calcitonin stain)

Images hosted on PathOut server:

Images from AFIP:

Ectopic cartilage

Skeletal muscle

Squamous metaplasia

Positive stains
Electron microscopy description
  • Follicular cells: abundant granular endoplasmic reticulum, well developed Golgi, prominent lysosomes, luminal (apical) microvilli, well developed desmosomes with terminal bars between cells, small mitochondria, may contain lipofuscin; nuclei are round with homogeneous chromatin
  • C cells: intrafollicular (separated from thyroid interstitium by follicular basal lamina), numerous dense core neurosecretory granules (type I are 280 nm, moderately electron dense and present in most C cells; type II are 130 nm, more electron dense and rare)
Electron microscopy images
Images hosted on PathOut server:

Images from AFIP:

Follicles have luminal microvilli

Intrafollicular C cell

Images hosted on other servers:

Follicular cells


By John R. Minarcik, M.D.

Clinical features
  • Adipose metaplasia (mature adipose tissue between follicles or near capsule)
  • Intrathyroidal cartilage, skeletal muscle or salivary gland
  • Melanosis of follicular cells in old age (pigment granules also contain colloid, Ultrastruct Pathol 1998;22:401); see also Black thyroid
  • Calcification is associated with vessels in elderly, has no laminations (in contrast to psammoma bodies)
  • Squamous metaplasia is rare in normal thyroid, more common in thyroid disorders
Case reports
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