Reviewer: Shahidul Islam, M.D., Ph.D. (see Reviewers page) Revised: 7 June 2013, last major update March 2009 Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.
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
Follicular cells: thyroglobulin (very specific, weaker staining in oncocytic cells), TTF1, low molecular weight keratin; also EMA, vimentin, T3 (triiodothyronine), T4 (thyroxine), ER beta (not alpha), PgR Note: thyroglobulin may leak out of follicular cells and create false positivity in adjacent cells
Colloid: thyroglobulin, Alcian blue, PAS, T3, T4
C cells: calcitonin, calcitonin gene related peptide (CGRP), neuron specific enolase, chromogranin A, synaptophysin, CEA, somatostatin; C cells are metachromatic with toluidine blue; C cells are NEGATIVE for thyroglobulin
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
"Shotgun Histology Thyroid"
by John R. Minarcik, M.D.
End of Thyroid gland > General > Histology
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