Thyroid gland
Bethesda guidelines for cytology

Author: Phillip A. Williams, M.D., M.Sc., Shahidul Islam, M.D., Ph.D. (see Authors page)

Revised: 27 July 2018, last major update April 2014

Copyright: (c) 2014-2018,, Inc.

PubMed Search: Bethesda guidelines thyroid benign
Cite this page: Williams, P.A., Islam, S. Benign. website. Accessed August 16th, 2018.
Definition / general
  • Based upon the 2009 Bethesda system for thyroid cytopathology (Am J Clin Pathol 2009;132:658)
  • 60 - 70% of thyroid FNAs
  • Primary benefit of thyroid FNA is ability to reliably make a benign diagnosis
  • Most common are adenomatoid or hyperplastic nodules; also colloid nodules, thyroiditis (Hashimoto, granulomatous, acute, etc.)
  • Also subacute / de Quervain thyroiditis, amyloid goiter (usually secondary to systemic condition), black thyroid (due to chronic tetracycline use), reactive changes, radiation changes (external beam and radioactive iodine)
  • Adenomatoid nodules (benign multinodular goiter) are 15 - 20× more common in women
  • Chronic lymphocytic (Hashimoto) thyroiditis: 95% female, peaks at ages 40 - 60 years
Radiology description
  • Adenomatoid nodules: multinodular goiter on ultrasound
  • Chronic lymphocytic (Hashimoto) thyroiditis: heterogeneous appearance on ultrasound
Radiology images

Images hosted on PathOut server:

Contributed by Ayana Suzuki, Cytotechnologist, Japan:

Isoechoic nodule

Hypoechoic nodule

Large cyst

Large multilocular cyst

  • Due to false negative rate of 0 - 3%, recommended to follow up with repeat assessment by palpation or ultrasound at 6 - 18 month intervals for 3 - 5 years (Thyroid 2009;19:1167)
  • Follow up with repeat FNA if significant interval growth or suspicious findings (microcalcifications, hypoechogenicity, irregular margins) on ultrasound
  • Surgery for benign thyroid disease is not recommended unless compressive symptoms or younger age group (Endocr Rev 2003;24:102)
Clinical images

Images hosted on PathOut server:

Contributed by Ayana Suzuki, Cytotechnologist, Japan:

Flocculated appearance

Clear fluid

Microscopic (histologic) description
  • Benign follicular nodule (most common pattern):
    • Adequate, low to moderate cellularity
    • Predominately macrofollicles with fragmented monolayer or honeycomb sheets, occasional intact spheres with evenly spaced cohesive uniform cells
    • Abundant colloid:
      • Thin colloid is watery, chicken wire, mosaic coating film
      • Thick colloid has hyaline texture, hard edges, cracking artifact
      • Liquid based colloid has a folded tissue paper appearance
    • Cells have scant to moderate cytoplasm, round nuclei with uniform coarse chromatin, no significant atypia
    • Minor components: Hürthle cells, microfollicles

  • Chronic lymphocytic (Hashimoto) thyroiditis:
    • Very cellular consisting mostly of lymphocytes, tingible body macrophages and dendritic-lymphocytic aggregates
    • Occasional follicular cells and clusters of Hürthle cells (focal clearing and nuclear grooves)
    • Scant or absent colloid

  • Subacute (de Quervain) thyroiditis:
    • Usually diagnosed clinically, FNA is rare
    • Variable cellularity, prominent multinucleated giant cells, granulomas (diagnostic but rare), lymphocytes (Diagn Cytopathol 2006;34:18)

  • Riedel thyroiditis:
    • Usually dry tap (due to dense fibrosis)
    • Fibrous tissue, myofibroblasts, mixed inflammatory cell infiltrate

  • Amyloid goiter:
    • Amyloid appears similar to colloid
    • Diagnosis is based on amyloid's apple green birefringence with polarized light and a Congo red stain

  • Black thyroid:
    • Follicular cells with abundant dark brown (darker than hemosiderin) pigment
    • Pigment stains positive with Fontana-Masson stain

  • Radiation changes:
    • Follicular cells in sheets with large variation in cell size, abundant cytoplasm (occasionally vacuolated), marked nuclear atypia
    • Similar to radiation changes seen elsewhere

Cytology images

Images hosted on PathOut server:

Contributed by Ayana Suzuki, Cytotechnologist, Japan:

Watery colloid

Cracking colloid

Follicular clusters

3D structures

Paravacuolar granules

Lymphocytes and oncocytes

Giant cell

Histiocytes and squame

Images hosted on other servers:

Subacute (de Quervain) thyroiditis:

Various images

Amyloid goiter:

Embedded fibroblasts

Differential diagnosis