Thyroid & parathyroid


Bethesda system


Editor-in-Chief: Debra L. Zynger, M.D.
Ayana Suzuki, C.T.
Andrey Bychkov, M.D., Ph.D.

Last author update: 21 April 2022
Last staff update: 6 July 2023 (update in progress)

Copyright: 2014-2023,, Inc.

PubMed Search: Bethesda thyroid adequacy

See Also: Nondiagnostic / unsatisfactory

Ayana Suzuki, C.T.
Andrey Bychkov, M.D., Ph.D.
Page views in 2022: 2,066
Page views in 2023 to date: 2,344
Cite this page: Suzuki A, Bychkov A. Adequacy. website. Accessed November 29th, 2023.
Definition / general
  • Assessment of adequacy is the first step in the evaluation of a thyroid fine needle aspiration (FNA) sample (Clark: Thyroid Cytopathology, 1st Edition, 2005)
    • Rapid, low magnification review of all cytologic slides by pathologist or cytotechnologist
    • Rapid on site evaluation helps assess adequacy after sampling; if smear is inadequate, the thyroid nodule can be reaspirated immediately
  • Factors influencing adequacy (Ali: The Bethesda System for Reporting Thyroid Cytopathology, 2nd Edition, 2018):
    • Nature of the nodule (location, size, cystic component)
    • Skills of operator and reader
    • Technical setup (gauge size, ultrasound guidance, etc.)
    • Criteria of adequacy
Essential features
  • Adequate specimen should contain ≥ 6 groups of well visualized follicular cells (≥ 10 per cluster)
  • A minimum number of follicular cells is not required for samples with cytologic atypia or if inflammation or abundant colloid are present
  • FNA smear should contain ≥ 6 groups of well visualized follicular cells (≥ 10 cells/group), preferably on a single slide
  • Exceptions (a minimum number of follicular cells is not required)
    • Solid nodules with cytologic atypia, which qualify into categories III - VI
    • Solid nodules with inflammation are considered benign (Diagn Cytopathol 2008;36:407, Diagn Cytopathol 2008;36:161)
      • Only numerous inflammatory cells
      • Lymphocytic thyroiditis, thyroid abscess or granulomatous thyroiditis
      • Nodules with abundant colloid are placed in the benign category even in the absence of follicular epithelium (Endocr Res 2015;40:215)
  • Same criteria of adequacy are applicable to thyroid liquid based preparations; however, some differences between conventional smears and liquid based preparations should be considered (Kakudo: Thyroid FNA Cytology, 2nd Edition, 2019):
    • Liquid based preparation contains increased amount of follicular cells, especially cell clusters and atypical cells
    • Decreased background components (fresh blood, watery colloid and inflammatory cells)
Cytology description
  • Adequate quantity / cellularity as per criteria above
  • Satisfactory quality (fixation and staining)
Cytology images

Contributed by Ayana Suzuki, C.T.

Adequate with macrofollicles

Adequate with thick colloid only

Adequate with atypical cells

Adequate with thyroiditis

Inadequate / blood obscured

Nondiagnostic dried or acellular

Images hosted on other servers:

Inadequate / blood obscured

Nondiagnostic dried or acellular


Thyroid fine needle aspiration and smearing techniques

Essential thyroid cytopathology

Board review style question #1
Which cytologic appearance of thyroid FNA specimen is classified as adequate?

  1. 3 groups with 10 follicular cells
  2. Abundant thick colloid only
  3. Air dried specimen without any atypical cells
  4. Foamy histiocytes only
  5. Respiratory epithelium only
Board review style answer #1
B. Abundant thick colloid

When the aspirated material contains only abundant thick colloid and no follicular epithelium, it is qualified as adequate. Colloid may have variable appearance. It is important to recognize a substance as a colloid, not blood. 3 groups with 10 benign follicular cells are not sufficient to be qualified as diagnostic per the current criteria.

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Reference: Adequacy
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