Thyroid cytology

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Author: Mikael Häggström [note 1]


A minimum number of 6 clusters with 10 cells each has been arbitrary established to assume adequacy for a definitive diagnosis.[1] The presence of characteristic cells may still confer a definitive diagnosis, but otherwise, the report will simply state inadequate number of cells.

Risk stratification

Papillary thyroid carcinoma, with typical features shown. Pap stain.

Look at least for the following imaged features, and classify findings as per the Bethesda system:

Bethesda system
Category Description[2] Example report
I Non diagnostic/unsatisfactory
II Benign (colloid and follicular cells) Thyroid aspiration, right upper pole:
Negative for malignant cells.
Clusters of benign follicular epithelial cells and colloid. Findings are consistent with a benign hyperplastic nodule. (Bethesda category II)
III Atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS) (follicular or lymphoid cells with atypical features) Thyroid aspiration, right mid pole:
Clusters of atypical follicular cells of undetermined significance (Bethesda category III).
IV Follicular nodule/suspicious follicular nodule (cell crowding, micro follicles, dispersed isolated cells, scant colloid)
V Suspicious for malignancy
VI Malignant


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.

Main page


  1. Michael, Claire W.; Pang, Yijun; Pu, Robert T.; Hasteh, Farnaz; Griffith, Kent A. (2007). "Cellular adequacy for thyroid aspirates prepared by ThinPrep: How many cells are needed? ". Diagnostic Cytopathology 35 (12): 792–797. doi:10.1002/dc.20768. ISSN 87551039. 
  2. "The bethesda system for reporting thyroid cytopathology: interpretation and guidelines in surgical treatment ". Indian Journal of Otolaryngology and Head and Neck Surgery 64 (4): 305–311. December 2012. doi:10.1007/s12070-011-0289-4. PMID 24294568. 
  3. Diagram by Mikael Häggström, MD. Source data: Arul P, Masilamani S (2015). "A correlative study of solitary thyroid nodules using the bethesda system for reporting thyroid cytopathology. ". J Cancer Res Ther 11 (3): 617-22. doi:10.4103/0973-1482.157302. PMID 26458591. Archived from the original. . 
  4. Ayana Suzuki, C.T., Andrey Bychkov, M.D., Ph.D.. Thyroid & parathyroid - Follicular neoplasm. Last author update: 21 April 2022. Last staff update: 12 May 2022
  5. Costigan DC, Shaar M, Frates MC, Alexander EK, Barletta JA, Cibas ES (2020). "Defining thyroid spherules: A benign cytomorphologic feature that mimics microfollicles. ". Cancer Cytopathol 128 (3): 171-176. doi:10.1002/cncy.22219. PMID 31856389. Archived from the original. . 
  6. Image by Mikael Häggström, MD. References for findings:
    - Ayana Suzuki, C.T., Andrey Bychkov, M.D., Ph.D.. Hürthle cell neoplasm. Pathology Outlines. Last author update: 7 May 2020. Last staff update: 12 May 2022
    - Shawky M, Sakr M (2016). "Hurthle Cell Lesion: Controversies, Challenges, and Debates. ". Indian J Surg 78 (1): 41-8. doi:10.1007/s12262-015-1381-x. PMID 27186039. PMC: 4848220. Archived from the original. . 

Image sources

  1. . 4. 2021. Archived from Sharma Avishesh Singh , Ajay Sahu the original. . 
    - "This is an Open Access article that uses a funding model which does not charge readers or their institutions for access and distributed under the terms of the Creative Commons Attribution License ("