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Thyroid gland

Bethesda guidelines for Cytology


Reviewer: Michael Constantinescu, M.D. (see Reviewers page)
Revised: 21 March 2011, last major update March 2011
Copyright: (c) 2010-2011, PathologyOutlines.com, Inc.


● Most (65%) thyroid nodules are benign
● Includes adenomatoid or hyperplastic nodules, colloid nodules, nodules in Grave’s disease, or thyroiditis (Hashimoto’s, granulomatous, acute, etc.)
● Risk of malignancy is approximately 0-3%; false negative rate is 1-10%
● Follow up recommended at 6 to 18 month intervals for at least 3 to 5 years after initial diagnosis by physical exam and ultrasound
● Repeat FNA if nodules show rapid growth or ultrasound abnormalities (e.g. microcalcifications, hypoechogenicity, irregular margins)

Sample reports

1. Benign
      - Benign follicular nodule
2. Benign
      - Benign thyroid nodule, consistent with colloid nodule
3. Benign
      - Consistent with lymphocytic (Hashimoto’s) thyroiditis
Comment: The findings are consistent with lymphocytic (Hashimoto’s) thyroiditis in the proper clinical setting

Benign follicular nodule

● Adequate, sparse to moderate cellularity
● Thin colloid (watery, chicken-wire, mosaic coating film) or thick colloid (cracks, dense)
● Follicle cells: monolayer or honeycomb sheets, occasional 3-dimensional balls, but mostly with evenly spaced nuclei
● Cells have scant and delicate cytoplasm, round to oval nuclei with uniform chromatin, 7-10 microns in diameter; some anisocytosis, no significant atypia
● Rare microfollicles, some Hurthle cells may be present

Other benign entities

● Graves disease: additional features include Hurthle cells and lymphocytes in background, follicle cells with foamy cytoplasm, prominent nucleoli, flame cells (cytoplasmic vacuoles with frayed pink edges on DiffQuick), some microfollicles
● Hashimoto (lymphocytic) thyroiditis: additional features include possible increased cellularity (although minimal criteria for follicle cells adequacy are not required), polymorphic lymphocytic population including possible intact lymphoid follicles, sheets or single Hurthle cells (some pleomorphic, atypical Hurthle cells may be seen)
● Acute thyroiditis: additional findings include acute inflammatory cells, necrosis, macrophages, blood
● Riedel’s thyroiditis: acellular/hypocellular, collagen strands, benign spindle cells

End of Thyroid gland > Bethesda guidelines for Cytology > Benign

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