Thyroid gland
Cytology - cytodiagnostic groups

Topic Completed: 1 March 2009

Revised: 2 May 2019

Copyright: 2003-2019,, Inc.

PubMed Search: cytodiagnostic thyroid

Shahid Islam, M.D., Ph.D.
Page views in 2018: 6,414
Page views in 2019 to date: 3,422
Cite this page: Islam S. Cytology - cytodiagnostic groups. website. Accessed July 17th, 2019.
Definition / general
  1. Benign colloid nodule (solitary colloid nodule, prominent nodule in multinodular goiter, macrofollicular adenoma)
    • Abundant thick colloid with cracking or bubble pattern and sheets of benign follicular epithelial cells in honeycomb arrangement
    • May have slightly hyperplastic Hürthle cells
  2. Cellular microfollicular lesion (microfollicular adenoma, hyperplastic microfollicular lesion in Hashimoto's or multinodular goiter, low grade / well differentiated follicular carcinoma)
    • Very challenging, often reported as indeterminate or suspicious for malignancy
    • Abundant follicular cells in clusters, acini and small monolayered sheets
    • Cells have scanty, ill defined cytoplasm and oval nuclei with regular nuclear contours
    • Nucleoli vary from indistinct to prominent, no nuclear features of papillary carcinoma
    • 25% with diagnosis of "suggestive of follicular neoplasm" have malignancy at excision (Thyroid 2009;19:33)
  3. Hürthle cell lesion (adenoma, carcinoma or hyperplastic nodule in Hashimoto's or multinodular goiter)
    • Challenging diagnosis
    • Numerous lymphocytes or thick colloid in needle aspirate
    • Sheets and clusters of polygonal epithelial cells with abundant granular, eosinophilic or basophilic cytoplasm, oval nuclei with regular nuclear contours and conspicuous or inconspicuous nucleoli
    • Syncytial clusters of Hürthle (oncocytic) cells and abundant naked tumor cell nuclei are suggestive of Hürthle cell carcinoma (Diagn Cytopathol 1999;20:261)
  4. Primary malignant tumor (papillary, high grade microfollicular, insular, medullary or anaplastic carcinoma; lymphoma)
  5. Cystic lesion (benign colloid nodule, papillary carcinoma, other thyroid neoplasm)
    • Most are benign, and due to hemorrhagic degeneration of a benign colloid nodule
    • Cytology shows colloid material, benign follicular epithelial cells and hemosiderin laden macrophages
    • Papillary carcinoma may show similar changes with only rare tumor cells in smear, diagnostic papillary tumor cells are often present in cell block
  6. Thyroiditis (acute, Hashimoto's, subacute)
  7. Other (Graves' disease, metastatic carcinoma)
  8. Nondiagnostic (malignant disease present in 14% with repeat FNA, Am J Surg 2008;196:398)

Probably benign:
  • Colloid, histiocytes, normal looking follicular cells
  • Nondiagnostic cases with no Hürthle cell change and no atypia (Am J Clin Pathol 2002;118:518)

Suspicious for malignancy (recommend excision):
  • Uniform microfollicular pattern, mitotic activity, predominant oncocytic cytology, nuclear atypia but no history of radiation

Follicular neoplasm:
  • Monotonous population of follicular cells in cohesive groups with nuclear overlapping and crowding, in background of scant colloid

Follicular neoplasm with features suspicious for papillary carcinoma:
  • Follicular cells in loosely cohesive monolayer sheets and follicular groups, focally with nuclear elongation, chromatin clearing and intranuclear grooves, background is watery and thick colloid
Diagrams / tables

Images hosted on other servers:

Cytodiagnostic groups with common nodular lesions

Case reports
  • 70 year old man with diffuse large B cell lymphoma misdiagnosed as anaplastic carcinoma (Cytojournal 2006;3:23)
Cytology images

Images hosted on other servers:

Watery colloid

Indeterminate FNA

Benign colloid nodule:

Thick, deep blue colloid with cracking

Thick, deep blue colloid with bubble pattern

Sheet of benign follicular epithelial cells

ThinPrep versus Pap stain

Hyperplastic thyroid nodule

Hemorrhagic cyst

Cellular microfollicular lesion:

Cells with round nuclei in acini and monolayered sheet

Cells with round nuclei arranged in acini

Solid cellular nodule, microfollicular lesion (Fig 5)

Suspicious for papillary carcinoma:

Rare intranuclear inclusions and abundant colloid

Cellular with
papillary formation,
nuclear inclusions
and grooves

Follicular neoplasms:

FNA: follicular
neoplasm, excision:
follicular adenoma

FNA: suspicious for
papillary carcinoma,
excision: follicular variant
of papillary carcinoma

Follicular neoplasm has enlarged
follicular cells in loosely cohesive
follicles plus isolated, intact cells
(Romanowsky stain)

Hürthle cell lesion:

Hürthle cells

Hürthle cells in loose monolayered sheets

Hürthle cell adenoma (Pap)

Hürthle cell adenoma - Diff-Quik

Hürthle cell adenoma (Pap)

Back to top