- 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
- 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)
- 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)
- Primary malignant tumor (papillary, high grade microfollicular, insular, medullary or anaplastic carcinoma; lymphoma)
- 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
- Thyroiditis (acute, Hashimoto's, subacute)
- Other (Graves' disease, metastatic carcinoma)
- 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
Cytodiagnostic groups with common nodular lesions
- 70 year old man with diffuse large B-cell lymphoma misdiagnosed as anaplastic carcinoma (Cytojournal 2006;3:23)
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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
Benign epithelial cells, colloid, macrophages
Thin prep 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)
Follicular neoplasms:
FNA: follicular neoplasm, excision: follicular adenoma
FNA: suspicious for
papillary carcinoma,
excision: follicular
variant of papillary
carcinoma
Epithelial cells in follicular
arrangement suggesting
adenoma, but which could
be from a follicular 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)
Suspicious for papillary carcinoma:
Rare intranuclear inclusions and abundant colloid
Cellular with
papillary formation,
nuclear inclusions
and grooves
