Low power: DQ stain
Cellular aspirate with uniform follicular cells in crowded clusters and microfollicles
Note lack of colloid in the background
Note: microfollicles are defined as 6-12 crowded cells in a 2D ring/rosette-like formation, with or without colloid in the center
Medium power: DQ stain
Cellular aspirate with follicular cells with slight variation in size in a predominantly microfollicular arrangement
Medium power: DQ stain
Cellular aspirate with follicular cells with slight variation in size, in microfollicles, crowded clusters and as single cells
Low power: Pap stain
Cellular aspirate with numerous follicular cells in a predominant microfollicular pattern
Note lack of colloid in the background
Medium power: Pap stain
Follicular cells with slight variation in size, round nuclei, even chromatin, inconspicuous nucleoli and pale cytoplasm, in microfollicles, crowded clusters and single cells
Medium power: Pap stain
Markedly cellular smear with follicular cells in syncitial aggregates, microfollicles, crowded clusters and single cells
Medium power: Pap stain
Follicular cells with slight variation in size, nuclear atypia and overlapping, in small crowded clusters, microfollicular pattern and single cells
Medium power: Pap stain
Follicular cells with slight variation in size, some nuclear atypia, even chromatin, inconspicuous nucleoli, and pale cytoplasm, in microfollicular pattern and single cells
Note rare nuclear grooves and suggestive intranuclear cytoplasmic inclusions raising concern for FVPTC
Medium power: Pap stain
Follicular cells with slight variation in size, some nuclear atypia, even chromatin, inconspicuous nucleoli, and pale cytoplasm, in microfollicular pattern and single cells
High power: Pap stain
Follicular cells with variation in size, nuclear atypia, even chromatin, inconspicuous nucleoli, and pale cytoplasm, in small crowded clusters, microfollicular pattern and single cells
Note rare nuclear grooves and suggestive intranuclear cytoplasmic inclusions raising concern for FVPTC
Features
• Moderate to marked cellularity
• Microfollicular architecture predominates
• Crowded clusters
• May have single cells
• Normal to enlarged follicular cells
• Pale scant cytoplasm
• Nuclei round, may be enlarged
• Nuclear atypia may be present
• Evenly dispersed chromatin
• Inconspicuous to small to prominent nucleoli
• May have irregular nuclei and nuclear grooves (FVPTC) (see note)
• May have intranuclear cytoplasmic inclusions (FVPTC) (see note)
• May have fine powdery chromatin (FVPTC) (see note)
• Colloid scant to absent
• D/D of follicular neoplasm includes follicular adenoma, follicular carcinoma (histologic evidence of invasion or metastasis) or a follicular variant of papillary thyroid carcinoma (FVPTC).
• Express cytokeratin, CK7, Pax-8, TTF-1, thyroglobulin
Lin JD et al. Acta Cytol. 1997 May-Jun;41(3):687-91.
Baloch ZW et al. Diagn Cytopathol. 2002 Jan;26(1):41-4.