Low power: DQ stain
Hypercellular smear with predominantly flat sheeted cohesive clusters
Lack of single cells
High power: DQ stain
Rare papillary fragment with fibrovascular core
Low power: Pap Stain
Cellular swirls forming abstract shapes
Note oncocytoid cells in the lower right and multinucleated giant cell upper left corner
High power: DQ stain
Note the nuclear enlargement, nuclear crowding, nuclear overlap and pseudoinclusions
High power: Pap stain
Nuclear changes: nuclear irregularity, small nucleoli, nuclear overlap, rare grooves and pseudoinclusions
High power: Pap stain
Nuclear changes: Prominent nuclear grooves in this example. Note nuclear enlargement and irregularity are more reliable diagnostic criteria
High power: DQ stain
Multinucleated giant cell (left mid) and fragment with oncocytoid cells (lower left) with a classic flat sheeted fragment (right)
High power: Pap stain
Thick (bubble-gum) colloid
Swirling sheet with squamoid morule-like features. Note nuclear pseudoinclusions
Features
• High cellularity
• Cohesive clusters
• Predominantly flat sheets
• Papillary fragments with true fibro-vascular cores (uncommon)
• Cellular swirls
• Squamoid and/or oncocytoid cell populations
• Syncytium-like arrangement (rather than follicles; except follicular variant)
• Nuclear enlargement, as compared to background normal follicles or lymphocytes
• Nuclear overlapping and crowding
• Nuclear membrane irregularity
• Chromatin clearing
• Nuclear grooves
• Nuclear pseudo-inclusions (sensitive but not specific)
• Occasional small nucleoli
• Minimal thick colloid; except rare colloid rich variants (see colloid rich variant for details)
• Multinucleated giant cells and hemosiderin laden macrophages
• Rare mitoses
• Rare apoptosis
• Rare necrosis
• Express cytokeratin, Pax-8, TTF-1, thyroglobulin, Galectin-3
Szporn A et al. Mod Pathol. 2006 Nov;19(11):1470-3.