| Major Features |
| Encapsulation or clear demarcation |
| Follicular growth pattern |
| Nuclear features of papillary thyroid carcinoma (PTC)a: |
| Enlargement, crowding/overlapping |
| Elongation |
| Irregular contours |
| Grooves |
| Pseudoinclusionsb |
| Chromatin clearingc |
| Minor Features |
| Dark colloid |
| Irregularly shaped follicles |
| Intratumoral fibrosis |
| “Sprinkling” signd |
| Follicles cleft from stromad |
| Multinucleated giant cells within follicles |
| Features Not Seen/Exclusion Criteria |
| “True” papillaee >1% |
| Psammoma bodies |
| Infiltrative border |
| Tumor necrosis |
| High mitotic activityf |
| Cell/morphologic characteristics of other variants of PTCg |
a
In a tumor with multifocal presence of PTC, most pathologists do not require a specific minimal percentage of the tumor nodule to demonstrate these features.
b
A major and helpful diagnostic feature for all variants of PTC, although uncommon in EFVPTC.
c
Effacement of normal chromatin distribution with margination of chromatin to membrane also known as “glassy nuclei” or “Orphan Annie” nuclei.
d
As described and illustrated by Vanzati et al.21
e
True papillae are defined as complex, arborizing papillae with fibrovascular cores, lined by cells with nuclear features of PTC, and not associated with a fine-needle aspiration area.
f
At least 3 per 10 high-power fields (×40).
g
Such as tall cell features, cribriform-morular variant, solid variant, etc.