Table 2.

Incidence and common ultrasonographic features of the PTC variants

Variant	Incidence	Common ultrasonographic feature
Tall cell variant	4%-17% of PTCs	Typical malignant featuresa), frequent nodal metastasis
Columnar cell variant	No report	Typical malignant features vs. circumscribed border
Hobnail variant	No report	Typical malignant features, frequent nodal metastasis
Solid variant	3% of PTCs	Typical malignant features vs. circumscribed border
Diffuse sclerosing variant	0.7%-6.6% of PTCs	Ill-defined mass, scattered microcalcifications, nodal metastasis
Follicular variant (encapsulated)	10%-20% of all thyroid cancers	Solid hypoechoic or isoechoic nodule
Cribriform-morular variant	1% of FAP patients	Solid oval to round nodule without calcification
Warthin-like variant	No report	Benign-looking nodule, heterogeneous parenchyma

PTC, papillary thyroid carcinoma; FAP, familial adenomatous polyposis.

^a)Typical malignant features include a solid hypoechoic nodule with microcalcification, a spiculated/microlobulated margin, or nonparallel orientation.