Tables and Figures
28
Table 2. Pathologic Diagnostic Criteria of NIFTP
• Encapsulation or clear demarcation
a
• Follicular growth pattern, including :
▶ Absent papillae
b
▶ Absent psammoma bodies (reminiscent of dead papillae)
▶ <30% solid, trabecular, or insular growth pattern
• Nuclear features of papillary thyroid carcinoma
• No invasive characteristics (no capsular or vascular invasion)
b
• No tumor necrosis
• No high mitotic activity, defined as <3 mitoses per 10 high-power field
a
Tumors are well demarcated from the surrounding thyroid parenchyma and can be thinly or
partially encapsulated.
b
Features requiring histopathologic examination of the entire tumor capsule and tumor.
Table 3. WHO Pathologic Classification of Differentiated
Thyroid Carcinoma (WHO, 5 Edition)
Follicular cell-derived
neoplasms
Subtypes
Low-risk neoplasms
1. NIFTP
a,b
2. Follicular Tumor of Uncertain Malignant Potential
3. Hyalinizing Trabecular Tumor
Malignant neoplasms 1. Follicular Thyroid Carcinoma
a. Minimally invasive
b. Encapsulated angioinvasive
c. Widely invasive
2. Invasive encapsulated follicular variant papillary carcinoma
3. Papillary thyroid carcinoma – subtypes
a. Classic
b. Encapsulated classic
c. Infiltrative follicular
d. Tall Cell
e. Columnar Cell
f. Hobnail
g. Diffuse Sclerosing
h. Solid/Trabecular
i. Warthin-Like
j. Oncocytic
k. Others
c
4. Oncocytic Carcinoma
a. Minimally invasive
b. Encapsulated Angioinvasive
c. Widely invasive
