Diagnostic category |
Risk of thyroid cancer |
Most common histologic diagnoses |
Indications for repeated FNB |
Commonly recommended managementa |
I: Nondiagnostic biopsy |
5%-10%c,d |
Any diagnosis possible |
Repeated FNB with US guidance, usually in 3-12 months, depending on risk; in case of clinical suspicion of anaplastic cancer, further diagnostics must be continued immediately |
Indications for surgery depend on clinical risk of malignancy; nondiagnostic biopsy likely in patients with cysts or thyroiditis |
II: Benign |
0%-3%c,d |
Multinodular goiter, including hyperplastic nodules and colloid nodules; thyroiditis |
No (except in cases of new US risk factors of suspicious lymphadenopathy) |
Follow-up (clinical and US) |
III: AUS or FLUS |
6%-18%c (10%-30%)d |
Category used only if accurate cytologic diagnosis not possible |
Yes (in 3-12 months, depending on risk) |
Possible options: (1) molecular testing (if available); (2) active surveillance; (3) surgery
|
IV: Suspicious for follicular neoplasma |
10%-40%b,c (25%-40%)d |
May reflect nonneoplastic lesion or benign tumor, which cannot be differentiated from malignancy by cytology alone |
No but if surgery is planned diagnosis must be confirmed by another cytologist |
Possible options: (1) molecular testing (if available); (2) active surveillance; (3) surgery |
V: Suspicious for malignancy |
45%-60%c (50%-75%)d |
Suspected thyroid cancer |
No but diagnosis must be confirmed by another cytologist |
Surgery |
VI: Malignant |
94%-96%c (97%-99%)d |
Papillary thyroid cancer; medullary thyroid cancer; anaplastic thyroid cancer; other malignancy |
No but diagnosis must be confirmed by another cytologist |
Surgery |
a Actual management also depends on other clinical and US risk factors. b The diagnosis of nodules “suspicious for follicular neoplasm” includes those “suspicious for oxyphil neoplasm,” which is more frequently an unequivocal indication for surgery. c Risk of malignancy if NIFTP is excluded because it is benign; previously classified as noninvasive follicular variant of papillary thyroid carcinoma. d Risk of malignancy if NIFTP is included. | ||||
Based on Thyroid. 2017;27(11):1341-1346 and Endokrynol Pol. 2018;69(1):34-74. | ||||
↑, increase; ↓, decrease; AUS, atypia of undetermined significance; FLUS, follicular lesion of undetermined significance; FT3, free triiodothyronine; FT4, free thyroxine; NIFTP, noninvasive follicular thyroid neoplasm with papillary-like nuclear features; TSH, thyroid-stimulating hormone; US, ultrasound. |