Table 1.

Diagnostic categories of thyroid core needle biopsy

I. Nondiagnostic or unsatisfactory
	Non-tumor adjacent thyroid tissue only
	Extrathyroid tissue only (e.g., skeletal muscle, mature adipose tissue)
	Acellular specimen (e.g., acellular fibrotic tissue, acellular hyalinized tissue, cystic fluid only)
	Blood clot only
	Other
II. Benign lesion
	Benign follicular nodule
	Hashimoto’s thyroiditis
	Subacute granulomatous thyroiditis
	Nonthyroidal lesion (e.g., parathyroid lesions, benign neurogenic tumors, benign lymph node)
	Other
III. Indeterminate lesion
	IIIa. Indeterminate follicular lesion with nuclear atypia
	IIIb. Indeterminate follicular lesion with architectural atypia
	IIIc. Indeterminate follicular lesion with nuclear and architectural atypia
	IIId. Indeterminate follicular lesion with Hürthle cell changes
	IIIe. Indeterminate lesion, not otherwise specified
IV. Follicular neoplasm
	IVa. Follicular neoplasm, conventional type
	IVb. Follicular neoplasm with nuclear atypia
	IVc. Hürthle cell neoplasm
	IVd. Follicular neoplasm, not otherwise specified
V. Suspicious for malignancy
	Suspicious for papillary thyroid carcinoma, medullary thyroid carcinoma, poorly differentiated thyroid carcinoma, metastatic carcinoma, lymphoma, etc.
VI. Malignant
	Papillary thyroid carcinoma, poorly differentiated thyroid carcinoma, anaplastic thyroid carcinoma, medullary thyroid carcinoma, lymphoma, metastatic carcinoma, etc
Comments:
	1. The core needle biopsy provides an accurate diagnosis in most cases; however, it may miss some cancers or sometimes may be inconclusive.
	2. Definitive therapeutic surgery (i.e., a total thyroidectomy) should not be undertaken as a result of a category III, IV, or V core needle biopsy diagnosis.
	3. The management of a thyroid lesion must be based on a multidisciplinary approach.
	4. In the category IIIc or IVb, some nuclear features raise the possibility of a noninvasive follicular thyroid neoplasm with papillary-like nuclear features or an invasive follicular variant of papillary thyroid carcinoma; definitive distinction among these entities is not possible on biopsy material.