I. Nondiagnostic or unsatisfactory |
• Normal thyroid tissue only |
• Extrathyroid tissue only (e.g., skeletal muscle, mature adipose tissue) |
• A virtually acellular specimen |
• Acellular/paucicellular fibrotic nodule |
• Blood clot only |
• Other |
II. Benign lesion |
• Benign follicular nodule or consistent with a benign follicular nodule |
• Hashimoto's thyroiditis |
• Granulomatous (subacute) thyroiditis |
• Nonthyroidal lesion (e.g., parathyroid lesions, benign neurogenic tumors, benign lymph node) |
• Other |
III. Indeterminate lesion |
IIIA. Indeterminate follicular lesion with nuclear atypia |
• Follicular proliferative lesions with focal nuclear atypia |
• Follicular proliferative lesions with equivocal or questionable nuclear atypia |
• Atypical follicular cells embedded in a fibrotic stroma |
IIIB. Indeterminate follicular lesion with architectural atypia |
• Microfollicular proliferative lesion lacking a fibrous capsule or the adjacent nonlesional tissue in the specimen |
• Solid or trabecular follicular lesion lacking a fibrous capsule or the adjacent nonlesional tissue in the specimen |
• Macrofollicular proliferative lesion with a fibrous capsule |
• Hürthle cell proliferative lesion lacking a fibrous capsule or the adjacent nonlesional tissue in the specimen |
IIIC. Other indeterminate lesions |
IV. Follicular neoplasm or suspicious for a follicular neoplasm |
• Microfollicular proliferative lesion with a fibrous capsule |
• Mixed microfollicular and normofollicular proliferative lesion with a fibrous capsule |
• Solid/trabecular follicular proliferative lesion with a fibrous capsule |
• Hürthle cell proliferative lesion with a fibrous capsule |
• Follicular neoplasm with focal nuclear atypia |
V. Suspicious for malignancy |
• Suspicious for papillary carcinoma, medullary carcinoma, poorly differentiated carcinoma, metastatic carcinoma, lymphoma, etc. |
VI. Malignant |
• Papillary thyroid carcinoma, poorly differentiated carcinoma, undifferentiated (anaplastic 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. |