Assessment of thyroid lesions (general)

Assessment of thyroid lesions is commonly encountered in radiological practice.

hyperplastic/colloid nodule/nodular hyperplasia: 85%
adenoma
- follicular: 5%
- others: rare
carcinoma
- papillary: 60-80% of carcinomas
- follicular: 10-20%
- medullary: 5%
- anaplastic: 1-2%
- thyroid lymphoma: 1%
- metastases to the thyroid: 1%
others
- fat-containing thyroid lesions
  - adenolipoma of the thyroid gland
  - liposarcoma of the thyroid gland

The first three risk factors are really a reflection that elderly women with multiple benign thyroid nodules are very common.

taller-than-wide in axial/transverse dimension, microcalcifications, local invasiveness, microlobulated contour, and hypoechogenicity are suspicious features
size criteria are controversial and continuously evolving
cervical lymphadenopathy is a feature
for detailed assessment, see: assessment of thyroid lesions (ultrasound)

A single 'cold' nodule has a 10% chance of being malignant. A single 'hot' nodule has <1% chance of being malignant.

Each grading system provides recommendations for when FNA is indicated (see snippet for individual systems).

Both appearance and size are factors to consider.

The criteria developed by the American Thyroid Association (2015) are often used in clinical practice. See: ATA guidelines for assessment of thyroid nodules.

The ACR TI-RADS system recommends FNA for TR3 lesions >25 mm, TR4 lesions >15 mm and TR5 lesions >10 mm .

The BTA U classification recommends FNA for any non-benign lesion (i.e. U3, U4 or U5) .

Additional recommendations for FNA by the American Association of Clinical Endocrinologists :

FNA recommended for nodules <10 mm whenever clinical information or ultrasound features raises suspicion about the presence of a malignancy