Assessment of thyroid lesions (general)

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Assessment of thyroid lesions is commonly encountered in radiological practice.

Thyroid mass

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

Risk factors for malignancy

young
male
solitary
cold on thyroid scan
past history of radiotherapy

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

Radiographic features

Ultrasound

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)

Nuclear medicine

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

Treatment and prognosis

Indications for FNA

The criteria developed by the American Thyroid Association (2015) ¹¹ are often used in clinical practice. See: ATA guidelines for assessment of thyroid nodules.

Indications for FNA according to Society of Radiologists in Ultrasound (2008) ⁴

nodule ≥1.0 cm at the largest diameter if microcalcifications are present
nodule ≥1.5 cm if the nodule is solid or if there are coarse calcifications within the nodule

Additional recommendations for FNA by the American Association of Clinical Endocrinologists ⁴:

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

Management of FNA results

benign: clinical and imaging follow-up
follicular neoplasm
- require excisional biopsy because of overlap between
  - hyperplastic nodule
  - follicular adenoma
  - follicular carcinoma
  - follicular variant of papillary carcinoma
atypia of uncertain significance / follicular lesion of uncertain significance (AUS/FLUS)
- 3-6%
- repeat FNA
  - two samples obtained at second biopsy
  - if AUS/FLUS again (~20%) on the first sample, then the risk of malignancy is 5-15% ¹⁰
  - the second sample may be sent for gene sequencing, if available (gene expression classifier)
    - if benign, then normal clinical and imaging follow-up
    - if suspicious, 50% risk of malignancy
malignant: partial or total thyroidectomy with lymph node exploration

Staging

see: thyroid cancer staging

~~-<a href="/articles/medullary-thyroid-cancer">medullary</a>: 5%</li>~~
+<a href="/articles/medullary-thyroid-carcinoma-1">medullary</a>: 5%</li>
~~-<li>cold on <a title="Thyroid scan (I-123)" href="/articles/thyroid-scan-i-123">thyroid scan</a>~~
+<li>cold on <a href="/articles/thyroid-scan-i-123">thyroid scan</a>
~~-</ul><h5>Staging</h5><ul><li>see: <a href="/articles/thyroid-cancer-staging-1">thyroid cancer staging</a>~~
+</ul><h5>Staging</h5><ul><li>see: <a href="/articles/differentiated-thyroid-cancer-staging">thyroid cancer staging</a>

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