Is a thyroid ultrasound (US) indicated for a patient with a family history of thyroid cancer?

Thyroid Ultrasound for Family History of Thyroid Cancer

Thyroid ultrasound screening is NOT routinely indicated for patients with a family history of thyroid cancer, with the critical exception of familial nonmedullary thyroid carcinoma (FNMTC) or hereditary syndromes like familial adenomatous polyposis (FAP) and MEN2, where annual screening is specifically recommended. 1, 2

General Population Screening: Not Recommended

• Ultrasound should not be used as a general screening tool for thyroid cancer, even in patients with family history, as it is recognized as the most important driver of thyroid cancer overdiagnosis 3
• The US Preventive Services Task Force found no fair- to good-quality evidence that thyroid cancer screening decreases mortality rates or improves patient health outcomes 4
• Population-based screening leads to identification of indolent thyroid cancers, and treatment of these overdiagnosed cancers increases the risk of patient harms without mortality benefit 4
• In a study of 429 obese patients evaluated for thyroid cancer risk factors including family history, the presence of family history did not confer an increased risk for thyroid nodules requiring biopsy (no risk factors 16.6% vs. risk factors 14.1%, P = .64) 5

Specific High-Risk Syndromes: Screening IS Indicated

Familial Adenomatous Polyposis (FAP)

• Annual cervical ultrasonography should be considered starting at age 25 to 30 years in patients with classic FAP or attenuated FAP 1
• This recommendation applies to confirmed mutation carriers in the APC gene 1

Familial Nonmedullary Thyroid Carcinoma (FNMTC)

• Screening with neck ultrasonography is specifically recommended for symptom-free family members of patients with FNMTC 2
• In a study of 149 family members from 53 FNMTC families, ultrasonographic screening detected thyroid cancer in 10.1% of subjects, with 47% having intraglandular metastases and 43% having lymph node metastases despite being asymptomatic 2
• FNMTC is a distinct clinical entity with high incidence of multifocality, association with multiple benign nodules, and shorter disease-free survival due to frequent locoregional recurrence 2

Multiple Endocrine Neoplasia Type 2 (MEN2)

• Annual ultrasound and serum calcitonin screening starting at age 3 years for children with "high-risk" RET alleles (codons 634 and 883), with thyroidectomy when elevated calcitonin is detected or at age 5 years 1
• For "moderate-risk" alleles, annual surveillance with serum calcitonin and thyroid ultrasound may be pursued with prophylactic surgery offered when there is suspicion for progression 1

Critical Distinction: Sporadic vs. Syndromic Family History

The key clinical decision point is determining whether the family history represents:

• Sporadic familial thyroid cancer (one or two relatives with differentiated thyroid cancer): No screening ultrasound recommended 3, 4
• FNMTC (three or more first-degree relatives with nonmedullary thyroid cancer): Annual ultrasound screening recommended 2
• Hereditary cancer syndromes (FAP, MEN2): Protocol-driven surveillance as outlined above 1

When to Order Ultrasound in Patients with Family History

Ultrasound is appropriate when:

• A palpable thyroid nodule is detected on physical examination (≥1 cm) 6
• The patient has symptoms suggestive of thyroid disease (compressive symptoms, voice changes) 6
• The patient has a confirmed diagnosis of FAP, FNMTC, or MEN2 as part of surveillance protocols 1, 2
• The patient has additional high-risk features beyond family history, such as history of head and neck irradiation (which increases malignancy risk approximately 7-fold) 7

Common Pitfalls to Avoid

• Do not order screening ultrasound for simple family history (one affected relative) without other indications, as this leads to overdiagnosis of clinically insignificant papillary microcarcinomas 3, 4
• Do not assume all family history is equal: Take a detailed family history to distinguish sporadic cases from true hereditary syndromes 2
• Do not rely on palpation alone in confirmed high-risk populations (FNMTC, post-radiation): ultrasound demonstrated 100% sensitivity compared to 12.5% for palpation in high-risk childhood cancer survivors 7
• Recognize that surgical harms are real: permanent hypoparathyroidism occurs in 2.12-5.93 per 100 thyroidectomies, and recurrent laryngeal nerve palsy in 0.99-2.13 per 100 operations 4