Thyroid Nodules Assessment
U-Classification, FNAC & Malignancy Risk Stratification
Key Clinical Points
- • FIRST STEP: Check TSH before ultrasound — if suppressed, get thyroid scan first
- • Hot nodules have <1% malignancy risk — FNAC generally NOT needed
- • U4/U5 nodules >1 cm: FNAC recommended
- • Thy3f (follicular neoplasm): diagnostic hemithyroidectomy required
- • Rapid growth, fixed lymph nodes, or vocal cord palsy = urgent cancer pathway
BTA U-Classification & FNAC Thresholds
| U-Score | Description | FNAC Threshold | Malignancy Risk |
|---|---|---|---|
| U1 | Normal | Not indicated | ~0% |
| U2 | Benign (cystic, spongiform) | Not indicated | <1% |
| U3 | Indeterminate | >2 cm (or 1-2 cm per protocol) | 5-15% |
| U4 | Suspicious | >1 cm | 15-30% |
| U5 | Malignant features | >1 cm (consider 5-10 mm) | >50% |
FNAC Thy Classification & Management
| Thy Class | Description | Malignancy Risk | Management |
|---|---|---|---|
| Thy1 | Non-diagnostic | Varies | Repeat FNAC; core biopsy if 2x Thy1 |
| Thy2 | Benign | <3% | Reassure; monitor if discordant |
| Thy3a | Atypia of undetermined significance | ~25% | Repeat FNAC |
| Thy3f | Follicular neoplasm | ~31% | Diagnostic hemithyroidectomy |
| Thy4 | Suspicious for malignancy | ~68% | MDT discussion; usually surgery |
| Thy5 | Malignant | >99% | MDT discussion; surgery planned |
Urgent Cancer Pathway Referral Criteria
- • Vocal cord palsy with thyroid nodule
- • Rapidly enlarging thyroid mass
- • Fixed cervical lymphadenopathy
- • Stridor or airway compromise
- • Age <20 or >60 with new nodule + risk factors
- • History of head/neck radiation
Demographics
Age affects presentation and management approach
Thyroid disease 4-8x more common in females
Pregnancy significantly alters management approach
Symptoms
Primary presenting complaint
May indicate compressive symptoms
Red flag - possible recurrent laryngeal nerve involvement
Red flag for malignancy
Compressive symptoms requiring urgent evaluation
Risk Factors
Increased risk of autoimmune thyroid disease
Increased malignancy risk
Significant risk factor for thyroid malignancy
Associated with autoimmune thyroid disease
Affects etiology and management
Medications
Multiple drugs affect thyroid function
Can cause thyrotoxicosis or interfere with RAI uptake