Management of Solitary Thyroid Nodule - Cummings (Fig. 122.9)

Step-by-Step Breakdown of the Algorithm

Step 1 - History & Physical Examination (Hx/PE)

• Age < 20 years or elderly male
• History of head/neck radiation
• Rapid nodule growth
• Compressive/invasive symptoms: hoarseness, dysphagia, dyspnea
• Fixation of the nodule
• Family history of thyroid carcinoma, MEN syndrome

Step 2 - Initial Workup: TSH + FNAC + Ultrasound (US)

Step 3 - Branch by TSH Status (before FNAC in certain cases)

Step 4 - Branch by FNAC Result

A. Carcinoma (diagnostic/strongly suggestive)

• → Surgery (well-differentiated thyroid carcinoma)
• Anaplastic carcinoma and lymphoma require additional workup to determine treatment modality

B. Follicular Neoplasm

• Cannot distinguish adenoma from carcinoma on FNAC alone (capsular/vascular invasion needed)
• If TSH normal/high → Surgery
• If TSH low → Radionuclide scan:
  • Cold nodule → Surgery
  • Hot nodule → Evaluate and treat for thyrotoxicosis

C. Benign

• → Observe (close clinical and US monitoring)
• If nodule grows → consider surgery

D. Indeterminate (15-30% of FNA specimens)

• → Repeat FNAC (preferably US-guided)
• Molecular marker testing options:
  • Afirma Gene Expression Classifier - high NPV (93%), best as "rule-out" test
  • ThyroSeq - high NPV (~95%), also a "rule-out" test
  • ThyGenX/ThyraMIR - highest PPV (~66%), used as "rule-in" test
• Atypia/follicular lesion of undetermined significance (AUS/FLUS): 5-10% malignancy risk

Key Points from Cummings

• Only ~5% of thyroid nodules are carcinoma; ~1 in 200 is lethal
• Palpable nodules ≥ 1 cm warrant full workup
• Radionuclide scanning is not routinely done; reserved for hyperthyroid patients or post-indeterminate FNAC
• Ultrasound guidance should be used for repeat FNAC after indeterminate results
• Surgery is indicated for well-differentiated thyroid carcinoma; anaplastic carcinoma and lymphoma need additional assessment

Management of Thyroid Nodule with Low TSH (Suppressed TSH)

Why TSH Matters First

Step-by-Step Management (Cummings Algorithm)

Thyroid Nodule + LOW TSH
         ↓
  Radionuclide Scan
  (¹²³I or ⁹⁹ᵐTc pertechnetate)
         ↓
   ┌─────────────────┐
   ↓                 ↓
 HOT nodule       COLD nodule
(hyperfunctioning)  (non-functioning)
   ↓                 ↓
Evaluate and     Surgery
treat for
thyrotoxicosis

HOT Nodule (Autonomously Hyperfunctioning)

• Concentrates tracer on scan; suppresses rest of gland
• Virtually never malignant - FNAC is not required
• Treat the thyrotoxicosis:
  • Antithyroid drugs (carbimazole/methimazole) for symptom control
  • Radioactive iodine (¹³¹I) - definitive therapy
  • Surgery (thyroid lobectomy) - if large nodule, compressive symptoms, or patient preference
• Also called Marine-Lenhart syndrome when a functioning nodule coexists with Graves disease

COLD Nodule (Non-Functioning) in Low-TSH Patient

• Does not concentrate tracer
• Higher malignancy risk than hot nodule
• → Surgery is indicated (proceed as per follicular neoplasm pathway)
• FNAC may be performed pre-operatively to guide surgical extent

Additional Notes from Cummings

• ¹²³I is preferred over ⁹⁹ᵐTc because it provides a true measure of iodine uptake, not just trapping
• ⁹⁹ᵐTc is cheaper and faster (no 2-day wait) but does not confirm organification
• Radionuclide scanning is not part of routine nodule evaluation - it is reserved specifically for the low TSH scenario (or post-indeterminate FNAC)
• The combination of low TSH + FNAC results can be misleading if done in sequence incorrectly - always scan first in the hyperthyroid patient

Does the Thyroid Gland Have a True and False Capsule?

1. True Capsule (Internal / Fibrous Capsule)

• A thin, densely adherent fibrous layer that is derived from the stroma of the gland itself
• Closely applied to and inseparable from the thyroid parenchyma
• Sends vascularized connective tissue septa inward, dividing the gland into pseudolobules (larger and smaller lobules)
• At the posteromedial surface, it condenses to form Berry's ligament (posterior suspensory ligament), which attaches the gland firmly to the cricoid cartilage and upper 2-3 tracheal rings
• Because of this firm attachment via Berry's ligament, the thyroid moves with swallowing

2. False Capsule (External / Surgical Capsule)

• Formed by the pretracheal layer of the deep cervical fascia (middle layer of cervical fascia) - it is NOT a true capsular structure of the gland itself
• Tougher than the true capsule
• Also called the "surgical capsule" because it defines the plane of dissection during thyroidectomy

The Space Between the Two Capsules

"The space between the loosely adherent capsular layers is filled with loose connective tissue and contains larger branches of vessels, as well as the parathyroid gland in its posterior portion."

• Color Atlas of Human Anatomy, Vol. 2

Clinical Significance

• Extrathyroidal extension in thyroid cancer is defined as tumor breaching the true capsule
• T3b staging = invasion beyond the true capsule into strap muscles
• T4a = invasion through the false capsule into surrounding structures (larynx, trachea, esophagus, RLN)