6.2.11: 11. Diagnostic Procedures

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Wayne’s Index to Determine Hyperthyroidism

FNAC: Bethesda System for Risk of Malignancy

Clinical Indications for FNAC

Suspicious clinical findings: Rapidly growing, firm mass, thyroid asymmetry, cervical lymphadenopathy, recent onset hoarseness/ vocal cord paralysis
Palpable firm thyroid nodule: FNAC of thyroid nodule
Palpable firm cervical lymph node: FNAC of node +/- thyroid nodule
Factors that may be considered in addition to above suspicious clinical findings: Prior thyroid cancer, radiation exposure, 1st degree relative with thyroid cancer of MEN2, FDG avid on PET scan, thyroid cancer associated history e.g. familial adenomatous polyposis, Carney complex, Cowden syndrome.
If FNAC not indicated, repeat exam after 6-12 months; if stable for 1-2yrs, then consider review at 3-5 yearly intervals

Ultrasound Indications for FNAC

U/S can be used to risk-stratify using the Thyroid Imaging Reporting and Data System (TI-RADS) (http://tiradscalculator.com /)

Solid nodule

With suspicious sonographic features >1.0 cm
Without suspicious sonographic features >1.5 cm

Mixed cystic-solid nodule

With suspicious sonographic features: hypoechoic,
microcalcifications, infiltrative margins, taller
than wide in transverse plane Solid component >1.0 cm
Without suspicious sonographic features: Spongiform
nodules, isoechoic of hyperechoic solid nodules, mixed
solid-cystic nodules without above suspicious features Solid component >1.5 cm

Spongiform nodule (multiple microcystic components
in >50% of volume of nodule >2.0 cm

Suspicious cervical lymph node: FNAC of node +/- thyroid nodule

If FNAC not indicated, then repeat US after 6-12 months; if stable for 1-2yrs, then consider US at 3-5 yearly intervals

Above criteria are general guidelines: With high risk clinical features, evaluation of smaller nodules may be indicated based on clinical concerns e.g. prior thyroid cancer, radiation exposure, 1st degree relative with thyroid cancer of MEN2, FDG avid on PET scan, thyroid cancer associated history e.g. familial adenomatous polyposis, Carney complex, Cowden syndrome.

TI-RADS Calculator

Calculates TI-RADS Score

Clinical Indications for Diagnostic Thyroid Surgery in Absence of U/S and FNAC

Suspicious clinical mass: Rapidly growing, firm mass, thyroid asymmetry, cervical lymphadenopathy, recent onset hoarseness/ vocal cord paralysis
Palpable firm cervical lymph node
In addition to above suspicious clinical findings: Prior thyroid cancer, radiation exposure, 1st degree relative with thyroid cancer of MEN2, FDG avid on PET scan, thyroid cancer associated history e.g. familial adenomatous polyposis, Carney complex, Cowden syndrome
When referral is not possible for U/S or FNAC

U/S Indications for Diagnostic Thyroid Surgery in Absence of FNAC

U/S can be used to risk-stratify using the Thyroid Imaging Reporting and Data System (TI-RADS) (http://tiradscalculator.com/)

Solid nodule

With suspicious sonographic features >1.0 cm
Without suspicious sonographic features >1.5 cm

Mixed cystic-solid nodule

With suspicious sonographic features: hypoechoic, Solid component >1.0 cm
microcalcifications, infiltrative margins, taller than
wide in transverse plane
Without suspicious sonographic features: Spongiform Solid component >1.5 cm
nodules, isoechoic of hyper echoic solid nodules, mixed
solid-cystic nodules without above suspicious features

Spongiform nodule (multiple microcystic components >2.0 cm
in >50% of volume of nodule

Suspicious cervical lymph node: May consider biopsy of lymph node

Diagnostic Nodulectomy vs. Thyroid Lobectomy

In the absence of a cytologic diagnosis of a thyroid nodule, and when clinically indicated to obtain a histopathologic diagnosis, the question arises whether one should perform a nodulectomy or thyroid lobectomy. Even though thyroid lobectomy is the standard of care, at least 25%* of lobectomy patients will require long-term thyroid replacement therapy.

Thyroid lobectomy
- Therapeutic for some differentiated cancers
- Ipsilateral revision surgery not required
Nodulectomy
- Consider only if patients do not have access to thyroid replacement
- Nodulectomy ideal for isthmus nodules, or nodules located along the anterior/inferior aspect of the thyroid lobe
- If nodule situated deeply/posterior in gland, then one should identify the RLN prior to the nodulectomy to avoid injuring the RLN
- May need to do completion lobectomy depending on histology of nodule, with increased risk to RLN associated with revision surgery

* Ahn D, Sohn JH, Jeon JH. Hypothyroidism Following Hemithyroidectomy: Incidence, Risk Factors, and Clinical Characteristics J Clin Endocrinol Metab. 2016 Apr;101(4):1429-36. https://doi.org/10.1210/jc.2015-3997

* Said M, Chiu V, Haigh PI. Hypothyroidism after hemithyroidectomy. World J Surg. 2013 Dec;37(12):2839-44 https://www.ncbi.nlm.nih.gov/pubmed/23982782