Thyroid Nodules and Thyroid Cancer

Dr. Boyd Lee Otolaryngology – Head and Neck

Surgery Memorial University

Anatomy

Anatomy

• 2 lateral lobes connected by isthmus

• Pyramidal lobe 50% • Isthmus lies over 2nd –

3rd tracheal ring

Anatomy

• Blood supply – Superior and Inferior

thyroid a. – Superior, middle, and

inferior thyroid v.

Anatomy

• Lymphatic drainage – Prelaryngeal (delphian)

node – Pretracheal nodes – Paratracheal nodes – Lateral neck nodes

Thyroid Lymphatics

Anatomy

• Innervation – Parasympathetic via

vagus – Sympathetic via

cervical sympathetic chain

Anatomy • Recurrent Laryngeal

nerves – Lie in Tracheoesophageal

grooves adjacent to thyroid – Branches of Vagus n. – Left loops around aortic

arch – Right loops around right

subclavian a. – Innervates intrinsic muscles

of larynx except cricothyroid m.

Anatomy

• Parathyroid glands – Paired superior and

inferior parathyroid glands on posterior aspect of thyroid within thyroid capsule

Physiology

• Endocrine gland • Follicular cells

produce T4 and T3 • Parafollicular cells (C

cells) produce calcitonin

Thyroid Disorders

• Disorders of function – Hypothyroidism – Hyperthyroidism – Autoimmune

• Disorders of anatomy – Thyroid nodules

• Cysts • Adenomas • Carcinomas

– Goiter

Thyroid Nodules

• “Discrete lesion within the thyroid gland that is radiologically distinct from the surrounding thyroid parenchyma.”

• Not all palpable lesions correspond to a radiologically distinct abnormality

• Presence of a nodule(s) in the thyroid does not necessarily affect function of the gland

Thyroid Nodule

Thyroid Nodules

• Palpable thyroid nodules – 5% of women – 1% of males

• US detected nodules – 19-67% randomly selected individuals – Higher incidence in women and the elderly

• Generally, only nodules >1 cm need to be investigated unless other factors or SSx present

Thyroid Nodules • Only 6% of 1 cm nodules

are palpable • Only 50% of 1-2cm

nodules are palpable • Even 50-60% of >2 cm

nodules are not detected clinically

• Non-palpable nodules carry same risk of malignancy as palpable nodules

• Factors affecting the palpability of nodules – Size of nodule – Thickness of neck – Position of the nodule

(posterior, inferior, retro-sternal)

– Experience of the examiner

Thyroid Nodules

• 5-15% of thyroid nodules are malignant • Depends on:

– Age – Sex – Radiation exposure – Family history

Thyroid Cancer

• Well Differentiated – Papillary (85%) – Follicular (5%)

• Poorly Differentiated – Medullary (5%) – Anaplastic

• Other – Lymphoma – Sarcoma – Metastases

Thyroid Cancer

• Thyroid Cancer is one of 2 cancers that has an increasing incidence

• 3.6/100 000 in 1973 • 8.7/100 000 in 2002 • Increase is almost entirely due to papillary thyroid

ca (PTC) • Increase may be partly due to better detection • May also be secondary to increased radiation

esposure

Thyroid Nodule Workup

• Thorough History and Physical

Thyroid Nodule Workup

• History – Childhood neck radiation or

ionizing radiation exposure from fallout in childhood

– Total body irradiation for BMT or Hodgkins

– FHx of Thyroid Ca, MEN, Cowden, Gardner, or Werner syndromes.

– Rapid growth – Hoarseness

• Physical – Fixation of nodule – Vocal cord paralysis – Cervical adenopathy – > 1 cm

Thyroid Nodule Workup

• Thyroid Function studies – Serum TSH – If TSH is subnormal nuclear medicine scan is

ordered – No further workup necessary if the nodule is

hyperfunctioning (ie hot)

Thyroid Nodule Workup

• Diagnostic Imaging – Thyroid US should be performed in all patients

with known or suspected thyroid nodules

Thyroid Nodule Workup

• US findings suggesting a benign nodule – Purely cystic – Spongiform nodule

• US findings suggesting a malignant nodule – Hypoechogenicity – Increased intranodular

vascularity – Irregular infiltrative

margins – Microcalcifications – Absent halo – Shape taller than width in

transverse dimension

Thyroid US

Spongiform Nodule

Thyroid Cyst

Mixed Cyst

Papillary Ca

Papillary Ca

Fine Needle Aspiration Bx

• FNA is the most accurate and cost effective method for evaluating thyroid nodules.

• US guidance increases sensitivity and specificity of the FNA

Thyroid FNA

FNA Results

• Benign (5% risk of cancer) • Suspicious for Cancer (85% risk of Ca) • Cancer (95% risk of Ca) • Follicular Lesion • Atypical lesion of uncertain significance (5-

15% risk of Ca) • Non-diagnostic

Indications for Thyroid Surgery

• Cancer (Papillary, Follicular, Medullary) • Suspicion for, or risk of Cancer • Compressive Sx

– Dyspnea – Dysphagia

• Hyperthyroidism • Cosmesis

Pre-op/ Post-op Assessment

• Flexible laryngoscopy • US of lateral neck if Papillary Ca to

determine presence of lymphadenopathy + FNA Bx of any suspicious nodes

Papillary Thyroid Ca

• Females > males • Increased risk from radiation • Can be multi-focal • Lymphatic spread • Role of 131I treatment post -op • Excellent prognosis

– 97% 5 yr survival – 93% 10 yr survival – Prognosis better in age < 45, females

Follicular Thyroid Ca

• Cannot Dx on FNA • Dx made on vascular or capsular invasion • Hematogenous spread to lungs, bone • Role of 131I treatment post -op • Very good prognosis

– 91% 5 yr survival – 85% 10 yr survival

Medullary Thyroid Ca

• Arises from C cells • 25% of cases are genetic (MEN 2) • RET proto-oncogene • Calcitonin and CEA are makers • Presents with flushing/diarrhea • No role for 131I post op • 80% 5 yr survival • 75% 10 yr survival

Anaplastic Thyroid Ca

• Poorly differentiated • Highly aggressive • Can be difficult to distinguish from

thyroidal lymphoma • Surgical therapy includes open biopsy &

palliative tracheostomy • External beam radiation • Very poor prognosis

The Future of Thyroid Surgery

Summary

• Thyroid nodules are very common • Can be hard to palpate • More commonly diagnosed due to imaging

for other reasons (incedentalomas) • Thyroid cancer is increasing • Overall good prognosis compared with

other cancers