Neobook — clinical reference

Introduction
Causes of Thyroid Enlargement/Thyroid Function and Clues to the Aetiology
Differential Diagnosis of Thyromegaly Seen in a SA Thyroid Clinic
Thyromegaly Algorithm
Features To Look For in Ultrasound Evaluation of Thyroid Nodules
Bethesda Cytological Reporting of Thyroid Nodules

Context: Outpatients

Introduction

Most masses in the lower 1/3 of the neck, located between the sternocleidomastoid muscles, and below the level of the thyroid cartilage are thyroid enlargements. Ask the patient to swallow - if the mass moves visibly, it confirms that it is of thyroid origin. It is important however to remember that (rarely) other pathology may also occupy this anatomical space.

Conditions	Features
Thyroid Enlargement	Accounts for 95% - central or on either side of the trachea, moves on swallowing
Thyroglossal Cyst	Superior to tracheal cartilage, just on either side of the midline, moves on protrusion of the tongue (embryological attachment to foramen caecum of the tongue)
Pre-tracheal Lymph Nodes	Typically metastatic thyroid carcinoma nodes (Delphian nodes)
Plunging Ranula (Salivary Gland Cyst)	This is a floor of mouth condition- bimanually palpable, transilluminates. Mostly seen in ENT

Ask about symptoms suggestive of thyroid dysfunction (hypo- and hyperthyroidsim), symptoms of local compression, and family history of thyroid and other endocrine illnesses.

On clinical examination, it is simple to decide if the mass you see and feel is thyroid in origin. A normal-sized thyroid is not palpable nor is it visible, even in very thin individuals - thus the presence of a thyroid mass equates with enlargement, usually caused by a pathological process. A subtle thyroid enlargement is better SEEN than palpated: always ask the patient to swallow and inspect the neck from 2-3 meters (the usual distance if you are consulting across a desk). Consider if the thyroid is symmetrically enlarged (i.e. can you feel both lobes = goitre) or if the abnormality is a one-sided enlargement (solitary nodule). Evaluate if there is associated lymphadenopathy, airway deviation and retrosternal extension of the mass. Look for clinical signs of thyrotoxicosis and hypothyroidism.

Because the clinical evaluation of thyroid form and function is subjective, it is routine to order a neck US and blood tests to evaluate thyroid function.

Causes of thyroid enlargement/ thyroid function and clues to the aetiology

Abnormalities of Form (Shape)	Abnormalities of Function
		Hypothyroid	Euthyroid	Hyperthyroid
	Smooth Goitre	Thyroiditis	Physiological goitre	Grave's disease Thyroiditis
	Nodular Goitre	Hashimoto's thyroiditis MNG	MNG	Toxic MNG
	Single Nodule / Unilateral	Uncommon scenario	Hyperplastic nodule Cyst Adenoma Carcinoma	Toxic Adenoma

Differential diagnosis of thyromegaly seen in a SA thyroid clinic

Incidence	Clues
MNG (70%)	Can be massive in size, usually bilateral lobes involved Most commonly euthyroid, but over time drifts towards hypothyroidism
Hyperplastic Nodule (20%)	The commonest cause of single thyroid nodule
Graves/Hashimoto's Thyroiditis (5%)	Present with thyrotoxicosis or hypothyroidism Thyroid enlargement moderate in volume
Carcinoma (5%)	Typically presents with single thyroid nodule Suspect if lymphadenopathy, voice changes, recent increase in size

Thyromegaly algorithm

Think	Do	Plan
What is the thyroid shape and size? Is there airway compression? Is the patient thyrotoxic or euthyroid? What is the aetiology? Could this be cancer?	US examination FNA cytology (of single nodule or suspicious nodule within an MNG, do not bx if <1cm) TFT's Thyroid antibodies in cases of suspected thyroiditis	Review with a surgical colleague

Features to look for in ultrasound evaluation of thyroid nodules

Calcifications

Microcalcifications : Punctate echogenic foci without posterior shadowing; most specific finding associated with malignancy (~95%)

Coarse calcifications : Can be seen in both benign and malignant nodule

Peripheral rim calcification : Seen in both benign and malignant nodules

Echogenicity

Hypoechoic solid nodule : Nearly all medullary thyroid carcinomas; benign nodules can be hypoechoic

Isoechoic solid nodule : 25% (follicular and medullary)

Hyperechoic solid nodule : 5% chance of being malignant; large cystic component; favours a benign entity

Colour doppler

Intranodular flow : Usually malignant

Lymph nodes with increased colour Doppler flow are suspicous

Other

Invasion of local structures : Favours anaplastic thyroid carcinoma and thyroid lymphoma

Shadowing around the edges of a nodule : Associated with papillary thyroid carcinoma

A nodule is taller than it is wide : Is suspicious for malignancy

Irregular margins : Are suspicious for malignancy

Lymph nodes

Enlarged regional lymph nodes are suspicious for thyroid malignancy, esp. papillary thyroid carcinoma

Microcalcifications in regional lymph nodes are highly suspicious

Lymph nodes with cystic change are highly suspicious

Loss of normal fatty hilum, irregular node appearance

Increased colour Doppler flow is suspicious

Features of a Benign Nodule	Features of a Malignant Nodule
Large cystic component Hyperechoic solid Comet tail artefact Small	Hyperechoic solid Presence of microcalcifications Local invasion of surrounding structures Taller than it is wide Large size >2.5cm Suspicious neck lymph nodes suggesting metastatic disease Intranodular blood flow

Bethesda Cytological Reporting of Thyroid Nodules

	Finding	Risk of Malignancy	Treatment Decision
1	Inadequate	n/a	Repeat biopsy
2	Benign	0-3%	Reassure
3	Atypia, indeterminate	5-15%	Repeat biopsy in 6 months
4	Follicular neoplasm or suspicious	15-30%	Lobectomy
5	Suspicious for malignancy	60-75%	Lobectomy or total thyroidectomy
6	Malignant	97-99%	Lobectomy or total thyroidectomy