What is the difference between a thyroglossal duct cyst and a colloid cyst on exam?

Distinguishing Thyroglossal Duct Cyst from Colloid Cyst on Physical Examination

A thyroglossal duct cyst characteristically moves upward with tongue protrusion and swallowing, is located in the midline neck (typically near or below the hyoid bone), and presents as a painless mobile mass, whereas a colloid cyst (thyroid colloid nodule) does not move with tongue protrusion, moves only with swallowing, and is located within the thyroid gland laterally. 1, 2, 3

Key Physical Examination Maneuvers

Tongue Protrusion Test (Pathognomonic for TGDC)

• The thyroglossal duct cyst moves superiorly when the patient protrudes their tongue because the cyst is attached to the foramen cecum at the tongue base via the thyroglossal duct remnant 2, 3
• A colloid cyst within the thyroid gland does not move with tongue protrusion 1
• This single maneuver is the most discriminating physical finding between these two entities 3

Swallowing Assessment

• Both thyroglossal duct cysts and colloid cysts move with swallowing, as both are connected to structures that elevate during deglutition 2, 3
• This finding is not discriminatory between the two conditions 1

Location and Anatomic Distribution

Thyroglossal Duct Cyst Location

• Midline position anywhere from the foramen cecum to the thyroid isthmus 1, 2, 4
• Most commonly located just below the hyoid bone (approximately 65% of cases) 2, 3
• Can rarely extend to the suprasternal notch 4
• Always in or very near the midline 1, 3

Colloid Cyst (Thyroid Nodule) Location

• Located within the thyroid gland itself, typically lateral to midline 1
• May be palpable in the right or left thyroid lobe 1
• Not truly midline unless arising from the isthmus 1

Palpation Characteristics

Thyroglossal Duct Cyst

• Smooth, mobile, non-tender mass (unless infected) 2, 5, 3
• Typically 1-5 cm in diameter (mean 2.5 cm), though giant cysts up to 12 cm have been reported 2, 4
• Cystic consistency on palpation 2, 6
• When infected, becomes painful, tender, and may have overlying erythema 5

Colloid Cyst/Nodule

• Firm to rubbery consistency 1
• May be part of a multinodular goiter with multiple palpable nodules 1
• Generally non-tender unless hemorrhage has occurred 1

Age and Presentation Patterns

Thyroglossal Duct Cyst

• Most commonly presents in children under age 10 (63.8% of cases) 3
• Can present in adults, though less common; when it does, infection is the most common presentation 5
• Congenital lesion that becomes symptomatic over time 2, 5

Colloid Cyst

• More common in adults, particularly middle-aged and older individuals 1
• Part of the spectrum of benign thyroid nodular disease 1

Critical Clinical Pitfalls

Common Diagnostic Errors

• Failing to perform the tongue protrusion test, which is the single most important discriminating maneuver 2, 3
• Assuming all midline neck masses are thyroglossal duct cysts without considering thyroid isthmus lesions, dermoid cysts, or lymphadenopathy 1, 2
• In infected thyroglossal duct cysts, the inflammatory changes may obscure the classic physical findings 5

When Physical Exam is Insufficient

• If the mass is very lateral, consider it is not a thyroglossal duct cyst 1, 3
• Ultrasound should be obtained when physical examination findings are equivocal 7, 6
• CT with contrast may be needed if there is concern for malignancy or invasion 1, 7

Algorithmic Approach to Examination

1. Identify location: Is it midline or lateral? (Midline suggests TGDC; lateral suggests thyroid nodule) 1, 3
2. Perform tongue protrusion test: Does it move up with tongue out? (Yes = TGDC; No = likely thyroid nodule) 2, 3
3. Assess swallowing: Does it move with swallowing? (Both will move, so not discriminatory) 2, 3
4. Palpate consistency: Cystic and smooth (TGDC) vs. firm/rubbery (colloid nodule) 2, 6
5. Check for infection signs: Tenderness, erythema, pain with swallowing (suggests infected TGDC) 5