Undescended thymus presenting as midline neck swelling.

Area of Science:

• Pediatric Surgery
• Endocrinology
• Anatomy

Background:

• Ectopic thymus, a rare congenital anomaly, can present as a neck mass.
• Undescended thymus is often asymptomatic but can cause localized symptoms.
• Solid-type ectopic thymus is less common than the cystic variant.

Observation:

• A seven-month-old male infant presented with a midline neck swelling.
• The swelling, located in the suprasternal notch, was prominent during crying.
• Computed tomography confirmed the mass to be solid thymic tissue.
• No thymic tissue was identified in the normal thoracic location.

Findings:

• The patient had an undescended or ectopic thymus.
• The ectopic thymus was solid in type, accounting for 10% of such cases.
• Cystic variants constitute the remaining 90% of ectopic thymic tissue.

Implications:

• Ectopic thymus is a rare differential diagnosis for pediatric neck masses.
• Surgical excision requires caution, as the ectopic thymus may be the sole source of thymic function.
• This case highlights the importance of pre-operative imaging and careful surgical planning.