BACKGROUND
The thymus originates around 6 weeks of gestation from the paired third
pharyngeal pouches together with the inferior parathyroid
glands.1 Fusion of the bilateral primordial thymus
occurs around the 8th week of gestation. The thymus
then migrates caudally along the line of embryological descent to enter
into the anterior mediastinum. Ectopic cervical thymus (ECT) is a rare
lesion caused by the abnormal descent of the thymus gland into the
mediastinum and represents less than 1% of neck lesions in
children.2 The lesion can be solid, partially or
predominantly cystic, with the latter accounting for majority (76-92%)
of cases.3 The presentation is generally with an
asymptomatic lateral neck lump. Symptoms can occur as a result of
infection, airway obstruction or, in neonates and infants, feeding
difficulties in large ECT.4-9 The diagnosis can be
suspected with ultrasound scan (USS).10-12 However,
magnetic resonance imaging (MRI) has the added benefits of clarifying
the anatomy, especially the relation with neck vascular structures,
documenting additional ectopic thymic tissue in the neck and the
presence of a normal mediastinal thymus.13 Fine needle
aspiration cytology (FNAC) may also be helpful in the diagnosis although
might not always be accurate.14-16 Surgical excision
might be indicated in large symptomatic masses. Nevertheless, in
children, conservative management might be appropriate in asymptomatic
cases and in the absence of a normal mediastinal thymus; this is to
prevent rendering a child athymic and subsequently
immuno-incompetent.9, 17, 18 We herein describe a case
report of a 10-year old girl with a right neck ECT which was initially
misdiagnosed as branchial cyst. We also performed a systematic review of
the paediatric literature in the last 20 years. We aim to clarify the
management of ECT in children.