Presentation and Diagnosis
ECT in children generally presents as an asymptomatic lateral neck mass.
Symptoms can occur as a result of infection,4, 18airway obstruction,5, 6, 34, 39 feeding
difficulties,46, 49 and rarely Homer
syndrome.50 We detected a significant higher incidence
of lesions located in the neck (79%) and in the male population (79%).
The lesion has also been described as an incidental finding in
paediatric autopsies with an incidence as high as to
31%.79 Rarely, ECT has been found in the autopsies of
children after sudden infant death syndrome although no clear
correlation has been identified with this.3 In a
review of autopsies with an incidental finding of cervical ectopic
tissue the ECT size demonstrated a negative correlation with age (r =
-0.75; p = 0.034) suggesting that the lesion may disappear over the
first few years of life.44
The differential diagnoses in children include; congenital or acquired
neck lumps such as dermoid and sebaceous cysts, thyroglossal duct cysts
and branchial remnants. USS is useful in the characterisation of ECT and
is now considered the first-line investigative
modality.71 Sonographically, thymic tissue is
identified by a homogeneous, hypoechoic mass with internal
echogenicities.10, 56, 71 However, despite the
presence of internal echoes in our case, the initial report suggested
the lesion to be a branchial cleft cyst. Overall, definite diagnosis,
leading to a conservative management was obtained in 30 (21%) patients.
For the 106 ECTs that were surgically excised, including our case, ECT
was not listed as a preoperative differential diagnosis. This suggests
that ECT is rarely considered in the differential diagnosis of neck
masses in children. Several authors have highlighted the challenges in
the pre-operative diagnosis of ECT mimicking other abnormalities such as
branchial cysts,18, 29, 31, 32, 37, 49lymphatic
malformations,18, 20, 29, 31, 77haemangiomas,29 hamartoma,37thyroglossal duct cysts,18, 77teratoma,46, 77 lymphoma,47, 59neuroblastoma,54 and dermoid
cysts.37
For clinically ambiguous cases, MRI has proven to be a superior
radiological modality to both characterize these lesions and document
any additional ectopic thymic tissue. It also confirms the presence of
continuity between the ECT and a mediastinal thymus, or the presence of
a normal mediastinal thymus.13 Thymic tissue is
identified by a homogeneous, isointense on T1 weighted images and
hyperintense on T2 weighted images.56 The signal
intensity is similar for ECT and orthotopic thymus.13
Diagnosis can also be helped by FNA or incisional biopsies. Tunkel et
al. documented that FNA can accurately diagnose ECT based on presence of
fibrous septa, Hassall’s corpuscles, and other characteristics of normal
thymic architecture.16 However, ECT has been
erroneously diagnosed on FNA as lipoblastoma,19branchial cysts33, 66 and lymph node
tissue/lymphoma.9, 33, 68 Incisional biopsy might also
be misleading and some authors have also highlighted the challenges
related to histological diagnosis with incisional biopsies reported as
infected/chronic inflammatory masses, vascular anomalies and
lymphomas.8, 15, 47 Similarly, in our patient the
incisional biopsy documented xanthogranulomatous inflammatory change and
fibrosis.