Prevalence of cervical extension of the thymus in children

The cervical extension of the thymus is the most common variation. However, this may be mistaken for a soft tissue mass in the neck particularly by the radiologists who are not familiar with the pediatric population and not aware of this variation, leading to unnecessary surgery and increased medical costs. Since the rates of cervicaly extended thymus in children in clinical practice are lacking in Turkey, this study aimed to evaluate the prevalence of cervical extension of the normal thymus in the pediatric population.

This descriptive cross-sectional study included all pediatric patients who were referred to the radiology department for neck ultrasonography between August-October 2018. A high-frequency probe was implemented and 220 patients (152 male, 68 female) with a mean age of 8.7 ± 4.39 years (ranging from 1 month to 18 years of age) were examined.

Cervical extension of the thymus was detected in 103 patients (46.8%). The age of the patients was found to be significantly lower than the age of the patients whose thymus was not extended (7.87 ± 4.15 years and 9.59 ± 4.46 years, respectively. p = 0.006). The mean craniocaudal length of the thymus that cervically extended was 6.41 ± 2.31 mm. There was no significant difference in the length of the thymus between males, females (6.48 ± 2.12 mm and 6.37 ± 2.46 mm. p = 0.924), and different age groups (p = 0.442).

Approximately half of the children have the cervical extension of the thymus. Thus, radiologists and clinicians should be aware of this entity to avoid unnecessary imaging studies and interventional procedures.