Intrathyroidal ectopic thymus in children

Abstract

As ultrasound is commonly used these days, more and more lesions are found incidentally, including simple cysts, isoechoic nodules, and hypoechoic nodules, such as ectopic thymus. We here report the prevalence of ectopic thymus and its natural course.We retrospectively reviewed the charts of 690 subjects (342 males, 348 females) who were under 18 years old and had undergone neck or thyroid ultrasound at Hallym University Sacred Heart Hospital from January 2014 to June 2017. Ectopic thymus was defined when the incidental lesion was hypo- to iso-echoic compared to adjacent muscles with vascularity and did not have a connection to the thymus in the mediastinum.Of the 690 children, 16 (9 males, 7 females; median and ranges of age at diagnosis, 13 months and 18 days to 10 years) were diagnosed as having ectopic thymus. The most common location of ectopic thymus was in the inferior aspect of the left thyroid lobe. The median and ranges of the longest diameter at the time of initial diagnosis was 22.5 mm and 8 mm to 38 mm, respectively. Four cases underwent follow-up ultrasound, of which 3 cases showed no change in size and 1 case showed decreased size.Ectopic thymus should be kept in mind when a lesion is found in the neck and thyroid incidentally, and physicians should reassure parents about its benign course.

Ectopic cervical thymus in children: Clinical and radiographic features

“…Our study found that 73% of lesions occurred in the central neck. Recent studies have found most ECT lesions to occur in the central neck, and are either intrathyroidal (Type C1 or C2) or extrathyroidal (Type B) . These lesions may create a diagnostic dilemma for providers concerned about the possibility of thyroid malignancy.…”

Pharyngeal Ectopic Thymus: A Case Report

“…4 Many studies have reported that the location of ectopic thymus was adjacent to the thyroid gland. 6 However, the 2 units are not presumed as one organ due to their differences in functions.…”

Fusiform Cervical Mass in a 6-Year Old Boy; Do not Forget the Thymic Cyst

“…Thymic cysts may be congenital; in such a case, they can be practically found anywhere along the thymo-pharyngeal duct (9). In their retrospective analysis, Bang et al demonstrated that only 1 out of 16 cases examined in total corresponded to ectopic thymus located at the supraclavicular area (10). Rarely, thymic remnants are detected in atypical sites, such as the retropharynx (16).…”

“…Cervical thymic cyst represents a rare entity, with only about one hundred cases reported in the literature so far (9). According to findings from patients who underwent neck or thyroid ultrasonography, the prevalence of ectopic thymus varies widely from 2.3 to 17.3% (10,11,12). Kim et al examined 3,195 patients, demonstrating a prevalence equal to 0.4% (13).…”

“…Despite the fact that the majority of ectopic thymic lesions are located in proximity with the thyroid gland, many pediatricians are not familiar with these entities (10). Through this case study, we aim at highlighting some certain features of thymic cysts, along with a comprehensive research of the relevant literature.…”