Prevalence of Ectopic Intrathyroidal Thymus in Japan: The Fukushima Health Management Survey

Abstract

The results reflect the prevalence of ectopic intrathyroidal thymus using ultrasonography in the general population. Further examination will be needed by way of longitudinal follow-up.

Ectopic Intrathyroidal Thymic Tissue Mimicking Thyroid Nodules in Children

“…There was no association between the presence of an intrathyroidal thymus and other abnormalities at autopsy, and the authors hypothesized that it may be a common variant of normal anatomy. This hypothesis was supported by the publication of ultrasound screening data from the Fukushima Health Management Survey . In this large prospective study, baseline sonograms of 37,816 children who lived in Fukushima Prefecture at the time of the Daiichi nuclear incident showed ectopic intrathyroidal thymic tissue in 375 (1%) of the participants.…”

“…Of note, because the prevalence of true thyroid nodules increases with age, and normal thymic tissue (and presumably an intrathyroidal thymus) spontaneously involutes in later childhood, there is limited overlap between an intrathyroidal thymus and thyroid malignancy. In particular, the very high prevalence (1.7%) of a sonographically detected intrathyroidal thymus reported in the youngest group (0–4 years) studied in the Fukushima Health Management Survey corresponds to an age when thyroid neoplasia is exceedingly rare.…”

Prevalence and sonographic features of ectopic thyroidal thymus in children: A retrospective analysis

“…These cervical components may mimic extrathyroidal ectopic thymus, but their continuity with the mediastinal thymus helps in distinguishing between the two entities. During embryogenesis, migration arrest can lead to the development of ectopic thymus along the pathway of descent . Most ectopic thymic arrests are thyroidal in location and are detected incidentally while the patient is being investigated for other reasons.…”

“…Their unique appearance on sonography (US) helps the radiologist in identifying them . Although ectopic thyroidal thymus is thought to be rare, a limited number of studies have investigated the prevalence of ectopic thyroidal thymus in the general population . In this retrospective study, we aimed to assess the prevalence of ectopic thyroidal thymus detected by US in children and analyze the gray scale and color Doppler US features that are useful to differentiate this anatomic variant from other neck and thyroid lesions.…”

Concurrent intrathyroidal thymus and parathyroid in a patient with papillary thyroid carcinoma: a challenging diagnosis

“…Intrathyroidal thymus is considered to be a rare entity; however in the work by Fukushima et al . (3), prevalence was found to be about 1% in Japanese children.…”