Lingual Thyroid

Fig: Arrows point to the ectopic thyroid tissue at the tongue base, above the epiglottis (arrowhead) on this sagittal-reformatted CT image.

Facts

• Thyroid tissue at the tongue base
  
• Most common location for ectopic thyroid
• Only site of active functioning thyroid tissue in 70% of cases
• Uncommon clinical problem but seen in approximately 10% of autopsy cases
• Become symptomatic at any age but usually during puberty, menses or pregnancy (increased metabolic demand)
• Malignant transformation very rare, incidence less than 1%. Suspected when a known patient with lingual thyroid develops new symptoms or clinical evidence of enlargement
  

CT Findings

• Characteristic location = in midline, at the tongue base (other types of ectopic thyroid can be anywhere from tongue base to anterior to the heart)
• Characteristic attenuation and enhancement = similar to thyroid tissue (very enhanced, may contain calcifications or low attenuation areas)
• Absent thyroid tissue in the expected normal location
  

Reference:
Kennedy TL, et al. Lingual thyroid carcinoma with nodal metastasis. Laryngoscope 2007 (November)