Discussion
Lingual thyroid represents 90% of all cases of ectopic
thyroid2,4. Hickmann recorded the first case of
lingual thyroid in 18695. It is a rare embryogenic
anomaly and results from failure of descend of thyroid from foramen
caecum to its normal entopic prelaryngeal location6.
The prevalence rate varies from 1:100,000 to 1:300,000(3). Female to
male ratio ranges from 3:1 to 7:17. Lingual thyroid
may be asymptomatic, incidentally discovered during clinical
examination. It may present as a sooth lobulated mass in throat. The
mass can cause obstruction of oropharynx and cause dysphagia, foreign
body sensation in throat, dyspnoea, stridor, snoring
etc8. Other symptoms might result from thyroid
insufficiency. Features of hypothyroidism like weight gain, tiredness,
menstrual irregularity, loss of appetite maybe present. Very rarely,
lingual thyroid can undergo malignant transformation. Malignancy in
entopic thyroid gland is mostly papillary carcinoma. Contrary to it,
malignancy in ectopic thyroid gland is mostly follicular
carcinoma2. The malignant mass presents as an
ulcerative, rapidly growing mass in throat. Imaging is the modality of
choice for diagnosis. Ultrasonography is the most convenient and easy
one. It has no radiation. The most consistent finding is absence of
thyroid gland in its entopic location. Thyroid tissue may be found along
the path of descend of thyroid gland. Sometimes the gland maybe
hypoplastic and not visualized in ultrasound9. CT is
another modality but often avoided due to radiation. In non-contrast CT,
thyroid gland is hyperdense and show homogeneous post contrast
enhancement10. Lingual thyroid is seen at base of
tongue, between sulcus terminalis and epiglottis. In MRI, lingual
thyroid is seen as a non-invasive mass in base of tongue. Thyroid tissue
is iso to hyperintense in T1 weighted image. In T2 weighted image,
thyroid can be hypo to iso to hyperintense. In post contrast images,
homogeneous enhancement is seen6. Scintigraphy with
Tc-99m is another reliable diagnostic tool. Absence of isotope uptake in
cervical region and presence of uptake in oropharynx points towards
diagnosis of lingual thyroid11.
Outcome : The patient was given levothyroxine suppression
therapy. Patient was followed after 1 month. The mass was markedly
reduced in size. The patient was euthyroid. Maintenance done of
levothyroxine was given and regular follow up was done. Other
therapeutic options can be surgical removal and radioactive iodine
ablation11. Surgery is reserved for patients with
severe symptoms refractory to medicines. Radioactive iodine is avoided
in children and young adults11.