Thyroid teratoma

Thyroid teratomas are rare tumors distinct from thyroid tissue found in mature teratomas, which are well documented ¹. Even rarer still are malignant teratomas of the thyroid.

Clinical presentation

The clinical presentation is generally no different than that of other thyroid masses, presenting with a palpable or visible lump in the anterior neck. If sufficiently large, it can also result in airway, neurovascular and/or esophageal compression. Depending on the types of tissue contained therein, hormonal secretion may also occur.

Some teratomas, particularly if malignant, can grow rapidly.

Pathology

Teratomas are a type of germ cell tumor that may contain a range of tissue that vary in maturity. Such tumors can contain varying types of immature or fully-formed tissue, such as hair, teeth, muscle or bone.

Thyroid teratomas are mostly benign, with very few case reports of malignant teratomas of the thyroid. Teratomas arise from pluripotent cells (either germ cell or embryonal cell lineage).

• germ cell: the teratoma will be located in the ovaries or testicles

• embryonal cell: usually located in the midline; skull, nose, tongue, neck, coccyx

Most teratomas are benign, but some can be malignant. The risk is dependent upon the age of the patient ^{1, 2}.

• teratomas are common in the pediatric population, where they are mostly benign

• whilst less common in adults, they are more likely to be malignant in adult patients

Treatment and prognosis

Due to the rare nature of the tumor, no established guidelines exist for treatment of thyroid teratoma. Useful investigations and treatment may include

• imaging: CT, ultrasound, MRI

  • further diagnostic imaging such as PET may be useful for staging if metastatic disease is suspected

  • thyroid teratomas can be graded with the ACR TI-RADS ³ reporting system.

• histological sampling: fine needle aspiration may be insufficient for diagnosis as the results are often indeterminate or unreliable ⁴

• serology testing: tumor markers, thyroid function

• surgical excision

  • followed by adjuvant chemotherapy and/or radiotherapy ⁴

History and etymology

The word teratoma is derived from Greek:

• 'téras' - monster

• 'oma' - tumor