Papillary Thyroid Carcinoma: Ectopic Malignancy versus Metastatic Disease

Area of Science:

• Endocrinology
• Oncology
• Pathology

Background:

• Papillary thyroid carcinoma (PTC) commonly metastasizes to regional lymph nodes.
• Ectopic thyroid tissue, rare in the lateral neck, can be the only functional thyroid.
• Malignant transformation of ectopic thyroid tissue is uncommon, with PTC even rarer.

Observation:

• A 33-year-old man presented with a lateral neck mass discovered after a motor vehicle accident.
• Investigations revealed papillary thyroid carcinoma in ectopic thyroid tissue within the lateral neck.
• The patient's native thyroid gland showed no evidence of malignancy.

Findings:

• The final diagnosis was malignant transformation of heterotopic thyroid tissue.
• This case is unique as the ectopic tissue harbored PTC, while the orthotopic thyroid was cancer-free.
• Cervical lymph node metastasis was the sole presentation of occult papillary thyroid carcinoma.

Implications:

• Ectopic thyroid cancer should be considered in the differential diagnosis of neck masses.
• Management requires individualized risk assessment, potentially including total thyroidectomy, neck dissection, and radioiodine therapy.
• This case underscores the importance of thorough evaluation for ectopic thyroid tissue in unexplained neck masses.