Thyroid carcinomas found incidentally in the cervical lymph nodes: do they arise from heterotopic thyroid tissues?

Purpose: Thyroid carcinomas have been found incidentally in the cervical lymph nodes during surgery for head and neck squamous cell carcinoma (SCC). Such carcinomas have been considered a metastatic focus for malignant transformation of heterotopic thyroid tissue. We report on cases of so-called occult thyroid carcinoma in the cervical lymph nodes, and review the relevant literature.

Patients And Methods: We encountered 3 cases of incidental papillary carcinoma in the cervical lymph nodes of patients with oral SCC, and consequently reviewed 75 previously reported cases.

Results: Among 148 patients with oral SCC who had undergone cervical lymph node dissection, 3 were diagnosed with occult thyroid carcinoma. Papillary carcinomas were found in 3, 10, and 3 lymph nodes in cases 1, 2, and 3, respectively. Computed tomography showed 2 tumor-like shadows and 1 calcified mass in the thyroid gland in cases 2 and 3, respectively. These shadows did not enlarge during the 3 to 5 years of observation, and all patients are alive, without any events related to the neck and thyroid gland. Among the reviewed cases, approximately two fifths were histopathologically or clinically free from thyroid carcinoma. Progressive thyroid carcinoma was not detected in any patient.

Conclusions: We propose the possibility that thyroid carcinoma in the cervical lymph nodes is not necessarily metastatic, but may occasionally arise from heterotopic thyroid tissue.