Occult thyroid carcinoma: a rare case report and review of literature.

Occult thyroid carcinoma is very common in the clinic and is generally divided into four groups. Here, we proposed two types of occult thyroid carcinoma as the fifth group. The first type was locoregional lymph node metastases from thyroid carcinoma, and the second type was distant organ metastases from thyroid carcinoma. The unique aspect of the fifth group was that the primary carcinoma of the fifth group was not finally found by pathological examination. To better understand the fifth group, we reported a typical case. Furthermore, we discussed the diagnostic criteria and procedures and the management of the fifth group of occult thyroid carcinoma.