Carcinoma of the thyroid gland usually presents as a midline neck mass. Clinically, palpable lymph node metastases are present in approximately 30% of the patients with papillary adenocarcinoma of the thyroid gland. In the absence of palpable neoplasm within the thyroid gland, the diagnosis of thyroid carcinoma from a biopsy of a regional neck mass is infrequent. We have recently experienced two cases of thyroid papillary adenocarcinoma that present as isolated cystic lateral neck masses with clinically normal thyroid glands. Occult thyroid cancer should be included in the differential diagnosis of unknown primary neck mas in adults.