The appearance of a solitary lateral cervical cystic mass as the only initial presenting symptom of occult thyroid carcinoma is uncommon. Its presence is often misdiagnosed due to the more frequent branchial cyst in young people. Although oronasopharyngeal squamous cell carcinoma has been reported as the main cause of lymph neck node metastasis, thyroid papillary carcinoma may be responsible for solitary cervical cystic masses as the initial manifestation of the disease. This situation has been rarely reported, although solid masses are much more frequent. In most of these cases all such lesions may initially be considered as metastatic foci from a primary thyroid lesion. However, an alternative explanation by means of which ectopic thyroid tissue is associated with a branchial cyst has to be considered, especially if no primary tumour is observed in the histological examination of the thyroid gland. We present a rare case of solitary cystic lymph node metastasis of occult papillary carcinoma of the thyroid. We also discuss possible etiology for thyroid papillary carcinoma in lateral neck cysts.