Thyroid cancer is the most common endocrine malignancy in the world. Generally, thyroid cancer could be divided into well-differentiated and poorly-differentiated. Well-differentiated thyroid cancers usually have two different patterns, including papillary thyroid cancer and follicular thyroid cancer. Thyroid sonography is convenient to obtain repeatedly for the images of nodular goiter. However, cytology and pathology are still the golden rules to make the final diagnosis. Under the basis of sono-guided fine needle aspiration cytology, diagnosis of papillary thyroid cancer is typically using fine needle aspiration cytology based on the presentation of typical cytologic features. On the other hand, thyroid follicular lesion cannot be interpretated via cytology because the evidence of capsular invasion or vascular permeation of capsule will not be available in fine needle aspiration cytology. Surgical intervention with pathological specimens is the only pathway to make the final diagnosis. Interestingly, both patterns of well-differentiated thyroid cancer shared the same follow-up tumor marker, i.e. serum thyroglobulin. Up to date, pre-operative diagnosis of follicular thyroid cancer is still one of the unresolved issues in endocrine oncology.