Figure 4c. Thyroid carcinoma in a 45-year-old woman with a history of breast cancer who was referred for posttherapy evaluation. Axial PET scan (b) reveals a hypermetabolic focus in a cervical lymph node in the left side of the neck (arrowhead) that is highly suspicious for metastatic disease. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the focus (arrowhead) corresponds to the left thyroid lobe and is consistent with a thyroid nodule. Subsequent ultrasonography demonstrated a multinodular gland with a dominant nodule in the left lower pole. Further investigation with needle biopsy revealed follicular carcinoma of the thyroid gland. PET-CT findings confirmed that the patient had thyroid disease (adenoma or carcinoma) rather than lymph node metastasis; however, the nodule could not be characterized on the basis of PET-CT findings alone.