Patients With a Single, Small (2 cm or Less) Cancer Nodule in the Thyroid Gland Will be Offered Active Surveillance Initially for 5 Years. In Case of Cancer Growth or Changes in Ultrasonographic Appearance, Further Treatment Will be Offered.

Inclusion criteria: * age of 30 years or older AND * single, well-defined tumor in the thyroid gland, with a FNAB suspicious of cancer or diagnostic of cancer (category V or VI in the Bethesda system) AND * tumor size of 2 cm or less in all dimensions. Exclusion criteria: * suspicion of disseminated disease because of: * PET-positive lymph nodes on the neck * suspicious lymph-nodes by neck ultrasonography (US) * signs of capsular invasion of the tumor * suspicion of metastatic disease due to findings on PET-CT-scan or thoracic CT-scan; OR * tumor placement at a high-risk location (in the thyroid capsule or near the trachea) OR * previous thyroid surgery OR * concomitant hyperparathyroidism (ionized calcium \> 1.32 mmol/L and PTH \> 6 pmol/L) OR * if the patient is pregnant OR * If the patient is unable to give informed consent.