What are symptoms of thyroid cancer?

Variable. Early cancer may be asymptomatic. Common symptoms include, mass in the neck over the trachea, lateral mass due to metastases in the lymph nodes of the neck. Metastases to other organs, e.g., lung and bone may be the first symptoms. If the cancer produces hormone, anxiety, nervousness, high pulse rate, heat intolerance, weight loss etc due to hyperthyroid state may be the presenting feature.
A painless lump. Most people with thyroid cancer do not have symptoms - they have a painless lump in the thyroid (we call it a nodule). Sometimes (especially younger patients) can have a palpable lymph node as the first sign. Rarely, very aggressive cancers can become large and cause symptoms of breathing obstruction.