What happens if thyroid cancer is left untreated?

Thyroid cancer: Potentially good prognosis on treated patients depending on type. If left untreated can grow locally or can spread to other places.

Growth: Not a good idea! the tumor will continue to grow and may spread to lymph nodes or metastasize through the blood stream. Left untreated long enough, it will eventually block the airway and cause choking sensations. Surgery is well tolerated - why would anyone not treat it?