A biopsy from a mass in front of the neck revealed parafollicular cells. How do you follow up?

Biopsy from the mass in front of the neck revealed parafollicular cells indicating that it's a case of Medullary carcinoma of the thyroid. Medullary carcinoma of the thyroid (MTC): It is a distinct thyroid carcinoma that originates in the parafollicular C cells of the thyroid gland. These C cells produce calcitonin. Hence it is used for follow up of these patients