<prompt> Most well differentiated thyroid tumor isPapillary carcinomaMedullary carcinomaFollicular carcinomaAnaplastic carcinoma  <response>: A Papillary carcinoma Follicular cell origin: A Differentiated. B Undifferentiated. DIFFERENTIATED: Papillary carcinoma 60; Follicular carcinoma 15; Mixed papillary and follicular carcinoma. UNDIFFERENTIATED: Anaplastic carcinoma 13. Clinical features: It is the most slow growing among the malignant tumours of the thyroid. 