☻Medullary ca is non differentiated thyroid ca which arise from C-cells. ☻risk factor: Hereditary condition called multiple endocrine neoplasia, or MEN, type 2A and 2B. In these conditions, one or more of the endocrine glands like the thyroid gland, parathyroid gland, and adrenal gland develop tumors. ☻sporadic: solitary growth ☻familial: multicentric growth ☻Spread locally, lymphatic & haematological. ☻aggrasive growth