[Folliculoid differentiation in medullary cancer of the thyroid gland]

Apart from production of argirophilic substance, tumor cells of medullary carcinomas of the thyroid gland form colloids due to differentiation of tumor elements into both argirophilic and colloid-producing cells. Accordingly, solid-follicular structures appear in them rather frequently. This requires the use of Grimelius test for differential diagnosis of medullar and follicular carcinoma of the thyroid gland.