Fine Structure of Colloid Cells in the Thyroid Gland

Thin sections of colloid cells in the thyroid gland of the C3H mouse were observed with an electron microscope. There appeared to be 2 main kinds of colloid cells. In the first, the clear appearance of the cytoplasm is due to the presence of a very dilated cisterna of the granular reticulum in an otherwise normal appearing cell. In the second, the plasma membrane of the cell appeared disrupted and there was extensive replacement of the cytoplasm by material resembling colloid. No information is available yet on the origin of colloid cells but it is quite clear that they are not specific for thyroiditis or other recognized diseases of the thyroid gland