Thyroglobulin in human thyroid follicles with acid mucin.

The minority of human thyroid follicles that contain acid mucin are often grouped in the C-cell area of the gland, and are lined by abundant C cells. They are thought to be derived from the ultimobranchial contribution to the thyroid gland. This study demonstrates the presence of thyroglobulin reactive follicular cells and colloid as well as calcitonin and CGRP in these ultimobranchial-related thyroid follicles. These findings add further support to the belief that the ultimobranchial body is a source of at least some C cells and follicular cells, and support the view that thyroid mixed medullary follicular neoplasia may originate from an ultimobranchial stem cell line.