Thyroglobulin

Thyroglobulin is a large glycosylated protein. Thyroxine (T3 and T4) synthesis occurs at specific tyrosine residues on thyroglobulin.

Immunohistochemical expression

thyroid follicular epithelium and colloid
all follicular neoplasms of the thyroid
all papillary carcinomas of the thyroid
Hurtle cell tumours of the thyroid
up to 50% of poorly differentiated and anaplastic carcinomas of the thyroid
some medullary carcinomas of the thyroid: see calcitonin

Antibodies to thyroglobulin do not react with epithelial cells of the lung, breast, gastrointestinal tract, pancreas, kidney or with the carcinomas of these organs. A case of moderate immunoreactivity in one ovarian serous papillary carcinoma from a series of seventeen has been reported¹.

Diagnostic utility

Identification of primary and metastatic carcinomas of the thyroid. If staining occurs selectively at the periphery of a tumour within the thyroid, it is probably artefactual due to diffusion of thyroglobulin from the surrounding thyroid.
In combination with calcitonin, to identify medullary carcinomas of the thyroid.
In combination with thyroid transcription factor-1, to differentiated between primary thyroid and lung neoplasms. Those well differentiated thyroid neoplasms which are likely to be TTF-1 positive are also likely to be positive for thyroglobulin. Rarely, anaplastic carcinoma of the thyroid may be positive for TTF-1 but negative for thyroglobulin².

References

¹Keen, C. E., Szakacs, S., Okon, E., Rubin, J. S., Bryant, B. M. CA125 and thyroglobulin staining in papillary carcinomas of thyroid and ovarian origin is not completely specific for site of origin Histopathology 1999;34:113-117

²Bejarano, P. A., Y. E. Nikiforov, et al. (2000). "Thyroid transcription factor-1, thyroglobulin, cytokeratin 7, and cytokeratin 20 in thyroid neoplasms." Appl Immunohistochem Mol Morphol 8(3): 189-94.

This page last revised 8.11.2003.