Immunostaining of Papillary Carcinoma 
of the Thyroid

Immunostaining of tumour sections with antithyroglobulin antibody is helpful in confirming the follicular cell origin of the differentiated carcinomas, particularly in metastases of undetermined origin. Obtaining a positive reaction with anticalcitonin is now an essential step in the histological diagnosis of medullary carcinomas (Fig. 16.15). The majority of these tumours also give a positive immunoreaction with anticarcinoembryonic antigen. 
Other immunoreactive peptides that are occasionally demonstrable include somatostatin, gastrin-releasing peptide (or its fragment, known as bombesin), adrenocorticotrophic hormone (ACTH), and corticotrophin-releasing hormone.