Tissue polypeptide antigen in thyroid tumours of follicular cell origin: an immunohistochemical re-evaluation for diagnostic purposes.

Using immunoperoxidase procedures on paraffin sections, we have investigated the distribution pattern of tissue polypeptide antigen (TPA) in follicular adenomas, (20 cases), follicular carcinomas (23 cases), papillary carcinomas (10 cases), anaplastic carcinomas (eight cases) and medullary carcinomas (four cases). Normal thyroid tissue surrounding adenomas was also tested as a control. Our results document positivity for TPA in follicular, papillary and medullary carcinomas, whereas no reactivity was encountered in follicular adenomas and anaplastic carcinomas. These immunohistochemical data were compared with serological levels of TPA and the findings were discordant only for anaplastic carcinomas. We contend that the demonstration of TPA, possible in alcohol- or formalin-fixed tissues, may prove to be of value in the differential diagnosis of thyroid adenomas from carcinomas of follicular cell origin.