The value of immunohistochemistry in medullary thyroid carcinoma: a systematic study of 30 cases.

Thirty cases of medullary thyroid carcinoma were investigated by immunoperoxidase staining techniques to evaluate the diagnostic significance of neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), somatostatin (SOM), a-subunit of human chorionic gonadotrophin (a-hCG), serotonin (5-HT) and adrenocorticotropic hormone (ACTH) immunoreactivity as diagnostic markers in comparison to different calcitonin (CT) staining patterns. Twenty three cases exhibited a strong (group I) or moderate (group II) staining intensity for CT and did not need further immunocytochemical proof for classifying them as medullary carcinoma. From seven cases which showed only a weak or borderline CT-immunoreactivity (group III), six stained positively for NSE and four positively for CEA. SOM-positive cells were identified in six cases and a-hCG or 5-HT-positive cells respectively in three cases of group III. Twenty follicular and 20 papillary carcinomas also included in this study did not react with any of the above mentioned antibodies. Therefore, NSE and CEA represent useful additional diagnostic markers particularly for the identification of medullary carcinoma with weak or borderline CT-immunoreactivity. The identification of other peptides may also be helpful in demarcating it from thyroid tumours of follicular cell origin.