The potential value of the demonstration of thyroglobulin by immunoperoxidase techniques in fine needle aspiration cytology.

The peroxidase-antiperoxidase method for the demonstration of thyroglobulin was performed on 30 fine needle aspiration smears. All of the benign thyroid lesions plus the papillary and follicular carcinomas of the thyroid were positive for thyroglobulin. Two cases of metastatic thyroid carcinoma in lymph nodes were also positive. Medullary carcinoma of the thyroid and ten control smears from various other tissues were negative. This proves the sensitivity and the specificity of the method, which may be used in routine cytology and may add to the accuracy of diagnosing metastatic tumors suspected of being of thyroid origin. The intranuclear cytoplasmic vacuoles in papillary carcinoma of the thyroid were negative for thyroglobulin. This unexpected finding is demonstrated, and a possible explanation is offered.