[Thyroid cytology: evaluation and perspectives]

For the majority of centres worldwide that specialize in the treatment of thyroid diseases, cytology is now the first investigation carried out in patients with thyroid nodules. Procedures and expected results of this examination are described, together with the progress accomplished by immunocytochemical detection of malignancy markers such as thyroid peroxidase (TPO). Puncture biopsy is preferably by fine needle aspiration, the quality of the examination depending essentially on the quality of the specimen and the cytologist's experience. Results are recorded as benign (colloid nodules and thyroiditis), intermediate (microfollicular tumors, doubtful lesions) and malignant (follicular, papillary, anaplastic and medullary carcinomas). In experienced hands, the average sensitivity of the examination for cancer detection is 90 to 95% and its specificity 65 to 75%. These limits result from a non significant level of sampling of 10 to 20% and the persistence of 2 to 5% of false negatives, independent of the cytologist's expertise. Based on results of an ongoing cohort study comprising at present 300 histologically controlled cases, immunodetection of TPO in puncture biopsy specimens using MAb 47 antibodies could result in a sensitivity of about 100% for a specificity of more than 90%.