In present times, increasing use is being made of fine-needle aspiration biopsy of thyroid nodules. Although cytopathologists can identify papillary (Fig. 16.17), anaplastic, and medullary carcinomas and lymphomas, it is not possible to differentiate between follicular adenomas and follicular carcinomas using cytological smears since the latter tumours require identification of vascular invasion for diagnosis. Additionally, it may be difficult to differentiate between colloid nodules and colloid-rich adenomas. Although false positives and false negatives have been reported to have occurred in a minority of cases, the procedure has proved to be extremely helpful (essential even) in the examination of a solitary nodule. A clear-cut positive diagnosis of the carcinoma obviates the need for radioactive imaging.
