Histology and fine-needle aspiration cytology of malignant thyroid neoplasms.

Malignant neoplasms of the thyroid are relatively infrequent tumors which present, like most pathological processes of this gland, as nodules. The commonest types are carcinomas, divided into papillary, follicular, medullary, insular and anaplastic carcinoma. Much less frequent are lymphomas and other non-epithelial malignancies. The fine-needle aspiration biopsy (F.N.A.B.) is the first choice method to investigate nodular thyroid lesions and to detect malignant tumors.