Cytologic grading of aggressive and nonaggressive variants of papillary thyroid carcinoma.

To distinguish preoperatively between the usual nonaggressive (classic, follicular, and mixed-papillary and follicular variants) and the aggressive (tall-cell, columnar-cell, and sclerosing diffuse) variants of papillary thyroid carcinoma (PTC), the fine-needle aspiration cytologic smears of 30 cases of PTC were retrospectively reviewed. A three-class grading system, based on the evaluation of four cytologic parameters (cell size, number of nuclear pseudoinclusions, nuclear pleomorphism, and type of chromatin), was applied to each case. A statistically significant association between the cytologic classes and the histologic features of the cases was found. All cytologic grade 1 cases corresponded to the nonaggressive histologic variants, whereas all cytologic grade 3 cases showed features of the aggressive variants of PTC at histologic level.