Nuclear grooves in the aspiration cytology of papillary carcinoma of the thyroid.

Nuclear grooving has recently been shown to be a useful morphologic feature in the diagnosis of papillary carcinoma of the thyroid in tissue sections and imprint smears. In order to assess the diagnostic value of nuclear grooving in cytologic specimens, the presence of this feature was evaluated in fine needle aspirates from 20 papillary carcinomas of the thyroid, 10 follicular adenomas, 3 follicular carcinomas, 1 medullary carcinoma, 10 nodular goiters and 4 cases of Hashimoto's thyroiditis. In each case, 30 random high-power fields (HPFs), or all fields in less cellular smears, were examined, and the percentage of the fields in which nuclear grooving could be seen was recorded. Seventeen of 20 papillary carcinomas (85%) showed nuclear grooves in more than 25% of the HPFs examined; in the remaining three cases, grooves were observed in less than 25% of the HPFs. In control cases (all other thyroid lesions), nuclear grooves either were absent or were present in less than 25% of the HPFs examined. These findings suggest that nuclear grooving, when seen in abundance, can be considered a reliable criterion for the diagnosis of papillary carcinoma in fine needle aspiration cytology of the thyroid. The presence of occasional grooves, however, should be regarded as a nonspecific finding.