Role of nuclear grooves in the diagnosis of papillary thyroid carcinoma. A quantitative assessment on fine needle aspiration smears.

Thirty-four cases of papillary thyroid carcinoma and 69 control cases consisting of 17 follicular neoplasms, 5 Hürthle cell neoplasms, 7 medullary carcinomas, 6 thyrotoxic goiters, 19 chronic lymphocytic thyroiditis cases, 3 subacute thyroiditis cases and 12 colloid goiter cases were studied for nuclear grooves. Such grooves were seen in 100% of papillary carcinoma and in 75-100% of other thyroid disorders, but their number was strikingly higher in papillary carcinoma. A quantitative assessment for nuclear grooves was made based on counting 500 follicular cells in hematoxylin and eosin (H&E)-stained and May-Grünwald-Giemsa (MGG)-stained smears. In H&E-stained smears of papillary carcinoma the number of cells with nuclear grooves (227.3 +/- 99.96 SD) was significantly higher as compared to other thyroid disorders (P < .01 to < .001). Eighty-eight percent of papillary carcinoma had nuclear grooves in > or = 20% tumor cells, whereas none of the other thyroid diseases exceeded this level. In MGG-stained smears the number of cells with nuclear grooves (40.7 +/- 32.83 SD) was also significantly higher as compared to other thyroid disorders (P < .05 to < .001). Of papillary carcinomas, 67.6% had > or = 4% cells with nuclear grooves, whereas 0-40% of other thyroid diseases exceeded this level. Nuclear grooves were significantly higher in H&E-stained smears of papillary carcinoma as compared to MGG-stained smears (P < .001). Based on this objective assessment, nuclear grooves were a useful criterion in the diagnosis of papillary thyroid carcinoma in H&E-stained smears but were not as reliable in MGG-stained smears.