Optically clear nuclei in papillary carcinoma of the thyroid: Demonstration of one of the fixation artifacts and its practical usefulness

To examine whether or not optically clear nuclei are one of the fixation ar tifacts in papillary carcinoma of the thyroid. Experiments using an optimal immersion fixation method by making thin-sliced specimens, 5 x 2 x 2 mm in size were adopted. Fixatives tested were 10% formalin, 10% buffered formal in, mixture of alcohol and formalin (4 : 1), 95% alcohol, 4% phosphate-buff ered paraformaldehyde, Carnoy's fixative, Bouin's fixative and various conc entrations of formalin, Tested thyroid lesions in total were: cases with pa pillary carcinoma (38); follicular carcinoma (one) follicular adenoma (15); adenomatous goiter (11); Hashimoto's thyroiditis (two); Grave's disease (f ive); and normal thyroid tissue around tumor (five), Routinely processed pa pillary carcinoma showed a high occurrence (64.6%) of the optically clear n uclei contrasted by a low occurrence (almost 0%) in other lesions. However, this rate in papillary carcinoma decreased (< 35.3%) in all experimental g roups irrespective of the choice of fixatives, Frequent occurrence (61.9-66 .6%) of the optically clear nuclei was reproduced in papillary carcinoma fi xed in a higher concentration of formalin (40-60%) in the experimental grou ps. These results demonstrated that the optically clear nuclei are one of t he fixation artifacts, although still useful as a diagnostic criterion.