Clear nuclei of papillary thyroid carcinoma conspicuous in fine-needle aspiration and intraoperative smears processed by ultrafast papanicolaou stain.

The Orphan Annie-eyed clear nucleus, defined as a large, optically clear nucleus, devoid of chromatin strands, with sharp chromatin rim, is a more specific feature than are nuclear grooves or intranuclear cytoplasmic inclusions in papillary thyroid carcinoma. In addition, this characteristic nuclear feature is detectable at low magnification. Although these clear nuclei are routinely seen in paraffin sections, they are inconspicuously seen in conventionally processed touch-imprints and fine-needle aspiration (FNA) smears. Among our two institutions, there have been 148 thyroid cases processed by Ultrafast Papanicolaou stain (UFP), including 43 papillary carcinomas, 38 cellular follicular lesions, and 67 cases of nodular hyperplasia. We observed clear nuclei in all of the cases of UFP-processed FNA and intraoperative smears of papillary carcinoma but not of other thyroid lesions. The clear nuclei are most evident in tumor cells with direct contact to the glass slide and are not seen in tumor cells soaked in cystic fluid. UFP is a valuable way to detect Orphan Annie-eyed clear nuclei of papillary thyroid carcinoma early in the diagnostic evaluation, either at immediate on-site evaluation of FNA or at intraoperative consultation and before the availability of permanent sections.