Nuclear grooves: a useful criterion in the cytopathologic diagnosis of papillary thyroid carcinoma

A recent report emphasized the usefulness of the grooved nucleus as a diagnostic criterion of papillary thyroid carcinoma (PTC) in histopathologic material. The present study was undertaken to evaluate whether grooved nuclei can serve as an additional diagnostic criterion for PTC in cytologic material obtained by fine-needle aspiration (FNA). Slides from 124 consecutive thyroid FNAs were reviewed. Specimens included 11 PTCs, one follicular carcinoma, six follicular adenomas, eight follicular neoplasms not otherwise specified, 10 cases of chronic thyroiditis, and 88 colloid nodules/adenomatous goiters. Among the PTC cases, grooved nuclei were found in all 11 (100%), intranuclear inclusions in nine (82%), papillary fragments in seven (64%), and psammoma bodies in two (18%). Nuclear grooves were also observed in two of the 113 non-PTC cases (1.8%), both of which were colloid nodules, one with extensive Hurthle-cell change. The grooved nuclei were best identified on Papanicolaou-stained material. They were inconspicuous and difficult to identify in air-dried Diff-Quik-stained material. It appears that the recognition of grooved nuclei among tumor cells is a valuable diagnostic feature of PTC in cytologic material stained with polychromatic Papanicolaou stain.