Fine-needle aspiration (FNA) is the predominant method for triaging thyroid nodules into operative and nonoperative lesions. Accurate needle placement assuring representative sampling of a suspicious nodule is required. Criteria are well established for separation of nodular goiter from most neoplasms but are less well developed for recognition of normal thyroid tissue. Identification of normal tissue is vital when investigating solitary nodules. Cytologic identification of only normal thyroid tissue would indicate a failure to sample the index nodule. The authors investigated a set of criteria to determine whether any were useful for separating goiterous nodules from normal thyroid tissue.
FNA specimens from 10 patients with histologically confirmed goiters were compared with bench aspirates from 7 nodular goiters and 9 thyroid specimens that showed no histologic change. The three sets of specimens were scored for 21 cytomorphologic variables, and differences in the frequency of the variables between sets of FNA specimens were recorded. The patient specimens were compared with bench specimens to find differences secondary only to in vivo and in vitro specimen types. These features were excluded from analysis of differences between bench specimens of hyperplastic nodules and normal tissue.
Cells with feathered cytoplasmic edges occurred with statistically significantly different frequency between bench specimens and patient goiter specimens. Cytomorphologic features that showed differences between FNA specimens from goiters and normal thyroid tissue included the presence of microfollicles, prominent nucleoli, abundant cytoplasm, the number of cells with paravacuolar granules, the presence of Hürthle cells, and the presence of cells with feathered cytoplasmic edges.
The results of the current study indicate that there are cytologic differences between FNA specimens from normal thyroid and from goiterous nodules. The presence of Hürthle cells, prominent nucleoli, and cells with abundant cytoplasm favored the diagnosis of nodular goiter, whereas large numbers of cells with paravacuolar granules favored a determination of histologically normal thyroid. These differences may aid in the distinction of normal thyroid tissue from hyperplastic goiters in cytologic specimens obtained by FNA.