Large-needle aspiration biopsy for the preoperative selection of follicular adenoma diagnosed by fine-needle aspiration as a microfollicular nodule or suspected cancer

The preoperative fine-needle aspiration (FNA) cytologic diagnoses of microfollicular nodule and suspected cancer include nodules that yield histologic results of typically benign lesions, nodular hyperplasia and follicular adenomas, and differentiated thyroid cancer postoperatively. We reviewed the clinical and pathologic data for patients with palpable thyroid nodules with these two cytologic diagnoses; nodules were also examined by large-needle aspiration biopsy (LNAB) to assess whether the distinction achieved by LNAB in pure microfollicular or mixed microfollicular-macrofollicular nodules could be used preoperatively to better predict the diagnosis of follicular adenoma. One hundred fourteen nodules of this type were excised. Postoperative results were grouped in nodular hyperplasia (90 nodules), follicular adenoma (8), and differentiated carcinoma (16). The prevalence of the follicular adenoma and thyroid carcinoma postoperative findings was 33% among the microfollicular nodules and 5.9% among the microfollicular-macrofollicular nodules at preoperative LNAB, (p = 0.0004). Within the postoperatively benign nodules, the prevalence of follicular adenoma was 14.3% among the microfollicular nodules and 2% among the microfollicular-macrofollicular nodules at LNAB (p = 0.028). These data indicate that histologic examination of the LNAB specimen can be used to identify those thyroid nodules diagnosed by FNA as microfollicular nodules or suspected cancer, which are most likely to be follicular adenomas postoperatively.