Aspiration needle biopsy refines preoperative diagnosis of thyroid nodules defined at fine needle aspiration as microfollicular nodule.

The aim of this paper was to verify the hypothesis that large needle biopsy performed preoperatively can refine preoperative fine needle aspiration (FNA) cytological diagnoses of microfollicular nodules. Since 1980 we have been using FNA and aspiration needle biopsy (ANB) (18 or 16 gauge needles) to select for surgery all euthyroid patients with palpable thyroid nodules referred to our department. From 1980 to 1994, 6,124 patients (12% male, 88% female) with thyroid nodules (71% single, 29% multiple) were examined by FNA; 29% of these patients were also examined preoperatively by ANB histology. Of all the nodule patients examined, 371 received a preoperative FNA diagnosis of microfollicular nodule. Two hundred and fifty-four of these nodules (68%) were also examined preoperatively by ANB. Unsatisfactory ANB specimens constituted 17% of cases; pure microfollicular structure was confirmed by ANB in 36% of the nodules; ANB showed the remaining 47% to contain a macrofollicular component, thus suggesting a benign hyperplastic lesion. Twelve nodules which were found to be microfollicular at FNA cytology and micro-macrofollicular at ANB were excised and were subsequently determined as benign at definitive postoperative histology. These data indicate the utility of ANB in refining the preoperative FNA diagnosis of microfollicular nodule and in preoperatively identifying benign hyperplastic mixed micro-macrofollicular lesions which can be followed by observation.