Diagnostic aspiration of parathyroid adenomas causes severe fibrosis complicating surgery and final histologic diagnosis

Objective: To determine whether fine-needle aspiration (FNA) of parathyroid adenomas may cause a severe fibrotic reaction of the gland and surrounding structures, making surgery more difficult and histology more confusing. Design: A study was conducted over a 33-month period to compare the operative findings of 30 patients who underwent FNA of a parathyroid adenoma to those of 3000 patients who had not had their parathyroid tumor aspirated. Each patient's normal parathyroid glands also served as internal controls. All aspirations were performed by referring physicians under direct ultrasound guidance within 3 months of surgery, and all adenomas were located in routine positions. Patients who had previous thyroid or parathyroid surgery were not included. Patients with secondary or tertiary hyperparathyroidism were not included. Main outcome: The control group (non-FNA) showed a fibrotic reaction in 127 (4.3%) tumors appreciated by the surgeon and recognized on histology. In contrast, tumors undergoing FNA had a dense and often severely fibrotic reaction seen at surgery in 19 of 30 (63%) (p < 0.0001) and on histology in 23 of 30 (77%) (p < 0.0001). The fibrotic reaction appeared to mimic malignancy on histology and increased in occurrence with increased numbers of aspiration passes and larger needle bore (p < 0.05). No normal glands (n> 7500) or hyperplastic glands (n = 488) demonstrated fibrosis in any patient. Tumors that were aspirated required an eightfold increase in time to remove (p < 0.005) and more than doubled the total operative time (p < 0.05). Conclusions: FNA of parathyroid adenomas can cause a severe fibrotic process that typically involves adjacent tissues. This reaction dramatically increases the difficulty of surgical resection, often requiring microdissection techniques to preserve nerves and assure complete removal. The fibrosis can cause confusing histology mimicking malignancy. FNA of parathyroid adenomas should be avoided unless absolutely necessary.