Fine-needle aspiration of the thyroid: correlating suspicious cytology results with histological outcomes

Fine-needle aspiration cytology (FNAC) assists the diagnosis of thyroid malignancy. A 'suspicious for malignancy' on FNAC creates a management dilemma. The aims of this study were to investigate the malignancy rate for patients with suspicious cytology, and to describe a management approach for those with a suspicious result.

A retrospective review of prospectively collected data in an endocrine surgery database was undertaken. Patients undergoing thyroidectomy with preoperative FNAC from 1992 to 2012 were analysed.

Preoperative FNAC was undertaken in 2,692 patients, and the FNAC result was 'suspicious for malignancy' in 94 (3.5 %) patients. Of these, 53 (56.4 %) were malignant, with the majority 44 (83.0 %) being papillary thyroid cancer. 48 patients went straight to total thyroidectomy, 40 patients had an initial diagnostic hemithyroidectomy, and 1 patient had a diagnostic isthmusectomy. 5 patients required reoperative total thyroidectomy as an initial procedure. Of the 94 suspicious cases, 55 were reported by an unknown, presumably non-expert, thyroid cytopathologist. 38 of these cases were available for review and re-reporting by an experienced cytopathologist. On review, 28 (73.7 %) were reclassified as cytologically malignant, and all of these were confirmed as malignant on subsequent histopathology.

Suspicious cytology has a high risk of malignancy. Expert thyroid cytopathology can improve diagnostic accuracy and a preoperative malignant diagnosis should be pursued to enable one-stage surgery where possible.