Pattern of thyroid lesions and role of fine needle aspiration cytology (FNA) in the management of thyroid enlargement: a retrospective study from a teaching hospital in Riyadh

The study aims to determine the cytological pattern of thyroid lesions, in addition to the utility and accuracy of fine needle aspiration (FNA) cytology as an initial diagnostic method in the investigation of these lesions among Saudi patients. Four hundred and seventy-nine (479) FNAs were performed on patients presenting with diffuse or nodular thyroid enlargement to the endocrinology clinic at King Khalid University Hospital in Riyadh during the period September 1993 to September 1996. The results of the FNA and the 125 histological diagnoses obtained from the subsequent partial and subtotal thyroidectomies were retrospectively and independently reviewed and compared by two cytopathologists. The results of the FNA cytological diagnosis showed that 372 patients (77.7%) had benign lesions, 24 (5%) had lesions which were suspected of malignancy, 25 (5.2%) had malignant neoplasms, and 58 (12.1%) had FNAs which were inadequate for cytological assessment. Colloid and adenomatous nodules were the most common benign lesions reported (47.8%). Papillary carcinoma was the most common malignant neoplasm (4.2%). Despite the relatively limited number of patients who underwent surgery, cytohistopathology combined with statistical analysis of the results showed that our FNA accuracy rate is in the region of 94.4% with a sensitivity of 78% and a specificity of 100%. In addition, the negative predictive value (NPV) and the positive predictive value (PPV) of FNA thyroid cytology were 93% and 100% respectively. Our findings indicate that FNA cytology can be used effectively in the evaluation of both nodular and diffuse thyroid lesions whilst cytopathologist should be aware of the potential diagnostic pitfalls and the limitations of the procedure in the diagnosis of follicular, cystic, and small neoplasms, the positive identification of thyroiditis and most cases of neoplasia by itself provides justification for FNA.