Specimen adequacy and diagnostic specificity of ultrasound-guided fine needle aspirations of nonpalpable thyroid nodules.

Ultrasound-guided fine needle aspiration (USG-FNA) is a safe, effective, and dependable test used to assess thyroid nodules. However, the size of the lesion can adversely affect the outcome of the procedure. The aim of this study was to assess specimen adequacy and diagnostic specificity in USG-FNA of thyroid nodules measuring < or = 1.5 cm. A total of 219 thyroid FNAs were performed in a one year; 26 were obtained by pathologists, 139 by clinicians, and 54 by radiologists under ultrasound guidance. Of the 54 ultrasound-guided aspirates, 19 cases (35%) were performed on nodules < or = 1.5 cm (range 0.8-1.5 cm, mean 1.3 cm). Cytologic material from these 19 cases was reviewed along with corresponding available follow-up surgical material. Standard criteria for specimen adequacy and established morphologic criteria for diagnostic specificity were assessed in each case. All 19 cases met criteria for specimen adequacy, and in 17 cases (89%) specific cytologic diagnoses were made (cellular/adenomatous nodule--2 cases, colloid nodule--10 cases, Hashimoto's thyroiditis--4 cases, and papillary cystic carcinoma--1 case). The diagnoses were confirmed by surgical follow-up in six cases including the case of papillary carcinoma. One case diagnosed as suspicious for a papillary carcinoma subsequently was found to be a follicular adenoma by histology. In one case, a diagnosis of lymphocytic thyroiditis versus intrathyroidal lymphoid tissue was made (See Table I). In majority of cases of USG-FNA of nonpalpable thyroid nodules, adequate material may be obtained for a specific cytopathologic diagnosis.