DIAGNOSIS OF OCCULT THYROID-CARCINOMA BY THYROID ULTRASONOGRAPHY WITHFINE-NEEDLE ASPIRATION CYTOLOGY

OBJECTIVE: To assess the role of ultrasonography and fine needle aspir ation cytology (FNAC) in preoperative diagnosis of,patients with occul t thyroid carcinoma (OTC). STUDY DESIGN: Data on 768 thyroid carcinoma patients receiving primary treatment at Chang Gung Medical Center wer e retrospectively reviewed. Of these patients, 97 had OTC. To detect s mall thyroid nodules early and define the characteristics of clinicall y palpable nodules, thyroid ultrasonography with FNAC were performed o n 67 histopathologically proven OTC patients. Analysis for diagnostic value wits done for ultrasonography and FNAC. RESULTS: In the 67 patie nts receiving ultrasonography with FNAC, 23 were preoperatively diagno sed as having papillary thyroid carcinoma and 1 as having follicular c arcinoma. The tumor size of these 24 preoperative FNAC-proven OTC was 0.81 +/- 0.23 cm (mean +/- SD). In the remaining patients, 10 presente d pictures suspicious for malignancy, with a mean tumor size 0.63 +/- 0.24 cm, and 33 (49.3%) were diagnosed as having benign thyroid lesion s in preoperative FNAC. The tumor size in these 33 lesions was 0.58 +/ - 0.24 cm. Fifty-seven of the 67 OTC patients received frozen sections . Thirty-eight papil lary thyroid carcinomas and four follicular carci nomas were correctly diagnosed on frozen sections. CONCLUSION: Althoug h the rate is not high, high-resolution ultrasonography and FNAC is th e best approach to preoperative diagnosis for OTC patients today.