Clinical relevance of non-palpable thyroid nodules as assessed by ultrasound-guided fine needle aspiration biopsy

It is known from autopsy data that thyroid nodules are far more common than can be detected by palpation alone. With the wide use of modern non-invasive imaging many non-palpable thyroid nodules are discovered but the proper approach to these nodules is still debatable. In a retrospective study, we reviewed the data from 186 US-guided FNA biopsies (US-FNAB) performed between May 1995 and March 1997 at the Sapir Medical Center, Israel, a iodine-sufficient urban area. Sixty-one of the 186 US-FNAB of the thyroid were performed in non-palpable nodules. The mean size of these nodules was 2.4±1.0 cm (mean±SD) ranging from 1.1-5.5 cm. Description of the nodule consistency was available in 53 cases; 42/53 were solid and 11/53 were solid-cystic. FNAB was diagnostic in 46 patients and non-diagnostic in 15. Forty-three of the diagnostic cytology reports were benign, one revealed papillary carcinoma, one had suspicious findings and the third was suspicious for a follicular neoplasm. The last two patients were referred to surgery and a follicular adenoma was found in both. Among the 61 non-palpable thyroid nodules, only one was papillary carcinoma, a prevalence of 1.6%. The other two patients referred to surgery had benign lesions. We found a low prevalence of malignancy in relatively large non-palpable thyroid nodules.