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

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Abstract
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 nonpalpable 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 nonpalpable thyroid nodules.