Will Real Time Visualization of Needle in Target Thyroid Nodules Minimize False Negative FNA Results?

Abstract

\n Introduction: Prevalence of thyroid nodules in the adult population based on detection by ultrasonography is about 20-76% of which only 5% account for thyroid cancer. All patients with a suspected thyroid nodule either on physical examination or noted incidentally on other imaging should be evaluated with thyroid ultrasound. Any thyroid nodule >= 1 cm on ultrasound should be investigated with FNAC. Ultrasound guided FNAC techniques are used to reduce false negative results. We present a patient with suspicious finding on initial thyroid ultrasound and subsequent negative FNAC presenting a few years later with papillary thyroid cancer. Case Presentation: A 32 y.o. female with history of thyroid nodule and thyroiditis presented to the endocrine clinic for follow-up of her thyroid nodule. 5 years ago, she was diagnosed with thyroid nodule, which was found on an ultrasound scan for workup of her dysphagia. The thyroid ultrasound then showed diffusely heterogeneous thyroid gland with an ill-defined area of decreased echogenicity in the right lobe and left superior lobe and possible nodule in the lower pole left thyroid. Blood work showed TSH of 1.71 (n 0.34-3.00 uIU/ml) and thyroid peroxidase antibody levels was 27.8 (n < 9.0 IU/ml). A CT scan of neck with contrast was done and no concerning mass was seen. The patient had a follow-up ultrasound after 8 months which showed small bilateral thyroid lesions, somewhat ill-defined. The patient had an FNA biopsy of the right thyroid nodule: the results were consistent with a benign follicular nodule. A follow-up thyroid ultrasound was done in a year, and the findings were unchanged. The patient came back 3 years later for follow-up with complaints of a new palpable nodule in the neck. Ultrasound showed unchanged right thyroid nodule and some new cervical adenopathy. The ultrasound showed a 2.2 cm heterogeneous lymph node with punctate echogenic foci along the right lateral margin of the right internal jugular vein at the level of the thyroid gland, Subsequently FNA biopsy of the right cervical node and right thyroid node were done. The cells from lymph nodes were positive for malignancy and cells from the right thyroid nodule were atypical. Overall the appearance was consistent with papillary thyroid carcinoma. Subsequently the patient underwent total thyroidectomy and right modified lymph node dissection and the pathology results came back as multifocal papillary thyroid cancer right side 1.2 cm and left side 0.4 cm, with metastasis to 2 lymph nodes. Conclusion: The reported false negative rate of ultrasound-guided FNAC is variable. Success of US-FNA depends on experience of operator and cyto-pathologist and the intrinsic nature of the nodule. Malignancy rates of only 1-2% are reported with repeat FNA in prior benign nodules. Good FNA techniques and real-time visualization of needle in target nodules can further decrease false negatives.