Solitary Thyroid Nodules - Validity of Ultrasonography, Fine Needle Aspiration Cytology and Sestamibi in Detecting Thyroid Malignancies - A Cross-Sectional Study in Kerala

BACKGROUND The diagnosis of thyroid malignancies continues to remain a challenge, due to lack of specificity with various modalities, and intrinsic variability with clinical examination. Although histopathological diagnosis is confirmatory, there is a need for pre-surgical assessment and confirmation, which will prove to be useful in decision making regarding the course of management. The present study was carried out to evaluate the validity of various modalities for detection of thyroid malignancies. METHODS This cross-sectional study was carried out among 40 patients who presented to the outpatient clinic with thyroid nodules. All the participants were evaluated by ultrasound, fine needle aspiration cytology (FNAC) and sestamibi scintigraphy. All the participants were taken up for surgery and the resected specimen was sent for histopathology for confirmatory diagnosis. RESULTS Ultrasound and FNAC detected malignancy in 25 % of the participants, while sestamibi scintigraphy detected malignancy in 30 % of the participants. Based on histopathology, the gold standard confirmatory test, malignancy was detected in 35 % of the participants. It was observed that the sensitivity was highest for FNAC (75 %) followed by TC methoxyisobutylisonitrile (TC MIBI) (50 %). Specificity was highest for FNAC (95 %) followed by ultrasound (88 %) (P < 0.0001). CONCLUSIONS FNAC has the highest sensitivity and specificity while ultrasound and sestamibi have comparable specificity. There is a high probability of malignancy when the delayed image in sestamibi scintigraphy shows retention. MIBI may prove to be useful in differentiating benign and malignant follicular lesions. KEYWORDS Papillary Carcinoma, Histopathology, Thyroid Nodule, Sestamibi, FNAC

Parathyroid Scintigraphy

The visualization of abnormal parathyroid glands is difficult due to their variations in number and localization. Noninvasive parathyroid imaging studies include 99mTc-sestamibi scintigraphy, ultrasonography, computed tomography scanning, magnetic resonance imaging, and positron emission tomography. There is a general consensus that the most sensitive and specific imaging modality, especially when it is combined with single-photon emission CT is the scintigraphy with 99mTc-sestamibi or 99mTc-tetrofosmin. 99mTc-sestamibi scintigraphy significantly increases the role of preoperative scintigraphy in patients with hyperparathyroidism and allows unilateral surgical approach with minimally invasive parathyroidectomy to be used. Generally, three protocols with the use of two radiopharmaceuticals, 99mTc-sestamibi or 99mTc-tetrofosmin, are most widely applied: single-phase dual-isotope subtraction, dual-phase single-isotope and combination of both. Each one of them has specific advantages and disadvantages. While single parathyroid adenomas are localized with greater precision, hyperfunctioning parathyroid hyperplastic cells represent a real challenge to the imaging modalities. Several factors can influence the radionuclide uptake in pathologically changed parathyroid cells, like the size, the level of their functional activity, the quantity of oxyphilic cells, mitochondria, P glycoprotein and other MDR gene products.