Diagnostic Accuracy of Ultrasound Guided Fine Needle Aspiration Biopsy in Predicting Malignancy in Thyroid Nodules 3cm in Size or Greater

Program: Abstracts - Orals, Poster Previews, and Posters
Session: SAT 270-310-Thyroid Neoplasia (posters)
Clinical/Translational
Saturday, April 2, 2016: 1:15 PM-3:15 PM
Exhibit/Poster Hall (BCEC)

Poster Board SAT 281
Natalie Bernice Teh Ong* and Roberto Cachola Mirasol
St. Luke's Medical Center, Quezon City, Philippines
BACKGROUND

Thyroid nodules are a common problem encountered in endocrine practice. Various reports have shown that majority of these nodules are benign, but in 5 to 15% of cases, these lesions harbor malignancy. Several risk factors for the presence of carcinoma within thyroid nodules have been identified. Though controversial, the prevalence of thyroid carcinoma appears to be associated with larger nodule size. Studies have shown that the diagnostic accuracy of fine needle aspiration biopsy is limited in large nodules prompting recommendations for diagnostic lobectomy regardless of FNAB result.

OBJECTIVE

To determine the diagnostic accuracy of ultrasound guided fine needle aspiration biopsy (USG-FNAB) in predicting malignancy in thyroid nodules 3cm in size or greater.

MATERIALS AND METHODS

Retrospective cohort study of patients whose thyroid nodules were subjected to USG-FNAB followed by thyroidectomy. Nodules were divided into two groups according to their respective sizes. The study group consisted of patients with nodules 3cm in size or greater. Patients with nodules less than 3cm in size were considered as the control group. FNAB cytopathology report was correlated with post thyroidectomy histopathologic diagnosis by nodule dimensions. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy rate, and malignancy rate were computed in each group and were compared.

RESULTS

A total of 3,398 nodules were subjected to USG-FNAB at the Diabetes, Thyroid and Endocrine Center of St. Luke's Medical Center, Quezon City between June 2013 to August 2015. 363 nodules were surgically excised following USG-FNAB. Out of the 363 nodules, 123 (33.9%) measured 3cm in size or greater (study group) and 240 (66.1%) measured less than 3cm in size (control group). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy rate were 47.6%, 93.3%, 88.2%, 62.9%, and 69.9% for the study group and 62.0%, 86.7%, 87.1%, 61.2%, and 72.1% for the control group. Malignancy was observed in 51.2% of the study group and 59.2% of the control group. There was no statistically significant difference between the diagnostic accuracy (p>0.05) and malignancy rate (p=0.148) in both groups.    

CONCLUSION

Increased nodule diameter is not associated with limitations in the diagnostic value of USG-FNAB. Malignancy rate is smaller for larger nodules but did not reach statistical significance.

Nothing to Disclose: NBTO, RCM

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