Diagnostic value of Bethesda system for reporting thyroid cytopathology in patients with prior thyroid surgery

Sevgul Faki; Gulsum Karahmetli; Yazgan Aylin Kilic; Mehmet Kiliç; Oya Topaloglu; Didem Ozdemir; Reyhan Ersoy; Bekir Cakir

doi:10.1530/endoabs.70.AEP973

Background: Fine needle aspiration biopsy (FNAB) and Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) have proven to be the most valuable diagnostic procedure for preoperative discrimination of benign and malignant thyroid nodules. Thyroid surgery may cause regional scarring and some degree of fibrotic process which may result in problems when collecting FNAB samples and evaluating the cellular abnormalities. In this study, we aimed to determine whether the Bethesda classification system in thyroid nodules is reliable in patients with a history of thyroid surgery.

Methods: We retrospectively examined outcomes of 130 patients with 260 nodules who underwent a thyroidectomy for recurrent goiter (Group 1) and compared them with 2821 patients with 5890 thyroid nodules who underwent first thyroidectomy (Group 2) in our center between 2007 and 2014.

Result: Malignancy rate was significantly lower in group B (24 (18.5%) patients) compared to group A (911 (32.3%) patients) (P = 0.016). The most frequent operation indications in group A may explain the hight rate ofmalignancy in this group, that were giant nodule and suspicious cytology results in group B and group A respectively (P = 0.001). Hypothyroidism was significantly higher in group B and result by a hight ratio of gaint nodules (P = 0.001). Although a relationship between giant nodule and higher malignancy rate was reported in previous studies, we did not find a correlation between giant nodules and malignancy rate of patient in group B. Diagnostic value of Bethesda was determined in patients with primary and reoperative thyroid surgery. Benign cytology was considered negative and suspicious for malignancy and malignant cytologies were considered positive. sensitivity, specifity, PPV, NPV and accuracy of Bethesda classification in patients with primary thyroid surgery were 74.50%, 98.18%, 83.38%, 96.92% and 95.60%, respectively. In patients with reoperative thyroid surgery, sensitivity was 62.50%, specifity was 98.91%, PPV was 71.43%, NPV was 93.38% and accuracy was 97.39%.

**Table 1** Diagnostic value of Bethesda classification in patients who underwent primary and reoperative thyroid surgery.
Primary			Reoperative
	a (n = 3710)	b (n = 3814)	a (n = 192)	b (n = 199)
Sensitivity	74.50%	76.37%	62.50%	66.66%
Specifity	98.18%	96.09%	98.91%	95.79%
Positive predictive value	83.38%	71.61%	71.43%	42.86%
Negative predictive value	96.92%	96.92%	98.38%	98.38%
False positive	16.62%	28.38%	28.5%	57.14%
False negative	3.07%	3.07%	1.62%	1.62%
Accuracy	95.60%	93.83%	97.39%	94.47%

Conclusion: FNAB is known to be the most accurate and cost-effective method that provides avoidance of unnecessary surgery in 25% of patients with benign thyroid disease. A lower frequency of malignancy was observed in patients/nodules with reoperative thyroid surgery compared to patients/nodules with primary thyroid surgery in this surgical series. Sensitivity and PPV of Bethesda were affected negatively by previous thyroid surgery. This might be considered in these patients while deciding for a recurrent surgery which has a higher risk of complications.

Endocrine Abstracts

AEP973