الفهرس 
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Abstract
Intraoperative frozen section (IFS) had been, historically, the main tool to determine the initial histologic diagnosis of a thyroid nodule and therefore to guide the treatment strategy. Surgery could be limited to a hemi-thyroidectomy in case of a benign nodule, while a malignant IFS diagnosis indicates a total thyroidectomy. Since the advent of preoperative fine needle aspiration (FNA), and its establishment as a mainstay in the preoperative exploration of thyroid nodules, the role of IFS in this setting has been widely questioned. The introduction in 2007 of the Bethesda system for reporting thyroid cytopathology (BSRTC) has improved FNA reporting standards and became a standard of practice.
The widespread use of this system has substantially simplified the cytopathologic diagnosis and subsequent management of thyroid nodules. In fact, in this system, there are six diagnostic categories: Non-diagnostic or unsatisfactory (Bethesda I), benign (Bethesda II), atypia of undetermined significance or follicular lesion of undetermined significance (Bethesda III), follicular neoplasm or suspicious for a follicular neoplasm (Bethesda IV), suspicious for malignancy (Bethesda V), and malignant ((Bethesda VI). Each of these diagnostic categories is linked to an implied risk of malignancy, ranging from 0 to 3% for the benign category to virtually 100% for the malignant category. Naturally, depending on that risk, the treatment could vary from simple surveillance to total thyroidectomy.
This study aimed to determine accuracy and intertest agreement of preoperative fine-needle aspiration cytology (FNAC) and intraoperative frozen-section analysis (IFS) findings in thyroid surgery, and to assess the influence of intraoperative FS findings on decision making and the utility of IFS in solitary thyroid nodules.
Type of Study: A retrospective and prospective cohort comparative clinical study.
Study Setting: This study will be conducted at (General surgery department), Ain Shams University Hospitals. Approval of the Ethical Committee and written informed consent from all participants will be obtained.
Study Period: Between November 2020 and November 2023.
The current study results group A (n=20) and group B (n=20) were assessed for demographic, baseline, hematological, biochemical, and preoperative characteristics to ensure equivalence prior to interventions. Results revealed no statistically significant differences in age distribution (p=0.868) or gender composition (p=0.327), indicating matched groups. Thyroid function tests (T3, T4, TSH) showed no significant variations (p=0.820, p=0.081, p=0.567). Hematological and biochemical parameters (hemoglobin, creatinine, ALT, AST, INR) exhibited no significant disparities (p=0.420, p=0.811, p=0.752, p=0.571, p=0.862). Preoperative characteristics (family history, TIRADS, nodule size, site) were well-balanced (p=0.519, p=0.752, p=0.625, p=0.321). These findings support valid outcome comparisons, enabling assessment of thyroid surgery interventions without baseline confounders.
Both group A and group B, each with 20 participants, underwent fine-needle aspiration cytology (FNAC) uniformly, ensuring consistent preoperative cytological assessment. FNAC results, categorized by the Bethesda System, showed no statistically significant differences between groups despite slight variations in specific categories. In group A, all participants underwent intraoperative frozen section analysis, impacting surgical decision-making: 30% benign, 30% malignant, and 40% follicular patterns. This guided decisions for hemithyroidectomy (55%) or completion thyroidectomy (45%). Conversely, group B did not undergo intraoperative frozen section analysis, resulting in a higher proportion of benign diagnoses (65%) compared to group A (40%).
The current study showed Paraffin section results compared to intraoperative frozen section (IFS) findings reveal diagnostic accuracy challenges. IFS underestimated malignancy in 22.2% of initially benign nodules but predicted malignancy accurately in 55.6% of initially diagnosed cases. However, IFS struggles to differentiate benign from malignant follicular-patterned lesions (54.5% benign, 22.2% malignant) without capsular or vascular invasion, requiring detailed paraffin analysis for definitive management decisions.
The correlation between Fine-Needle Aspiration Cytology (FNAC) results and definitive paraffin section outcomes highlights the diagnostic precision and limitations of preoperative FNAC in predicting thyroid nodule pathology. Bethesda I (Non-diagnostic/Unsatisfactory) results show a relatively balanced distribution between benign and malignant outcomes in paraffin sections, indicating the uncertainty with this category. Bethesda III (Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance) and Bethesda IV (Follicular Neoplasm/Suspicious for a Follicular Neoplasm) categories primarily correlate with benign paraffin results, suggesting a cautious approach to surgery may be warranted in many cases within these categories. However, the transition to Bethesda V (Suspicious for Malignancy) significantly increases the likelihood of a malignant paraffin diagnosis, underscoring its high predictive value for malignancy. This analysis underscores the critical role of FNAC Bethesda classification in guiding clinical decision-making and surgical planning for thyroid nodules.
The comparison between group A, who underwent intraoperative frozen section (IFS), and group B, who did not, based on their preoperative Fine-Needle Aspiration Cytology (FNAC) results specifically within the Bethesda III (AUS/FLUS - Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance) and Bethesda IV (FN/SFN - Follicular Neoplasm or Suspicious for a Follicular Neoplasm) categories, reveals a distribution leaning towards Bethesda III and IV diagnoses in both groups, with no statistically significant difference (p-value = 0.349). group A had 60% of cases classified as Bethesda III and 40% as Bethesda IV, while group B had 50% in each category. This indicates a similar distribution of these diagnostic categories between patients selected for IFS and those who were not, suggesting that the decision to perform IFS was not biased by the FNAC results within these categories..
The analysis of the correlation between Fine Needle Aspiration Cytology (FNAC) alone and FNAC followed by a frozen section with respect to final paraffin section results in cases with a follicular pattern reveals that there is no significant difference in diagnostic outcomes between these two approaches. Specifically, for benign cases (n=15), FNAC alone identified 33.3% as benign, while FNAC followed by a frozen section identified 20% as benign. For malignant cases (n=5), both FNAC alone and FNAC followed by a frozen section identified 40% as malignant. The test value, with a p-value of 0.326, indicates that there is no statistically significant difference in the effectiveness of FNAC alone versus FNAC followed by a frozen section in predicting the final histopathological diagnosis. This suggests that adding a frozen section to FNAC does not significantly improve diagnostic accuracy for follicular pattern lesions when compared to FNAC alone, highlighting the inherent limitations of preoperative and intraoperative diagnostic tools in accurately distinguishing between benign and malignant follicular thyroid lesions.