Role of Diagnostic 131I SPECT/CT in Long-Term Follow-up of Patients with Papillary Thyroid Microcarcinoma

The Role of Risk Factors for the Progression of Patients with T1b-T2 Papillary Thyroid Carcinoma (PC) during Long-Term Follow-Up

Background/Objectives: Recurrence prediction for patients with PC and tumor sizes ranging between 1 and 4 cm, classified as T1b and T2, remains a controversial problem. We evaluated which risk factors, identified during the primary tumor surgery, might play a prognostic role in predicting disease progression. Methods: We retrospectively enrolled 363 patients with classic PC who were in follow-up (207 T1b, 156 T2), with tissue risk factors at surgery in 209/363 cases. In all cases, an 131I-whole-body scan, SPECT/CT, and US were employed to detect any metastases during follow-up, and histology was used to confirm lesions. In the absence of surgery, metastases were validated by radioisotopic and radiologic procedures, eventually culminating in a needle biopsy and sequential thyroglobulin changes. Results: Metastases occurred in 61/363 (16.8%) patients (24 T1b, 37 T2). In 50/61 cases, the following risk factors were identified: minimal extrathyroid tumor extension (mETE) alone in 12/50 patients, neck lymph node (LN) metastases in 8/50 cases, and multifocality/multicentricity (M/M) in 6/50 cases. In the remaining 24/50 cases, the risk factors were associated with each other. From a Cox regression multivariate analysis, metastasis development was significantly (p < 0.001) influenced by only mETE and LN metastases, with a shorter disease-free survival (log-rank test). Conclusions: The current study proves that mETE and neck LN metastases are associated with aggressive PC. While LN metastasis' role is known, mETE's role is still being debated, and was removed by the AJCC's eighth edition because it was considered to not be associated with an unfavorable prognosis. However, this interpretation is not supported by the present study and, according to comparable studies, we suggest a revision of the mETE classification be considered in the next AJCC edition.

Clinical Implications of Adding SPECT/CT to Radioiodine Whole-Body Scan in Patients With Differentiated Thyroid Cancer: A Systematic Review and Meta-analysis

PURPOSE

This study aimed to determine the usefulness of adding SPECT/CT to radioiodine whole-body scans (WBSs) for the treatment of differentiated thyroid cancer (DTC).

PATIENTS AND METHODS

A systematic review and meta-analysis were performed following the PRISMA guidelines (PROSPERO registration: CRD42022341732) to compare the feasibility of conclusive readings and the frequency of changes in treatment plans in patients with DTC undergoing WBS + SPECT/CT versus WBS. MEDLINE, EMBASE, and Cochrane databases were searched to identify relevant articles concerning thyroid cancer, radioactive iodine, and SPECT/CT or SPECT, published before August 16, 2023. Studies not comparing WBS + SPECT/CT with WBS, those lacking target outcomes, and those not involving human subjects were excluded. The risk of bias was assessed using the RoBANS 2.0 (Risk of Bias Assessment Tool for Nonrandomized Studies) tool. The GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) system was used to evaluate the quality of evidence and strength of recommendations.

RESULTS

A total of 30 studies (prospective n = 9, retrospective n = 21) were included in the meta-analyses. Adding SPECT/CT to WBS was shown to increase conclusive readings for cervical lesions, extracervical lesions, and all regions. Lesion-based analyses showed improvements of 14%, 20%, and 18%, respectively, whereas scan-based analyses showed improvements of 27%, 9%, and 34%. The addition of SPECT/CT to WBS led to changes in 30% of treatment plans after diagnostic scans and 9% of treatment plans after posttherapeutic scans. The quality of evidence and strength of recommendations were low.

CONCLUSIONS

Compelling evidence demonstrates that the addition of SPECT/CT to WBS improves lesion localization, diagnostic performance, and therapy plan for patients with DTC.

Minimal Extrathyroid Extension (mETE) as the Only Risk Factor in Patients with Papillary Thyroid Carcinoma (PC): Its Clinical Impact on Recurrence and Outcome during Long-Term Follow-Up

Minimal extrathyroid extension (mETE) effect on papillary thyroid carcinoma (PC) prognosis is still debated even more so now that this factor has been removed in the 8th AJCC Edition, supporting the hypothesis that mETE is not associated with aggressive tumors. We retrospectively enrolled 91 PC patients (Group 1) submitted to total thyroidectomy and radioiodine ablation. At the time of the primary tumor surgery, mETE was ascertained in all patients with no other risk factors, such as multifocality, vascular invasion, neck and distant metastases, and aggressive histological variants. As controls, 205 consecutive matched PC patients (Group 2) without mETE and the aforementioned risk factors were enrolled. During the follow-up (average 8 years), 16/91 (17.58%) Group 1 patients and 15/205 (7.32%) Group 2 patients developed metastases (p = 0.0078). Cox regression analysis showed an increased risk of metastases in patients with mETE (HR: 2.58 (95% CI 1.28-5.22) p = 0.008). Disease-free survival (DFS) was significantly lower in patients with mETE than in controls (p = 0.0059). The present study seems to demonstrate that mETE can be associated with an aggressive PC and can be considered, even alone without other risk factors, an independent factor of unfavorable DFS. Thus, by excluding mETE in the 8th AJCC Edition, patient care and management could be compromised.

The clinical and pathological significance of increased expression of the cannabinoid receptors CB-1R and CB-2R in patients with papillary thyroid carcinomas compared to benign thyroid lesions

INTRODUCTION

Papillary thyroid carcinoma is the most common malignancy of the endocrine system. Most papillary thyroid carcinoma patients enjoy excellent outcomes. However, in patients with biologically aggressive features, additional prognostic and predictive data may aid disease management. Dysregulation of the endocannabinoid system including the cannabinoid receptors 1 and 2 (CB-1R and CB-2R) during carcinogenesis has been extensively studied over the last few decades. The aim of this study was to evaluate immunohistochemically the expression levels of both receptors in patients with papillary thyroid carcinoma and benign diseases, and to compare these rates and the histopathologically and clinically prognostic features.

METHODS

The pathological materials and clinical data of 100 patients with papillary thyroid carcinoma and 40 with benign diseases were retrospectively re-evaluated. All tissues were immunohistochemically stained for CB-1R and CB-2R. The expression levels of CB-1R and CB-2R in papillary thyroid carcinomas, and benign lesions were recorded and compared with the pathological and clinical features.

RESULTS

The expression levels of both receptors were significantly higher in papillary thyroid carcinoma patients than in those with benign conditions (P = 0.001). CB-1R expression correlated with both extrathyroidal extension (P = 0.022) and capsular invasion (P = 0.001). CB-2R expression was associated with the risk group of the American Thyroid Association stratification system (P = 0.004).

CONCLUSION

Our study suggests that increased cannabinoid receptor expression contributes to thyroid carcinogenesis. The CB-2R expression level could provide additional information aiding risk management. Furthermore, the CB-1R and CB-2R antibodies might increase the accuracy of papillary thyroid carcinoma diagnosis when combined with the papillary thyroid carcinoma biomarkers assayed after fine-needle aspiration of neoplastic cells.

Hashimoto's Thyroiditis and Papillary Thyroid Carcinoma: A Follow-Up Study in Patients with Absence of Aggressive Risk Factors at the Surgery of the Primary Tumor

Hashimoto's thyroiditis (HT) is often associated with papillary thyroid carcinoma (PC); it is still a matter of controversy whether the behavior of carcinoma is more aggressive or not. During the follow-up, we retrospectively enrolled 97 patients with PC/HT after thyroidectomy without risk factors at the surgery of the primary tumor, such as multifocality/multicentricity, extrathyroid tumor extension, vascular invasion, neck and distant metastases, and aggressive histological variants. HT diagnosis was confirmed by histology and serum thyroid antibodies. Tumor size was ≤10 mm in 64 cases (microcarcinomas); 206 matched PC patients after thyroidectomy without HT and risk factors were enrolled as controls, totaling 122 microcarcinomas. During follow-up, metastases occurred in 15/97 (15.5%) PC/HT cases, eight microcarcinomas, and in 16/206 (7.8%) without HT, eight microcarcinomas (p = 0.04). Considering both PC/HT and PC patients without HT who developed metastases, univariate analysis showed an increased risk of metastases in patients with HT coexistence, OR: 2.17 (95% CI 1.03-4.60) p = 0.043. Disease-free survival (DFS) was significantly (p = 0.0253) shorter in PC/HT than in the controls. The present study seems to demonstrate that HT is not a cancer protective factor in PC patients given the less favorable outcomes and significantly shorter DFS. HT may also represent an independent recurrence predictor without other risk factors.

A Comparative Follow-Up Study of Patients with Papillary Thyroid Carcinoma Associated or Not with Graves' Disease

Whether papillary carcinoma (PC) behavior is more aggressive in Graves’ disease (GD) patients than PC cases without GD is controversial. We retrospectively enrolled 33 thyroidectomized PC/GD patients during long-term follow-up, 23/33 without risk factors at surgery, and 18/33 microcarcinomas; 312 PC euthyroid-matched patients without risk factors served as controls. A total of 14/33 (42.4%) PC/GD patients, 4 with and 10 without risk factors at diagnosis, 6 with microcarcinoma, underwent metastases during follow-up. In controls, metastases in 21/312 (6.7%) were ascertained. Considering 10/23 PC/GD patients and 21/312 controls without risk factors who developed metastases, univariate analysis showed that there was an increased risk of metastasis appearance for PC/GD cases (p < 0.001). Disease-free survival (DFS) was significantly (p < 0.0001, log-rank test) shorter in PC/GD patients than in controls. Significantly more elevated aggressiveness in 6/18 PC/GD patients with microcarcinoma than in controls was also ascertained with shorter DFS. Thus, in the present study, PC/GD had aggressive behavior during follow-up also when carcinoma characteristics were favorable and some cases were microcarcinomas. GD and non-GD patient comparison in the cases without risk factors at diagnosis showed an increased risk to develop metastases in GD during follow-up, suggesting that GD alone might be a tumor aggressiveness predictive factor in these cases.

BAX gene (-248 G > A) polymorphism in a sample of patients diagnosed with thyroid cancer in the Federal District, Brazil

INTRODUCTION

Papillary thyroid cancer corresponds to approximately 1% of all carcinomas; nevertheless, it is the most prevalent endocrine neoplasm in the world. Studies reveal that the BAX (-248 G > A) polymorphism may be associated with negative regulation of BAX gene transcription activity, causing a decrease in its protein expression.

OBJECTIVE

The present study aimed to describe the genotype and allele frequencies of BAX single nucleotide polymorphisms (-248 G > A) (rs4645878) in the research patients, and to associate its presence with susceptibility to papillary thyroid cancer.

METHODS

This case-control study was conducted with 30 patients with papillary thyroid cancer. For the evaluation of genetic polymorphisms, the polymerase chain reaction-restriction fragment length polymorphism technique was employed. Allele and genotype frequencies were estimated using the SPSS program, and significant associations were considered when p < 0.05.

RESULTS

There was a significant genotypic difference between papillary thyroid cancer and the control group (p = 0.042). The GG genotype provided a protective factor for papillary thyroid cancer (p = 0.012, odds ratio (OR) = 0.313; confidence interval (CI) = 0.123-0.794). Likewise the G allele was a protective factor for papillary thyroid cancer (p = 0.009; OR = 0.360; CI = 0.163-0.793). The BAX gene polymorphism (-248 G > A) was associated with papillary thyroid cancer.

CONCLUSION

BAX (-248 G > A) GG genotype carriers, or at least one mutated allele, was associated with papillary thyroid cancer in the Brazilian population studied, and the G allele presence is considered a protective factor against papillary thyroid cancer occurrence.

Circ_0039411 promotes papillary thyroid carcinoma development through mediating the miR-423-5p/SOX4 signaling

BACKGROUND

Papillary thyroid carcinoma is the most frequent histological subtype of thyroid cancer with a high incidence. We aimed to explore the function of circular RNA_0039411 (circ_0039411) and its associated mechanism in papillary thyroid carcinoma progression.

METHODS

Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot assay were conducted to determine the expression of RNA and protein, respectively. The colony formation ability, migration, invasion, and apoptosis were analyzed by colony formation assay, transwell migration assay, transwell invasion assay, and flow cytometry. Cell glycolytic metabolism was analyzed using fluorescence-based glucose assay kit and fluorescence-based lactate assay kit. Dual-luciferase reporter assay and RNA-Pull-Down Assay were performed to validate the binding between microRNA-423-5p (miR-423-5p) and circ_0039411 or SRY-box transcription factor 4 (SOX4). The xenograft tumor model was used to assess the role of circ_0039411 in the tumor growth in vivo.

RESULTS

Circ_0039411 was highly expressed in papillary thyroid carcinoma tissues and cell lines compared with adjacent normal tissues and NTHY-ORI3.1 cells. Circ_0039411 interference suppressed the colony formation ability, migration, invasion, and glycolysis but promoted the apoptosis of papillary thyroid carcinoma cells. MiR-423-5p was a target of circ_0039411 in papillary thyroid carcinoma cells. Circ_0039411 knockdown-mediated effects in papillary thyroid carcinoma cells were largely overturned by the silence of miR-423-5p. MiR-423-5p bound to the 3' untranslated region (3'UTR) of SOX4. SOX4 overexpression largely reversed circ_0039411 silencing-mediated effects in papillary thyroid carcinoma cells. Circ_0039411 positively regulated SOX4 expression by sponging miR-423-5p in papillary thyroid carcinoma cells. Circ_0039411 silencing notably suppressed the growth of xenograft tumors in vivo.

CONCLUSION

Circ_0039411 promoted the malignant behaviors of papillary thyroid carcinoma cells partly depending on the regulation of the miR-423-5p/SOX4 axis.

The Diagnostic Usefulness of 131I-SPECT/CT at Both Radioiodine Ablation and during Long-Term Follow-Up in Patients Thyroidectomized for Differentiated Thyroid Carcinoma: Analysis of Tissue Risk Factors Ascertained at Surgery and Correlated with Metastasis Appearance

¹³¹I Single-photon emission computerized tomography/computerized tomography (SPECT/CT) in the management of patients thyroidectomized for differentiated thyroid carcinoma (DTC) was further investigated. Retrospectively, 106 consecutive DTC patients were enrolled at the first radioiodine ablation, 24 at high risk (H), 61 at low risk (L) and 21 at very low risk (VL). ¹³¹I whole-body scan (WBS) and SPECT/CT were performed after therapeutic doses using a hybrid dual-head gamma camera. At ablation, SPECT/CT correctly classified 49 metastases in 17/106 patients with a significantly (p < 0.001) more elevated number than WBS which evidenced 32/49 foci in 13/17 cases. In this case, 86/106 patients could be monitored in the follow-up including 13/17 cases with metastases already at post-therapeutic scans. SPECT/CT after radioiodine diagnostic doses more correctly than WBS ascertained disease progression in 4/13 patients, stable disease in other 4/13 cases and disease improvement in the remaining 5/13 cases. Further 13/86 patients with only residues at post-therapeutic scans showed at SPECT/CT 16 neck lymph node (LN) metastases, three unclear and 13 occult at WBS. Significant involvement of some tissue risk factors with metastasis appearance was observed, such as minimal extrathyroid tumor extension and neck LN metastases. These risk factors should be carefully considered in DTC patient follow-up where ¹³¹I-SPECT/CT routinely use is suggested as a support tool of WBS.

Clinical applications of single-photon emission computed tomography/computed tomography in post-ablation 131iodine scintigraphy in children and young adults with differentiated thyroid carcinoma

BACKGROUND

The utility of integrated single-photon emission computed tomography/computed tomography (SPECT/CT) in children and young adults with differentiated thyroid carcinoma is incompletely studied.

OBJECTIVE

To determine the value of adding SPECT/CT to conventional whole-body scintigraphy in post-ablation iodine-131 (¹³¹I) scintigraphy for children and young adults with differentiated thyroid carcinoma.

MATERIALS AND METHODS

Planar scintigraphy and SPECT/CT were performed on 42 post-surgical children and young adults (32 female, 10 male; mean age 14.3±4.9 years, range 7-20 years) with differentiated thyroid carcinoma (39 papillary, 2 follicular, 1 mixed) 5 days after the therapeutic administration of 1.9-7.4 GBq of ¹³¹I. Planar and SPECT/CT images were interpreted independently, and sites of uptake were categorized as positive or equivocal with respect to thyroid bed, lymph node and distant metastasis uptake. An experienced thyroid endocrinologist used a combination of surgical histopathology and scintigraphic findings to determine whether the addition of SPECT/CT would change patient management.

RESULTS

Planar scintigraphy evidenced 88 radioiodine-avid foci and SPECT/CT confirmed all foci. No additional foci were disclosed by SPECT/CT. SPECT/CT correctly classified 16/88 (18%) foci that were unclear or wrongly classified at planar scintigraphy. Globally, SPECT/CT showed an incremental value over planar scintigraphy in 9 (21.4%) patients and changed therapeutic management in 3 (7.1%; 95% confidence interval, 2-20%) patients.

CONCLUSION

SPECT/CT improved localization and characterization of focal ¹³¹I uptake on post-ablation whole-body scintigraphy in children and young adults with differentiated thyroid carcinoma. Further prospective evaluation in a larger series is justified to prove the effect of post-ablation SPECT/CT-based management decisions.

Usefulness of PET/CT with 18F-FDG in Patients with Differentiated Thyroid Carcinoma after Radioiodine Therapy: An Italian Multicenter Study

Background: our aim was to assess the diagnostic performance and clinical impact of ¹⁸F-FDG PET/CT in patients with differentiated thyroid carcinoma (DTC), previously treated with surgery and radioiodine therapy (RAI). Methods: patients subjected to ¹⁸F-FDG PET/CT for suspected DTC recurrence in three Italian nuclear medicine units were evaluated. Two different clinical settings were identified: clinical setting 1 included patients (n = 40) that were enrolled according to the American Thyroid Association guidelines (i.e., negative ¹³¹1-WBS and Tg level > 10 ng/mL); and clinical setting 2, that encompassed subjects (n = 26) with serum Tg ≤ 10 ng/mL but morphological findings suspected of relapse. PET/CT’s impact was scored as significant if it provided an indication for surgery, or led to a novel therapeutic decision. Results: In total, 51/66 patients (77.3%) were ¹⁸F-FDG positive, while 15 (22.7%) were negative. PET/CT showed an overall sensitivity and specificity of 84.4% and 75%, respectively. Sensitivity was higher in clinical setting 1 (89.1%) as compared to clinical setting 2 (76.1%), although this difference was not statistically significant (p = 0.83). PET/CT influenced clinical management in 28 cases (42.4%), without a significant difference between the 2 groups of patients (p = 0.6). Conclusions: our preliminary data, although limited by the retrospective nature of the study and possible selection bias, suggest that ¹⁸F-FDG PET/CT may be utilized for the detection of DTC recurrence in different clinical settings, with a meaningful impact on clinical management.

Unexpected radioactive iodine accumulation on whole-body scan after I-131 ablation therapy for differentiated thyroid cancer

We retrospectively evaluated the frequency of unexpected accumulation of radioactive iodine on the post-therapy whole-body scan (Rx-WBS) after radioactive iodine (RAI) ablation therapy in patients with differentiated thyroid cancer (DTC). We searched our institutional database for Rx-WBSs of DTC patients who underwent RAI ablation or adjuvant therapy between 2012 and 2019. Patients with distant metastasis diagnosed by CT or PET/CT before therapy, and those had previously received RAI therapy were excluded. In total, 293 patients (201 female and 92 male, median age 54 years) were selected. Two nuclear medicine physicians interpreted the Rx-WBS images by determining the visual intensity of radioiodine uptake by the thyroid bed, cervical and mediastinal lymph nodes, lungs, and bone. Clinical features of the patients with and without the metastatic accumulation were compared by chi-square test and median test. Logistic regression analyses were performed to compare the association between the presence of metastatic accumulation and these clinical factors. Eighty-four of 293 patients (28.7%) showed metastatic accumulation. Patients with metastatic RAI accumulation showed a significantly higher frequency of pathological N1 (pN1) and serum thyroglobulin (Tg) > 1.5 ng/ml under TSH stimulation (p = 0.035 and p = 0.031, respectively). Logistic regression analysis indicated that a serum Tg > 1.5 ng/ml was significantly correlated with the presence of metastatic accumulation (odds ratio = 1.985; p = 0.033). In conclusion, Patients with Tg > 1.5 ng/ml were more likely to show metastatic accumulation. In addition, the presence of lymph node metastasis at the initial thyroid surgery was also associated with this unexpected metastatic accumulation.

Co-Delivery of 131 I and Prima-1 by Self-Assembled CD44-Targeted Nanoparticles for Anaplastic Thyroid Carcinoma Theranostics

New radionuclide-labeled targeting nanocarrier systems have generated new opportunities for tumor treatment and imaging. Nevertheless, such therapeutic strategy is clinically unfeasible on anaplastic thyroid carcinoma (ATC) patients, because of lacking suitable targets and resistance to radiation. In order to figure out a potential treatment, immuno-histochemical staining is performed in human ATC tissue species and high expression of cluster determinant 44 (CD44) is found. Therefore, a CD44-targeted delivery system is designed and constructed by self-assembly of tyrosine (Tyr)-hyaluronic acid (HA)-polyethyleneimine (PEI), which can radiolabel ^131/125 I and load a p53 mutant restoring regent, Prima-1. The ¹²⁵ I-labeled nanocomposites display an impressive tumor imaging as well as a long radiation treatment cycle. The ¹³¹ I-labeled nanoparticles show remarkable anti ATC-tumor effects in vitro and in vivo, due to radiosensitization of Prima-1 by reactivation of the p53 mutants.

Neck lymph node metastasis detection in patients with differentiated thyroid carcinoma (DTC) in long-term follow-up: a 131I-SPECT/CT study

Background

The identification of neck lymph node (LN) metastases represents a very important issue in the management of patients with differentiated thyroid carcinoma (DTC). To this purpose, in the present study, we used 131I-SPECT/CT as a diagnostic imaging procedure.

Methods

A consecutive series of 224 DTC patients with ascertained neck radioiodine-avid foci at ¹³¹I-SPECT/CT during long-term follow-up was evaluated. All patients had already undergone total thyroidectomy and radioiodine therapy and had been classified as follows: 62 at high risk (H), 64 at low risk (L) and 98 at very low risk (VL). ¹³¹I-Whole body scan (WBS) followed by SPECT/CT was performed in all cases.

Results

In the 224 patients, 449 neck iodine avid foci were ascertained at SPECT/CT, while 322 were evidenced at WBS in 165/224 patients. WBS classified as residues 263/322 foci and as unclear 59/322 foci; among the former foci SPECT/CT correctly characterized 8 LN metastases and 3 physiologic uptakes and among the latter, it pinpointed 26 LN metastases, 18 residues, and 15 physiologic uptakes. SPECT/CT also classified 127 foci occult at WBS as 59 LN metastases and 68 residues. Globally, SPECT/CT identified 93 LN metastases in 59 patients (26 H, 20 L, 13 VL), while WBS evidenced 34 in 25 cases. All 13 VL patients, T1aN0M0, 5 of whom with LN near sub-mandibular glands, had thyroglobulin undetectable or < 2.5 ng/ml. Globally, SPECT/CT obtained an incremental value than WBS in 45.5% of patients, a more correct patient classification changing therapeutic approach in 30.3% of cases and identified WBS false-positive findings in 8% of cases.

Conclusions

¹³¹I-SPECT/CT proved to correctly detect and characterize neck LN metastases in DTC patients in long-term follow-up, improving the performance of planar WBS. SPECT/CT routine use is thus suggested; its role is particularly relevant in patients with WBS inconclusive, VL, T1aN0M0 and with undetectable or very low thyroglobulin levels.

Papillary Thyroid Micro Carcinoma: The Incidence of High-Risk Features and Its Prognostic Implications

Background: The current management of papillary thyroid micro carcinoma (PTMC) has become more conservative. However, high-risk characteristics that can only be revealed post-surgically exist. Patients and clinicians need to estimate the risks and understand the prognostic meaning of these factors. Methods: We retrospectively analyzed 246 consecutive patients with PTMC who underwent surgery at our institution between 2015 and 2017. Clinical and histopathological parameters that may indicate recurrent disease were investigated. The responses to therapy in cases with different risks of recurrence were analyzed. Results: A total of 79.26% (195/246) of patients received total thyroidectomy (TT), of whom 177 (90.77%) also received central lymph node dissection. Radioiodine ablation (RAI) was applied in 64.23% (158/246) of patients. Intermediate-high risk features were identified in 27.64% (68/246) after primary treatment. After a median follow-up of 18 months (range, 6-39 months), 121 of 158 (76.58%) patients who received TT+RAI were evaluated as an excellent response. An incomplete response (IR) was observed in 14.56% (23/158) of this group of PTMC. Multivariate analysis identified extra thyroid extension (P = 0.001) and intermediate-high risk stratification (P = 0.014) as significant and independent risk factors for an IR. Conclusions: A total of 27.64% of PTMC cases evaluated as a low risk of recurrence pre-surgery showed intermediate to high risk disease post-surgery, and this leads to a higher rate of IR.