Incidental thyroid lesions detected by FDG-PET/CT: prevalence and risk of thyroid cancer

Prevalence and Significance of Incidental PET/CT Findings of Cancer Detected in Patients Evaluated for Their Primary Hematologic Malignancy: A Systematic Review

In the evaluation of a patient's primary hematologic malignancy, positron emission tomography/computed tomography (PET/CT) imaging may incidentally detect a concerning abnormality suggestive of a second concurrent cancer. Despite accounting for nearly 10% of all cancers diagnosed in Canada, there has yet to be a systematic review focused on the prevalence and significance of these incidental PET/CT findings in the context of primary hematologic malignancies. As such, a systematic search strategy was employed on MEDLINE and Embase to document the prevalence and clinical significance of incidental PET/CT findings suggestive of a second concurrent cancer detected in patients evaluated for their primary hematologic malignancy. Thirteen studies published between 2008 and 2022 were reviewed, including conference abstracts (n = 8) and journal articles (n = 5). Clinically significant incidental cancers were detected with a median of 2.4% (range: 1.1-10.3%) in patients with myeloma/plasma cell disorders, compared to a median of 1.5% (range: 0.3-2.8%) in patients with lymphoproliferative diseases. The most common anatomic regions of clinically significant incidental malignancies were identified in the gastrointestinal tract (44.4%), followed by the thyroid gland (22.2%) and lungs (7.9%). In most cases, early detection of incidental cancers led to successful early interventions. PET/CT scans occasionally identify second primary malignancies that require additional attention. These findings may affect the treatment of a patient's primary hematologic malignancy, and as such, timely coordinated management is important for improved outcomes. This review may inform physicians and administrators of the risk of incidental second malignancies and may highlight a need for enhanced cancer treatment pathways.

Complimentary Role of [18F]FDG and [18F]NaF-PET/CT in Evaluating Synchronous Thyroid Carcinoma and Parathyroid Adenoma with Brown Tumors

We herein present a patient initially suspected of multiple lytic skeletal metastasis of unknown primary on anatomical imaging. Metabolic imaging by [18F]-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) detected focal [18F]FDG uptake in the right thyroid nodule, mild [18F]FDG uptake in soft tissue lesion in the left inferior parathyroid region, and multiple nonavid osteolytic skeletal lesions. Fine-needle aspiration cytology of the right thyroid nodule showed papillary thyroid carcinoma (PTC). The patient had raised serum parathyroid hormone and serum calcium levels, suggesting parathyroid disease. [18F]-sodium fluoride (NaF)-PET/CT showed a metabolic superscan pattern of hyperparathyroidism with brown tumors rather than metastatic lytic skeletal lesions. Patient underwent total thyroidectomy and bilateral central compartment clearance, along with soft tissue lesion resection in the left inferior parathyroid region. Finally, histopathology confirmed PTC classical variant with no aggressive histology features (pT1N0) for thyroid nodule and parathyroid adenoma for soft tissue lesion in the left inferior parathyroid region. The findings of the [18F]FDG and [18F]NaF-PET/CT imaging were helpful for making a final diagnosis of synchronous thyroid cancer and parathyroid adenoma, which in turn guided the appropriate treatment strategy.

Sonographic risk stratification of FDG-avid thyroid nodules using the Thyroid Imaging Reporting and Data System

INTRODUCTION

The increasing usage of positron emission tomography/computed tomography (PET/CT) for detection and monitoring of malignancy has led to an increase in incidental detection of thyroid nodules. Nodules that demonstrate increased avidity for 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) have been shown to carry a high incidence of malignancy and warrant further investigation. At present, there has been limited research on the risk stratification of FDG-avid thyroid incidentalomas. Thus, this study aims to evaluate the efficacy of the ACR TIRADS classification in the risk stratification of such nodules.

METHODS

Data were collected retrospectively for FDG-avid thyroid incidentalomas over a 10-year period. Nodules were characterised using the TIRADS classification and, subsequently, underwent fine-needle aspirate cytology. Cytological findings were classified using the Bethesda reporting system. Non-diagnostic samples (Bethesda class I) were excluded. The remaining samples were divided into two groups: benign (Bethesda class II) or suspicious for malignancy/malignant (Bethesda class III or above).

RESULTS

Thirty-six percent of low-risk nodules and 45% of high-risk nodules were malignant, respectively (P = 0.516). The sensitivity and specificity of TIRADS for detection of malignant nodules were 56% and 54%, respectively. There were no malignant TIRADS 1 or 2 nodules. The absence of any suspicious sonographic features had a 1.0 negative predictive value.

CONCLUSIONS

FDG-avid nodules classified as TIRADS 1 or 2 or have no suspicious ultrasound features have a 0% incidence of malignancy and thus may not require further assessment with fine-needle aspirate cytology (FNA) when detected incidentally. FDG-avid nodules that are TIRADS 3 or above should undergo FNA regardless of size due to the high risk of malignancy and poor sensitivity of the TIRADS classification system.

Retrospective study of qualitative assessment in detecting synchronous and metachronous malignancies in adult cancer patients by 18 F-FDG PET/CT

OBJECTIVES

The study aimed to evaluate the frequency of incidental suspicious lesions detected by flourine-18 fluorodeoxyglucose PET/computed tomography ( 18 F-FDG PET/CT) scans done for staging or restaging in adult cancer patients. We further determined the detection rate of synchronous and metachronous malignancies in these suspicious lesions after further investigations.

MATERIALS AND METHODS

This retrospective analysis evaluated the consecutive patients with 18 F-FDG PET/CT scans done in Queen Elizabeth Hospital (QEH), Hong Kong between July 2021 and June 2022. The adult cancer patients who underwent staging or restaging 8 F-FDG PET/CT were included while the remaining were excluded. Patients' demographics, primary cancer type, tumor markers, and pathological analyses for the incidental suspicious lesions were reviewed to establish the detection rate of synchronous and metachronous malignancies.

RESULTS

A total of 2054 patients fulfilled inclusion criteria with age ranging from 18 to 93 years old. Out of the 2054 patients, 304 (14.8%) were found to have incidental suspicious lesions. Of these, 206 patients (67.8%) underwent further investigations including pathological analyses. Subsequently, 84 of these 206 patients (40.8%) had pathologically proven synchronous or metachronous malignancies.

CONCLUSION

The detection rate of incidental suspicious lesions in adult cancer patients who underwent 18 F-FDG PET/CT scans for staging or restaging was 14.8% and the rate of synchronous and metachronous malignancies in these suspicious lesions was 40.8%. The treatment plan of these patients may potentially be altered, which should be included in the cost-benefit analysis of using this imaging modality.

Incidental 68Ga-DOTATATE uptake in thyroid nodules: Is guideline-directed management still appropriate?

BACKGROUND

Fluorodeoxyglucose uptake on positron emission tomography imaging has been shown to be an independent risk factor for malignancy in thyroid nodules. More recently, a new positron emission tomography radiotracer-Gallium-68 DOTATATE-has gained popularity as a sensitive method to detect neuroendocrine tumors. With greater availability of this imaging, incidental Gallium-68 DOTATATE uptake in the thyroid gland has increased. It is unclear whether current guideline-directed management of thyroid nodules remains appropriate in those that are Gallium-68 DOTATATE avid.

METHODS

We retrospectively reviewed Gallium-68 DOTATATE positron emission tomography scans performed at our institution from 2012 to 2022. Patients with incidental focal Gallium-68 DOTATATE uptake in the thyroid gland were included. Fine needle aspiration biopsies were characterized via the Bethesda System for Reporting Thyroid Cytopathology. Bethesda III/IV nodules underwent molecular testing (ThyroSeq v3), and malignancy risk ≥50% was considered positive.

RESULTS

In total, 1,176 Gallium-68 DOTATATE PET scans were reviewed across 837 unique patients. Fifty-three (6.3%) patients demonstrated focal Gallium-68 DOTATATE thyroid uptake. Nine patients were imaged for known medullary thyroid cancer. Forty-four patients had incidental radiotracer uptake in the thyroid and were included in our study. Patients included in the study were predominantly female sex (75%), with an average age of 62.9 ± 13.9 years and a maximum standardized uptake value in the thyroid of 7.3 ± 5.3. Frequent indications for imaging included neuroendocrine tumors of the small bowel (n = 17), lung (n = 8), and pancreas (n = 7). Thirty-three patients underwent subsequent thyroid ultrasound. Sonographic findings warranted biopsy in 24 patients, of which 3 were lost to follow-up. Cytopathology and molecular testing results are as follows: 12 Bethesda II (57.1%), 6 Bethesda III/ThyroSeq-negative (28.6%), 1 Bethesda III/ThyroSeq-positive (4.8%), 2 Bethesda V/VI (9.5%). Four nodules were resected, revealing 2 papillary thyroid cancers, 1 neoplasm with papillary-like nuclear features, and 1 follicular adenoma. There was no difference in maximum standardized uptake value between benign and malignant nodules (7.0 ± 4.6 vs 13.1 ± 5.7, P = .106). Overall, the malignancy rate among patients with sonography and appropriate follow-up was 6.7% (2/30). Among patients with cyto- or histopathology, the malignancy rate was 9.5% (2/21). There were no incidental cases of medullary thyroid cancer.

CONCLUSION

The malignancy rate among thyroid nodules with incidental Gallium-68 DOTATATE uptake is comparable to rates reported among thyroid nodules in the general population. Guideline-directed management of thyroid nodules remains appropriate in those with incidental Gallium-68 DOTATATE uptake.

Prevalence and clinical significance in our setting of incidental uptake in the thyroid gland found on 18F-fluordeoxyglucose positron emission tomography-computed tomography (PET-CT)

INTRODUCTION

The expanding use of 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) has resulted in an increased frequency of incidentally discovered areas of FDG uptake within the thyroid gland. In these incidentalomas, high malignancy rates are reported. The study aimed, on the one hand, to determine the prevalence in our setting of thyroid incidentalomas in patients with no previous history of thyroid cancer undergoing an FDG PET-CT as well as the risk of malignancy and, on the other hand, to evaluate the usefulness of the maximum standard uptake value (SUVmax) for detecting thyroid cancer.

MATERIAL AND METHODS

The FDG PET-CT scans performed at our hospital between June 2013 and December 2020 were retrospectively reviewed. In those incidentalomas with sufficient additional investigation, a diagnosis of benign or malignant was established based on the complementary tests.

RESULTS

From the 21,594 PET-CT scans performed, 398 (1.8%) patients had an incidental FDG uptake, either focal (n=324) or diffuse (n=74). Among incidentalomas with further investigation, the rate of malignancy was higher in patients with focal FDG uptake than in those with diffuse uptake (26.5% versus 4%, respectively, p<0.05). The SUVmax value was significantly lower in benign focal lesions (5.7 [range: 2.3-66] than in malignant ones 10.6 [range: 3.1-51.2]; p<0.05). Nearly a quarter of malignant diagnoses (23.3%) were related to potentially aggressive tumours.

CONCLUSION

The high rate of malignant tumours found among PET-CT incidentalomas and the high proportion of aggressive tumours demonstrate the need for a standardised approach in the investigation of incidental focal FDG uptake in the thyroid gland.

Abnormality Pattern of F-18 FDG PET Whole Body with Functional MRI Brain in Post-Acute COVID-19

Purpose

The study aimed to investigate imaging abnormalities associated with post-acute COVID-19 using F-18 FDG PET/CT and PET/ rsfMRI brain.

Methods

We retrospectively recruited 13 patients with post-acute COVID-19. The post-acute COVID-19 symptoms and neuropsychiatric tests were performed before F-18 FDG PET/CT whole body with PET/rsfMRI brain. Qualitative and semiquantitative analyses were also conducted in both whole body and brain images.

Results

Among the 13 patients, 8 (61.5%) had myositis, followed by 8 (61.5%) with vasculitis (mainly in the thoracic aorta), and 7 (53.8%) with lung abnormalities.. Interestingly, one patient with a very high serum RBD IgG antibody demonstrated diffuse myositis throughout the body which potentially associated with immune-mediated myositis. One patient experienced psoriasis exacerbation with autoimmune-mediated after COVID-19. Most patients had multiple areas of abnormal brain connectivity involving the frontal and parieto-temporo-occipital lobes, as well as the thalamus.

Conclusion

The whole body F-18 FDG PET can be a potential tool to assess inflammatory process and support the hyperinflammatory etiology, mainly for lesions in skeletal muscle, vascular wall, and lung, as well as, multiple brain abnormalities in post-acute COVID-19. Nonetheless, further studies are recommended to confirm the results.

Active Surveillance for Papillary Thyroid Microcarcinoma in a Population with Restrictive Diagnostic Workup Strategies

Background: The worldwide incidence of papillary thyroid carcinoma (PTC) has increased. Efforts to reduce overtreatment follow two approaches: limiting diagnostic workup of low-risk thyroid nodules and pursuing active surveillance (AS) after diagnosis of microscopic PTC (mPTC). However, most studies on AS have been performed in countries with a relatively high proportion of overdiagnosis and thus incidental mPTC. The role of AS in a population with a restrictive diagnostic workup protocol for imaging and fine-needle aspiration remains unknown. Therefore, the aim of this study was to describe the proportion and characteristics of patients with mPTC in the Netherlands and to describe the potential candidates for AS in a situation with restrictive diagnostic protocols since 2007. Methods: All operated patients with an mPTC in the Netherlands between 2005 and 2015 were identified from the Netherlands Cancer Registry database. Three groups were defined: (Group 1) mPTC with preoperative distant or lymph node metastases, (Group 2) mPTC in pathology report after thyroid surgery for another indication, and (Group 3) patients with a preoperative high suspicious thyroid nodule or proven mPTC (Bethesda 5 or 6). Only patients in Group 3 were considered potential candidates for AS. Results: A total of 1018 mPTC patients were identified. Group 1 consisted of 152 patients with preoperatively discovered metastases. Group 2 consisted of 667 patients, of whom 16 (2.4%) had lymph node metastases. There were 199 patients in Group 3, of whom 27 (13.6%) had lymph node metastases. After initial treatment in Group 3, 3.5% (7/199) of the patients had recurrence. Conclusions: Restrictive diagnostic workup strategies of patients with small thyroid nodules lead to limited patients eligible for AS and a higher incidence of lymph node metastases. We believe that there is limited additive value for AS in countries with restrictive diagnostic workup guidelines such as in the Netherlands. However, if an mPTC is encountered, AS can be offered on an individual basis.

PET/CT Variants and Pitfalls in Head and Neck Cancers Including Thyroid Cancer

PET/CT imaging is a dual-modality diagnostic technology that merges metabolic and structural imaging. There are several currently available radiotracers, but ¹⁸F-FDG is the most commonly utilized due to its widespread availability. ¹⁸F-FDG PET/CT is a cornerstone of head and neck squamous cell carcinoma imaging. ⁶⁸Ga-DOTA-TOC is another widely used radiotracer. It allows for whole-body imaging of cellular somatostatin receptors, commonly expressed by neuroendocrine tumors and is the standard of reference for the characterization and staging of neuroendocrine tumors. The normal biodistribution of these PET radiotracers as well as the technical aspects of image acquisition and inadequate patient preparation affect the quality of PET/CT imaging. In addition, normal variants, artifacts and incidental findings may impede accurate image interpretation and can potentially lead to misdiagnosis. In order to correctly interpret PET/CT imaging, it is necessary to have a comprehensive knowledge of the normal anatomy of the head and neck and to be cognizant of potential imaging pitfalls. The interpreter must be familiar with benign conditions which may accumulate radiotracer potentially mimicking neoplastic processes and also be aware of malignancies which can demonstrate low radiotracer uptake. Appropriate use of structural imaging with either CT, MR or ultrasound can serve a complimentary role in several head and neck pathologies including local tumor staging, detection of bone marrow involvement or perineural spread, and classification of thyroid nodules. It is important to be aware of the role of these complementary modalities to maximize diagnostic accuracy and patient outcomes. The purpose of this article is to outline the basic principles of PET/CT imaging, with a focus on ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTA PET/CT. Basic physiology, variant imaging appearances and potential pitfalls of image interpretation are presented within the context of common use cases of PET technology in patients with head and neck cancers and other pathologies, benign and malignant.

Prevalence of incidental thyroid malignancy on routine 18F-fluorodeoxyglucose PET-CT in a large teaching hospital

Purpose

To quantify incidental thyroid pathology including malignancy on routine ¹⁸F-FDG PET-CT scans

To compare standardised uptake values (SUV_max) in thyroid malignancy subtypes

Methods and materials

This is a retrospective study of all ¹⁸F-FDG PET-CT scans (n = 6179) performed in a teaching hospital between June 2010 and May 2019. RIS database search of reports for the word “thyroid” was performed. Studies with evidence of thyroid uptake were included. Patient age and gender, primary indication for PET scan (malignant or non-malignant), thyroid result on PET (diffuse or focal tracer uptake, SUV_max), ultrasound and FNAC results were recorded.

Results

Incidental abnormal thyroid tracer uptake as a proportion of all ¹⁸F-FDG PET-CT scans was 4.37% (n = 270). Out of region patients (n = 87) whose records could not be obtained were excluded leaving a study group of n = 183. Ninety-four in this group had focal uptake, and 89 had diffuse uptake. Fifty-five patients in the focal group had undergone further investigations. Of these, 30 were thought to be benign on USS alone, and 25 patients underwent USS/FNAC. Thirteen (24%) malignancies were identified (5 papillary, 6 follicular, 1 poorly differentiated thyroid cancer, 1 metastatic malignancy). Mean SUV_max for papillary carcinoma was noted to be 8.2 g/ml, and follicular carcinoma was 12.6 g/ml.

Conclusion

Incidental abnormal thyroid ¹⁸F-FDG PET-CT uptake in PET-CT scans of 4.37% is in keeping with the known limited literature. Rather similar number of patients was noted in the focal and diffuse tracer uptake categories in the final study group. Around quarter of the focal lesions were identified to be malignant, implying focal lesions should always be further investigated.

Detection of thyroiditis on PET/CT imaging: a systematic review

PURPOSE

The incidence and clinical significance of thyroiditis detected by molecular imaging methods is a clinical challenge that is not widely investigated in the literature. The aim of this systematic review was to analyze published data about the detection of thyroiditis on PET or PET/CT using different tracers.

METHODS

A comprehensive computer literature search of the Scopus, PubMed/MEDLINE, Embase, and Cochrane library databases was conducted up to November 2019 to find relevant papers on the detection of thyroiditis by PET/CT, the metabolic appearance, and the clinical significance.

RESULTS

Twenty-six articles were selected and retrieved in full-text version. From the analyses of these studies, the following main findings have been found. Diffuse thyroid uptake of PET tracers is a relatively frequent event, ranging from 0.4 to 46.2%, and it is commonly related to benign disease. Thyroiditis is the most frequent reason for diffuse increased thyroid ¹⁸F-FDG uptake. Cases of malignant disease with a pattern of diffuse ¹⁸F-FDG thyroid uptake are less frequent. Preliminary studies show a possible role of thyroiditis detected by ¹⁸F-FDG PET/CT in evaluating treatment response and as a prognostic marker in oncological patients treated with immunotherapy. However, further studies are needed.

CONCLUSIONS

Diffuse ¹⁸F-FDG thyroid uptake is a relatively rare event commonly due to benign diseases, among which thyroiditis is the most common. The rate of neoplastic disease with diffuse ¹⁸F-FDG thyroid uptake is very low. Diffuse ¹⁸F-FDG thyroid uptake requires further investigation and clinical evaluation for the correct diagnosis. Currently, cases of diffuse thyroid uptake with non-¹⁸F-FDG radiotracer are only anecdotal.

Incidental cervical lymph node metastasis of papillary thyroid cancer in neck dissection specimens from a tongue squamous cell carcinoma patient: a case report

We report a rare case of lymph node metastasis of papillary thyroid cancer (PTC) incidentally detected in a neck dissection specimen of tongue squamous cell carcinoma (SCC). A 42-year-old Japanese woman was diagnosed with tongue SCC (T1N0M0, Stage I). Partial glossectomy with supraomohyoid neck dissection was performed under general anesthesia, and histopathological examinations revealed primary SCC of the tongue and neck metastasis of PTC in neck dissection specimens. A few months later, total thyroidectomy and left modified radical neck dissection were performed by thyroid surgeons. The histopathological diagnosis was PTC of both the thyroid glands. There was no evidence of tumor recurrence or distant metastasis at the 9-month follow-up.

Risk of Malignancy in FDG-Avid Thyroid Incidentalomas on PET/CT: A Prospective Study

BACKGROUND

Due to a substantial risk of malignancy, patients with focal FDG-avid thyroid incidentalomas (FFTIs) on PET/CT are in most of Denmark referred to Head and Neck Cancer (HNC) fast track programs. The aim of this study was to determine the risk of malignancy in FFTI managed in a HNC fast track program.

METHODS

A prospective cohort study including all patients with FFTI referred to the HNC fast track program, Odense University Hospital between September 1, 2016 and August 31, 2017. Ultrasonography (US) and fine-needle aspiration biopsy (FNAB) were intended to be done in all patients. Nodules with cytology of Bethesda 1, 3, 4, 5, or 6 were planned for surgical removal.

RESULTS

A total of 104 patients were included. All patients had US and 101 patients (97%) had FNAB. Forty-two patients had benign cytology classified as Bethesda 2. The remaining 62 patients underwent surgery except from 11 patients, mainly due to comorbidity. The overall risk of malignancy for patients with FFTI referred to our HNC fast track program was calculated to be 24% (23/95) based on patients with unequivocal cytology and/or histology. The only statistically significant US characteristic to predict malignancy was the appearance of irregular margins with a sensitivity of 47% and specificity of 96%.

CONCLUSION

The risk of malignancy of FFTIs handled in our HNC fast track program is 24%.

PET/CT and prediction of thyroid cancer in patients with follicular neoplasm or atypia

PURPOSE

To examine whether addition of ¹⁸F-fluoro-deoxy-glucose positron emission tomography/computed tomography (FDG-PET/CT) to fine needle aspiration biopsy (FNAB) would improve prediction of thyroid cancer in patients with FNAB-derived follicular neoplasm or atypia, classified according to focal, multifocal, diffuse, or no FDG uptake.

MATERIALS AND METHODS

Consecutive patients with FNAB-derived follicular neoplasm or atypia planned for surgery from September 2013 to March 2016 were prospectively included and considered for analysis. All patients underwent preoperative PET/CT and a clinical head and neck examination, including ultrasound of the neck and the thyroid gland. Patients with obvious signs of thyroid malignancy were excluded from the study. Histology of the surgical specimen was used as reference standard for statistical analysis.

RESULTS

Of the 108 patients included (85 women, median age 53.4 years), 31 (29%) had a thyroid nodule that was histologically verified as malignant. Sensitivity and specificity for PET/CT in detection of thyroid cancer was 79 and 32%, respectively, including a derived positive predictive value (PPV) of 31%, and a negative predictive value (NPV) of 79%. Univariate and multivariate analyses showed no significant increase in the risk of thyroid cancer among patients with focal or multifocal FDG uptake compared to patients with no FDG uptake.

CONCLUSION

Addition of PET/CT to FNAB did not improve prediction of thyroid cancer in patients with FNAB-derived follicular neoplasm or atypia.

Thyroid Gland 18F-FDG Uptake in Neurofibromatosis Type 1

PURPOSE

To investigate thyroid gland characteristics on ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) imaging in patients with neurofibromatosis type 1 (NF1).

SUBJECTS AND METHODS

Thyroid gland characteristics of patients with a clinical diagnosis of NF1 who underwent ¹⁸F-FDG PET/CT imaging for the first time to distinguish benign neurofibroma from malignant peripheral nerve sheath tumor (MPNST) at our institution (n = 69) were compared to PET/CT imaging of sarcoidosis (n = 25) and early stage lung cancer (T₁N₀M₀ tumors, n = 15) patients.

RESULTS

Two NF1 patients (3%) showed a diffuse ¹⁸F-FDG uptake in the thyroid gland, 2 patients (3%) had an irregular uptake, and 7 patients (10%) had a focal uptake. Among the sarcoidosis patients, 1 showed a diffuse uptake (4%) and 1 had an irregular uptake (4%). In the early stage lung cancer group, 1 patient showed a diffuse uptake (7%) and 1 had a focal uptake (7%). NF1 patients had larger mean thyroid volume and mean SUV_max compared to sarcoidosis patients but not compared to early stage lung cancer patients. Four NF1 patients were diagnosed with multinodular goiter, 2 patients were diagnosed with benign chronic lymphocytic thyroiditis, 1 patient had metastasis to the thyroid, and 1 patient had medullary thyroid cancer.

CONCLUSION

Even though NF1 patients did not show an increased risk of thyroid incidentaloma on PET/CT compared to previous studies on non-thyroid cancer patients, the incidence shows that awareness of possible thyroid disease is important.

Preoperatively undiagnosed papillary thyroid carcinoma in patients thyroidectomized for benign multinodular goiter

OBJECTIVE

Incidental thyroid cancers (ITCs) are often microcarcinomas; among them, the most frequent histotype is the papillary one. The purpose of this study was to evaluate the rate of papillary thyroid cancer (PTC) in patients thyroidectomized for benign multinodular goiter.

SUBJECT AND METHODS

We retrospectively evaluated the histological incidence of PTC in 207 consecutive patients who, in a 1-year period, underwent thyroidectomy for benign multinodular goiter. All patients came from an iodine-deficient area (Orleans, France) with three nuclear power stations located in the neighboring areas of the county town.

RESULTS

Overall, 25 thyroids (12.1%) harbored 37 PTC, of which 31 were microcarcinomas. In these 25 PTC patients, mean age was 55 ± 10 years (range 30-75), female:male ratio 20:5 (4:1). In 10 patients (40% of 25 and 4.8% of 207), PTCs were bilateral, and in 7 (2 with microPTCs) the thyroid capsule was infiltrated. These 7 patients underwent central and lateral cervical lymph node dissections, which revealed lymph node metastases in one and two cases, respectively. Radioiodine treatment was performed in 7 cases. Neither mortality nor transient and permanent nerve injuries were observed. Four (16%) transient hypocalcaemias occurred as early complications. At last follow-up visit (mean length of follow-up 17.2 ± 3.4 months), all patients were doing well and free of any clinical local recurrence or distant metastases.

CONCLUSION

With a 12% risk that multinodular goiter harbors preoperatively unsuspected PTCs, which can have already infiltrated the capsule and that can be accompanied by PTC foci contralaterally, an adequate surgical approach has to be considered.

Focal thyroid incidental uptake detected by 18F-fluorodeoxyglucose positron emission tomography

Aim: To perform a meta-analysis of published data on the prevalence and risk of malignancy of focal thyroid incidental uptake (FTIs) detected by Fluorine-18-Fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) or PET/CT. Methods: A comprehensive literature search of studies published up to and including December 2012 was performed. Pooled prevalence and malignancy risk of FTIs were calculated, including a sub-analysis for the geographic areas of origin of the studies. Results: 34 studies including 215 057 patients were selected. Pooled prevalence of FTIs was 1.92% (95% confidence interval [95%CI]: 1.87–1.99%). Overall, 1522 FTIs underwent histopathology evaluation. Pooled risk of malignancy was 36.2% (95%CI: 33.8–38.6%), without significant differences among various geographic areas. Conclusions: FTIs are observed in about 2% of 18F-FDG-PET or PET/CT scans and carry a significant risk of malignancy. Therefore, further investigation is warranted whenever FTIs are detected by 18F-FDG-PET or PET/CT.

Clinical significance of patterns of increased [18F]-FDG uptake in the thyroid gland: a pictorial review

In the diagnosis and staging of oncologic patients, [¹⁸F]-fluorodeoxyglucose positron emission tomography (FDG-PET) is well recognized as an important functional imaging modality. FDG-PET also has been used for cancer screening in healthy individuals. In general, the normal thyroid gland shows absent or low uptake on FDG-PET, which is often identified as an incidental finding on PET. Today, thyroid FDG uptake can be seen in three patterns: diffuse; focal; and diffuse-plus-focal. Diffuse thyroid uptake is mainly considered an indicator of chronic thyroiditis. Focal thyroid uptake has been associated with malignancy (range 25-50%). Diffuse-plus-focal uptake is not well recognized and might also indicate a risk of malignancy. Understanding the patterns of thyroid FDG uptake is thus important for nuclear medicine physicians or radiologists when giving recommendations to the referring physician. In this pictorial review, we show the clinical significance of different patterns of thyroid uptake on FDG-PET [PET/computed tomography (CT)], including ultrasonography (US) findings.

Evaluation of Incidental Thyroid Nodules in Cancer Patients

OBJECTIVE

Frequency of thyroid cancer in incidental thyroid nodules identified by imaging techniques in cancer patients is higher than that in the normal population. In the retrospective study, we have both investigated the incidence of thyroid cancer in incidentally identified nodules and compared the imaging techniques to determine whether there is any difference between them in detection of malign nodules.

METHODS

A total of 7319 patients who underwent thyroid fine-needle aspiration biopsy (FNAB) were included in the study. The data of 174 patients who had previously been diagnosed with a hematologic or solid malignancy prior to the FNAB procedure and had incidentally identified thyroid nodules were evaluated retrospectively.

RESULTS

Eighty-six (49.5%) of the incidental nodules were identified with ultrasonography (USG), 62 (35.6%) with positron emission tomography (PET) or PET/computed tomography (PET/CT), and 26 (14.9%) with CT. As a result of thyroidectomy, papillary carcinoma was identified in 8 (4.6%) patients, and metastasis to the thyroid of a primary cancer was found in 3 (1.7%) patients. While the papillary carcinoma proportion in the nodules identified by USG was 3.4%, PET/CT was 8.9%. A cut-off maximal standardized uptake value of 11.6 in PET/CT indicated malignancy achieving a sensitivity of 83.3% and a specificity of 91.1%.

CONCLUSION

Whether the nodule in the incidental thyroid nodules of cancer patients is identified using USG or PET/CT, the risk of thyroid cancer is similar. However, cancer risk is higher in the event of a higher focal uptake in the nodules identified by PET/CT.

Comparison of Core-Needle Biopsy and Fine-Needle Aspiration for Evaluating Thyroid Incidentalomas Detected by 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography: A Propensity Score Analysis

BACKGROUND

This study used a propensity score analysis to assess the roles of core-needle biopsy (CNB) and fine-needle aspiration (FNA) in the evaluation of thyroid incidentalomas detected on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT).

METHODS

The study population was obtained from a historical cohort who underwent ¹⁸F-FDG PET/CT between October 2008 and September 2015. Patients were included who underwent ultrasound-guided CNB or FNA for incidental focal uptake of ¹⁸F-FDG in the thyroid gland on PET/CT. The primary study outcomes included the inconclusive result rates in the CNB and FNA groups. The secondary outcome measures included the non-diagnostic result rate and the diagnostic performance for neoplasms. Multivariate analysis, propensity score matching, and inverse probability weighting were conducted.

RESULTS

A total of 1360 nodules from 1338 patients were included in this study: 859 nodules from 850 patients underwent FNA, and 501 nodules from 488 patients underwent CNB. Compared to FNA, CNB demonstrated a significantly lower inconclusive result rate in the pooled cohort (23.8% vs. 35.4%; p < 0.001), propensity score-matched cohorts (22.9% vs. 36.6%; p < 0.001), and with inverse probability weighting (22.4% vs. 35.2%; p < 0.001). Non-diagnostic result rates were also significantly lower in CNB than in FNA. The diagnostic performance of the two groups in the pooled and matched cohorts was similar, with no significant differences found.

CONCLUSIONS

The significantly lower inconclusive result rates in CNB than in FNA were consistent within the propensity score-matched cohorts. Therefore, CNB appears to be a promising diagnostic tool for patients with thyroid incidentalomas detected on ¹⁸F-FDG PET/CT.

Malignancy rate of focal thyroid incidentaloma detected by FDG PET-CT: results of a prospective cohort study

OBJECTIVE

To evaluate the malignancy rate of focal thyroid incidentaloma (fTI) in a population of patients undergoing a 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) for a non-thyroid purpose.

DESIGN

We conducted a prospective cohort study from January 2013 to November 2014. All consecutive patients referred for a FDG PET-CT were prospectively screened. Patients with known neoplastic thyroid disease were excluded from the analysis. All patients presenting one or more fTI and who accepted to benefit from a complementary thyroid ultrasonography (US) were included and managed according to the French endocrine society consensus. Prevalence of fTI in our population and malignancy rate was assessed.

RESULTS

During the inclusion period, 10,171 patients were referred for a FDG PET-CT in our center. Fifty-three patients presenting a known thyroid disease were excluded. Among the remaining 10,118 patients, 127 (1.3%) with 131 fTI were individualized. US could not be performed in 37 patients. The remaining 90 patients (92 fTI) were explored by US ± fine-needle aspiration biopsy (FNAB). US results demonstrated a nodule aspect in 80 cases of which 60 benefited from FNAB. Nineteen of 92 fTI underwent surgery with 10 malignant lesions among the 60 patients performing both US and FNAB.

CONCLUSION

The prevalence of fTI discovered on FDG PET-CT in our population was 1.3% with 10 malignant lesions among the 60 patients performing both US and FNAB.

Cytological evaluation by fine needle aspiration biopsy of incidental focal increased fluorodeoxyglucose uptake in thyroid on positron emission tomography scan

BACKGROUND

With the increased use of whole body fluorodeoxyglucose positron emission tomography (PET) scan for staging/restaging or primary diagnosis of neoplasia, thyroid incidentalomas have become more common. The limited reports of PET-positive thyroid incidentalomas showed incidence of malignancy ranging from 14 to 66%, and there is discrepancy in terms of the diagnostic significance of the standard uptake value (SUV) value.

METHODS

This is a retrospective study of 20 PET incidentalomas which had cytological evaluation from October 2009 to February 2015 at a tertiary care university medical center, M:F = 8:12.

RESULTS

Of the 20 cases, 14 (70%) had a cytological diagnosis of atypia or suspicious for neoplasia. Eleven of those (55%) underwent surgical resection with final diagnosis of PTC in 8 cases, follicular carcinoma in one case (5%), follicular adenoma in one case (5%), and Hurthle cell adenoma in one case (5%). There was good correlation between cytological and histological diagnosis. For two cases with cytological diagnosis of suspicious for follicular neoplasm, no further histological diagnosis was obtained. One patient had direct cytological diagnosis of PTC also did not undergo surgical resection/diagnosis due to the advanced primary pancreatic adenocarcinoma. The remaining 6 (30%) cases had a cytological diagnosis of benign follicular nodule. Furthermore, no significant difference between malignant SUV and benign SUV was observed.

CONCLUSIONS

Malignancy was identified in 50% of the PET-positive incidentalomas in our series. PTC constitutes the major malignant diagnosis. No diagnostic value of SUV was observed to differentiate malignant from benign lesions. Diagn. Cytopathol. 2017;45:501-506. © 2017 Wiley Periodicals, Inc.

Clinical significance of thyroid incidentalomas identified by 18F-FDG PET/CT: correlation of ultrasonograpy findings with cytology results

AIM

The aim of this study was to investigate the clinical importance of incidental focal or diffuse fluorine-18 fluorodeoxyglucose (F-FDG) uptake in the thyroid gland on positron emission tomography (PET)/computed tomography (CT) and to evaluate the additive value of thyroid ultrasonography (US) in defining the malignancy potential of thyroid incidentalomas.

PATIENTS AND METHODS

A total of 1450 patients, who had undergone a PET/CT scan for staging or restaging of various malignancies, were screened retrospectively and 52 (3.6%) patients with focal or diffuse F-FDG uptake in the thyroid gland on PET/CT were enrolled in the study. None of the patients had any history of thyroid diseases. Thyroid US with elastography for a thyroid nodule was performed for all the patients cross-sectionally. Thyroid fine-needle aspiration biopsy (FNAB) was also applied at the same time as the thyroid US to 34 patients with a nodule(s) 10 mm or more in diameter or less than 10 mm, but with malignancy potential ultrasonographically. The cytology results were compared with the thyroid US and F-FDG PET/CT findings.

RESULTS

Although 39 patients had focal (group 1) F-FDG uptake in the thyroid gland, the remaining 13 patients had diffuse (group 2) uptake. In group 1, FNAB was performed in 32 patients. In 10 of 32 (31%) patients, FNAB results were concordant with malignant cytology (seven primary thyroid malignancy and three metastasis to thyroid). In group 2, in one of two patients who had undergone FNAB, malignant cytology (metastasis to thyroid) was detected. Although the difference between the maximum standardized uptake value (SUVmax) of malignant and benign nodules was statistically significant (10.2±8.9 vs. 5.6±3.0, P=0.013), the difference between the nodule sizes was not statistically significant (20.0±7.3 vs. 16.7±7.4, P=0.923). The presence of suspicious US findings and a high elastography score (≥4) were also statistically significant (P<0.001 and P=0.035, respectively). In the receiver-operator characteristic analysis, a 5.3 cut-off SUVmax was calculated with 82% sensitivity and 65% specificity for predicting malignant cytology.

CONCLUSION

Focal F-FDG uptake was associated with a higher prevalence of malignant thyroid nodule compared with diffuse F-FDG uptake. In particular, if a focal thyroid incidentaloma with high SUVmax (>5.5), suspicious US findings, and a high elastography score (≥4) is detected, a pathological diagnosis, either by histology or by cytology examination, should be made, especially when the patient has a long life expectancy.

Survival Outcomes for Patients With Indeterminate 18FDG-PET Scan for Extrahepatic Disease Before Liver Resection for Metastatic Colorectal Cancer: A Retrospective Cohort Study Using a Prospectively Maintained Database to Analyze Survival Outcomes for Patients With Indeterminate Extrahepatic Disease on 18FDG-PET Scan Before Liver Resection for Metastatic Colorectal Cancer

OBJECTIVE

The aim of this study was to evaluate overall survival (OS) and cancer recurrence for patients with indeterminate positron emission tomography (PET) scan for extrahepatic disease (EHD) before liver resection (LR) for colorectal liver metastases (CLMs).

SUMMARY OF BACKGROUND DATA

Indeterminate EHD as determined by PET imaging indicates a probability of extrahepatic malignancy and potentially excludes patients from undergoing LR for CLM.

METHODS

In a retrospective analysis of prospectively collected data from February 2006 to December 2014, OS for patients with indeterminate EHD on FDG-PET scan before LR for CLM was performed using standard survival analysis methods, including Kaplan-Meier estimator and Cox proportional hazard models for multivariate analyses. Postoperative imaging was used as reference to evaluate the association between indeterminate EHD and recurrence.

RESULTS

Of 267 patients with PET scans before LR, 197 patients had no EHD and 70 patients had indeterminate EHD. Median follow-up was 33 months. The estimated 5-year OS was 60.8% versus 59.4% for indeterminate and absent EHD, respectively (P = 0.625). Disease-free survival was comparable between both groups (P = 0.975) and overall recurrence was 57.1% and 59.5% for indeterminate and absent EHD, respectively (P = 0.742). About 16.9% of recurrence was associated with the site of indeterminate EHD, with 80% of associated recurrence occurring in the thorax.

CONCLUSIONS

The site of indeterminate EHD appears to have a predictive value for recurrence, with indeterminate EHD in the thorax having a higher probability of malignancy. The evidence in this report supports the critical evaluation of PET scan results and that patients are not denied potential curative LR unless the evidence for unresectable EHD is certain.

Should the Prevalence of Incidental Thyroid Cancer Determine the Extent of Surgery in Multinodular Goiter?

Background

The most appropriate surgical procedure for multinodular goiter (MNG) remains under debate. Incidental thyroid carcinoma (ITC) is often identified on histopathological examination after thyroidectomy performed for presumed benign MNG.

Aim of the study

The aim of the study was to determine the value of radical surgery for MNG patients considering the prevalence of ITC diagnosed postoperatively.

Materials and Methods

We conducted retrospective analysis of the medical records of 2,306 patients surgically treated for MNG between 2008 and 2013 at one center. None of the patients presented with any suspicion of malignancy, history of familial thyroid cancer, multiple endocrine neoplasia syndrome or previous head or neck radiation exposure.

Results

Among the 2,306 MNG patients, ITC was detected in 49 (2.12%) (44 women and 5 men, with average ages of 52.2 (21–79) and 55.6 (52–62), respectively). Papillary thyroid carcinoma was significantly more frequently observed than other types of ITC (p<0.00001). Among the MNG patients, 866 (37.5%) underwent total/near total surgery, 464 (20.1%) received subtotal thyroidectomy, and 701 (30.3%) received the Dunhill operation. The remaining 275 (11.9%) patients underwent a less radical procedure and were classified as "others." Among the 49 (100%) patients with ITC, 28 (57.1%) underwent radical surgery. Another 21 (42.9%) patients required completion surgery due to an insufficient primary surgical procedure. A total of 21 (2.42%) patients in the total/near total surgery group were diagnosed with ITC, as well as 16 (2.48%) in the subtotal thyroidectomy group and 12 (1.71%) in the Dunhill operation group; 21 (100%), 4 (25%) and 3 (25%) of these patients, respectively, underwent radical surgery; thus, 0 (0%), 12 (75%) and 9 (75%) required completion surgery. The prevalence rates of ITC were comparable between the radical and subtotal surgery groups (2.42% and 3.44%, respectively, p = 0.4046), and the prevalence was higher in the radical surgery group than in the Dunhill operation group (2.42% and 1.71%, respectively, p = 0.0873). A significant difference was observed between the group of patients who underwent total/near total surgery, among whom all of the patients with ITC (100%) received primary radical surgery, and the groups of patients who received the subtotal and Dunhill operations, among whom only 25% of the patients with ITC in each group received primary radical surgery (p<0.0001).

Conclusions

More radical procedures for MNG result in a lower risk of reoperation for ITC. The prevalence of ITC on postoperative histopathological examination should determine the extent of surgery in MNG patients. In the future, total/near total thyroidectomy should be considered for MNG patients due to the increased prevalence of ITC to avoid the necessity for reoperation.

Implication of 18F-fluorodeoxyglucose uptake by affected lymph nodes in cases with differentiated thyroid cancer

In this study, we evaluated the usefulness of positron emission tomography using ¹⁸F-fluorodeoxyglucose (FDG-PET) to detect metastatic lymph nodes in differentiated thyroid cancer. We also investigated whether certain factors, including the size of the metastasis to the lymph nodes, are associated with FDG avidity. A total of 22 consecutive patients with differentiated thyroid cancer who underwent FDG-PET preoperatively were enrolled in this study. Lymph node metastasis was diagnosed in the final pathology in 10 of the 22 patients (45.5%). The mean maximum standardized uptake value of the metastatic lymph nodes was 4.53 (range, 0-23.5). The 22 cases with differentiated thyroid cancer were divided into two groups based on lymph node metastasis. Clinicopathological variables other than FDG uptake of metastatic lymph nodes were not predictors of lymph node metastasis of thyroid cancer. The sensitivity, specificity, overall accuracy and false-negative rates of preoperative FDG-PET in the prediction of lymph node status were 40.0, 100, 72.7 and 60.0%, respectively. The false-positive rate of FDG-PET evaluation was 0%. The mean largest dimension of metastasis was 23.0 mm for FDG-positive cases and 10.9 mm for FDG-negative cases. There was a marked difference in the size of metastases between FDG-positive and -negative cases; however, even in patients with node metastasis >10 mm, the false-negative rate was 50.0%. Therefore, FDG-PET imaging was not found to be sufficient for the evaluation of lymph node status, particularly in cases with small metastases. Our findings indicate that preoperative FDG-PET evaluation of the lymph nodes cannot be considered predictive of the final pathology.

Retrospektive Analyse von Zufallsbefunden, die bei Patienten mit kutanem malignen Malignom durch (18) F-Fluordeoxyglucose-PET/CT erhoben wurden

HINTERGRUND UND ZIELE

Bei der (18) F-Fluordeoxyglucose-Positronenemissionstomographie/Computertomographie (FDG-PET/CT) ergeben sich häufig Zufallsbefunde. In der vorliegenden Studie konzentrierten wir uns auf mittels FDG-PET/CT erhaltene Zufallsbefunde bei Patienten mit kutanem Melanom und überprüften deren Relevanz hinsichtlich weiterer diagnostischer Maßnahmen und Interventionen.

PATIENTEN UND METHODEN

Die Krankenakten von 181 konsekutiven Melanom-Patienten wurden retrospektiv ausgewertet, um das Management von Zufallsbefunden zu dokumentieren. Der Schwerpunkt lag dabei auf den histologischen Befunden.

ERGEBNISSE

Bei 33 von 181 (18 %) Patienten lagen 39 relevante Zufallsbefunde vor, und zwar im Kolorektalbereich (n = 15 Patienten), in der Schilddrüse (n = 8), der Prostata (n = 2), dem Bewegungsapparat (n = 2), in Lymphknoten (n = 2), der Parotis (n = 1), den Mandeln (n = 1), den Nieren (n = 1) und der Gallenblase (n = 1). Bei 25 Patienten schlossen sich weitere diagnostische Verfahren an, wobei in 21 Fällen ein klinisches Korrelat nachgewiesen wurde. Bei 16 von 21 Patienten ergab sich eine Neoplasie, darunter fünf maligne Läsionen (vier Kolonkarzinome und ein Prostatakarzinom). Die Malignome wurden frühzeitig diagnostiziert und in der Mehrzahl der Fälle erfolgreich entfernt.

SCHLUSSFOLGERUNGEN

Der Einsatz der FDG-PET/CT als Routine-Diagnostik wird in den Leitlinien empfohlen und ist indiziert bei malignem Melanom ab Stadium IIC. In dieser Studie wurden auf effektive Weise ansonsten nicht erkannte Krebserkrankungen, insbesondere Kolonkarzinome, detektiert. In den meisten Fällen war eine frühe Intervention möglich. Zufallsbefunde durch FDG-PET/CT sollten, unter Berücksichtigung des Zustands und der Wünsche des Patienten, mit den geeigneten diagnostischen Maßnahmen abgeklärt werden.

18F-FDG PET Detection of a Medullary Thyroid Carcinoma in a Patient With SMZL

Incidental thyroid FDG uptake is not rarely encountered on PET studies. In this case, we present an incidental thyroid focus of F-FDG uptake identified in a patient with splenic marginal zone lymphoma during the baseline and the response assessment PET/CT study that proved to be medullary thyroid carcinoma on subsequent histological examination.

Thyroid Nodules Detected by Contrast-Enhanced Magnetic Resonance Angiography: Prevalence and Clinical Significance

Background and Purpose

Incidental thyroid lesions are frequently found on contrast-enhanced magnetic resonance (CE-MR) angiography. The purpose of this study is to determine the prevalence of thyroid incidentalomas detected by CE-MR angiography and to evaluate their clinical significance by correlation with ultrasound (US) and cytopathological results.

Materials and Methods

We retrospectively reviewed 3,299 consecutive CE-MR angiography examinations performed at our institution between January 2010 and March 2013. Two radiologists evaluated the CE-MR angiography imaging in consensus regarding the presence, location, and vascularity of thyroid incidentaloma. We correlated these findings with follow-up US and cytopathologic results.

Results

The prevalence of thyroid incidentalomas detected by CE-MR angiography was 4.6% (152/3,299 patients). CE-MR angiography showed hypervascularity in 86.8% (145/167), isovascularity in 8.4% (14/167), and hypovascularity in 4.8% (8/167) of thyroid nodules compared to vascularity of thyroid parenchyma. Among the patients with thyroid incidentaloma, 34 patients (22.4%) were followed by US examination, and all 36 nodules on CE-MR angiography were detected on follow-up US. Of these nodules, 9 (25%) nodules were classified as probably benign, 26 (72.2%) as indeterminate, and 1 (2.8%) as suspicious malignant nodule. Among the 16 nodules with available cytopathologic results, 12 nodules were benign, 2 nodules were follicular neoplasm, and 2 nodules showed non-diagnostic results.

Conclusion

Incidental thyroid nodules were found in 4.6% of CE-MR angiography examinations. Because the high incidence of indeterminate US feature among thyroid incidentaloma, when a thyroid incidentaloma is detected on CE-MR angiography, further evaluation with US should be performed.

THYROID MALIGNANCY RISK OF INCIDENTAL THYROID NODULES IN PATIENTS WITH NON-THYROID CANCER

Context

Thyroid incidentaloma is a common disorder in endocrinology practice. Current literature regarding the risk of thyroid cancer in incidentalomas found in patients with non-thyroid cancer is limited.

Objective

The aim of the present study was to investigate the frequency of thyroid malignancy in thyroid incidentalomas detected in patients with non-thyroid cancer.

Design

Case control study.

Subjects and Methods

The database of 287 thyroid nodules from 161 patients with a history of non-thyroid cancer followed between 2008 and 2014 were retrospectively evaluated.

Results

From 287 thyroid nodules, 69.7 % had a benign final cytology. Thyroid cancer detected in one nodule while follicular neoplasia detected in 4 nodules, atypia of unknown significance (AUS) detected in 10 nodules, Hurthle cell neoplasia detected in 5 nodules and suspicious for malignancy detected in 6 nodules according to fine needle aspiration biopsy results. Metastasis of the non-thyroid cancer to the thyroid gland was detected in 4 nodules. Twenty seven nodules from 15 patients were removed with surgery. There were 3 malignant nodules found after surgery (1 papillary, 1 follicular and 1 medullary cancer). In addition to these three thyroid cancers, two patients with benign nodules had co-incidental thyroid cancer detected after surgery. Finally, 11.1 % of thyroid nodules which underwent thyroid surgery had malignant histopathology except for co-incidental and metastatic cancers.

Conclusions

The frequency of thyroid malignancy seems not to be substantially increased in incidental thyroid nodules detected in patients with non-thyroid cancer when these patients were evaluated in nodule-based approach.

Analysis of pattern of occurrence of thyroid carcinoma between 2001 and 2010

INTRODUCTION

An ongoing discussion is found in medical literature about the reasons for changes in thyroid carcinoma incidence patterns over the last decades.

OBJECTIVE

To analyze the clinical and pathological characteristics of thyroid carcinoma cases over a decade.

METHODS

Cross-sectional study over an historical cohort. Medical records of 628 thyroid cancer cases in a single center were reviewed. 597 patients were included. Microcarcinoma cases were selected for a qualitative analysis phase, in which medical records were reviewed for better understanding of thyroid nodule and thyroid cancer diagnosis process.

RESULTS

An increase in the proportion of cases with thyroid cancer diagnosis was observed throughout the decade; new cases were predominantly tumors of less than 2 cm, with histopathological signs of low aggressiveness. There was an increase in proportion of cases with malignant cytological results among microcarcinomas.

CONCLUSION

There is a trend for increase in thyroidectomies due to cancer in this institution, with proportional increment of cases with histopathological characteristics indicative of early disease. Among microcarcinomas, there is an increasing group represented by cancer cases that were not incidentally diagnosed, related to an enhancement in preoperative diagnostic methods.

Incidence and Significance of Incidental Focal Thyroid Uptake on (18)F-FDG PET Study in a Large Patient Cohort: Retrospective Single-Centre Experience in the United Kingdom

OBJECTIVE

To assess the prevalence and pathological nature of incidental focal thyroid uptake on (18)F-FDG (2-[(18)F]-fluoro-2-deoxy-D-glucose) PET (positron emission tomography) and examine the role of the maximum standardised uptake value (SUVmax) to differentiate benign from malignant thyroid pathology.

MATERIAL AND METHODS

(18)F-FDG PET reports were retrospectively reviewed. Incidental focal tracer uptake in the thyroid was noted in 147 patients (0.5%). Patients with known primary thyroid malignancy were excluded. The final diagnosis was made following ultrasonography of the neck, fine-needle aspiration cytology (FNAC) or histopathology of the surgically resected specimen where surgery was indicated. A Mann-Whitney U test was used to compare the SUVmax of benign and malignant thyroid pathology. Receiver operating characteristic (ROC) analysis was performed to identify an SUVmax cutoff in differentiating benign from malignant pathology.

RESULTS

A final diagnosis was achieved in 47/147 (32%) of the patients. The diagnoses included benign lesions in 36 patients and malignancy in 9 patients. In 2 patients, FNAC demonstrated indeterminate follicular lesions; however, surgical excision was not performed. There was a highly significant difference in the mean SUVmax of malignant focal thyroid uptake (15.7 ± 5.9) compared to that of benign lesions (7.1 ± 6.8) with a p value of 0.000123. An SUVmax of 9.1 achieved a sensitivity of 81.6%, specificity of 100% and area under the curve of 0.915 in the ROC analysis differentiating benign from malignant disease.

CONCLUSION

The malignancy potential of incidental focal thyroid uptake remains high and warrants prompt and appropriate follow-up by the clinician. The SUVmax may aid in further characterisation of the lesion and its management.

Does the intensity of diffuse thyroid gland uptake on F-18 fluorodeoxyglucose positron emission tomography/computed tomography scan predict the severity of hypothyroidism? Correlation between maximal standardized uptake value and serum thyroid stimulating hormone levels

Context:

F-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) scan and hypothyroidism.

Aims:

The aim was to determine whether the intensity of diffuse thyroid gland uptake on F-18 FDG PET/CT scans predicts the severity of hypothyroidism.

Materials and Methods:

A retrospective analysis of 3868 patients who underwent F-18 FDG PET/CT scans, between October 2012 and June 2013 in our institution for various oncological indications was done. Out of them, 106 (2.7%) patients (79 females, 27 males) presented with bilateral diffuse thyroid gland uptake as an incidental finding. These patients were investigated retrospectively and various parameters such as age, sex, primary cancer site, maximal standardized uptake value (SUVmax), results of thyroid function tests (TFTs) and fine-needle aspiration cytology results were noted. The SUVmax values were correlated with serum thyroid stimulating hormone (S. TSH) levels using Pearson's correlation analysis.

Statistical Analysis Used:

Pearson's correlation analysis.

Results:

Clinical information and TFT (serum FT3, FT4 and TSH levels) results were available for 31 of the 106 patients (27 females, 4 males; mean age 51.5 years). Twenty-six out of 31 patients (84%) were having abnormal TFTs with abnormal TSH levels in 24/31 patients (mean S. TSH: 22.35 μIU/ml, median: 7.37 μIU/ml, range: 0.074-211 μIU/ml). Among 7 patients with normal TSH levels, 2 patients demonstrated low FT3 and FT4 levels. No significant correlation was found between maximum standardized uptake value and TSH levels (r = 0.115, P > 0.05).

Conclusions:

Incidentally detected diffuse thyroid gland uptake on F-18 FDG PET/CT scan was usually associated with hypothyroidism probably caused by autoimmune thyroiditis. Patients should be investigated promptly irrespective of the intensity of FDG uptake with TFTs to initiate replacement therapy and a USG examination to look for any suspicious nodules.

Diagnosis of incidental thyroid nodules on 18F-fluorodeoxyglucose positron emission tomography imaging: are these significant?

OBJECTIVE

To determine the prevalence of thyroid malignancy in the first UK case series of patients with incidentally detected thyroid lesions on 18F-fluorodeoxyglucose positron emission tomography imaging.

METHODS

A total of 235 patients were evaluated with 18F-fluorodeoxyglucose positron emission tomography imaging. Incidental focal uptake in the thyroid gland was identified in nine patients (3.8 per cent). A retrospective review of their case notes was conducted.

RESULTS

The rate of malignancy was 55 per cent. The mean and standard deviation of the maximum standardised uptake value was 13.1 ± 7.3 in those patients with malignancy and a nodule identified as positive on positron emission tomography. This value was 2.8 ± 1.2 in those patients without malignancy but with a nodule identified as positive on positron emission tomography (p = 0.01). A palpable thyroid nodule was more likely in those with malignant lesions (p = 0.14).

CONCLUSION

The prevalence of incidental thyroid lesions found on 18F-fluorodeoxyglucose positron emission tomography in patients with other primary malignancies is low, but the incidence of malignancy in these patients is high. Patients with a palpable thyroid nodule, focal uptake on 18F-fluorodeoxyglucose positron emission tomography and an increased maximum standardised uptake value require further investigation.

The usefulness of standardized uptake value in differentiation between benign and malignant thyroid lesions detected incidentally in 18F-FDG PET/CT examination

Introduction

In the last decade, (18)F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET and PET/CT) has become one of the major diagnostic tools used in oncology. A significant number of patients who undergo this procedure, due to non-thyroidal reasons, present incidental uptake of (¹⁸F-FDG) in the thyroid. The aim of the study was to compare the SUV_max (standardized uptake value) of thyroid focal lesions, which were incidentally found on PET/CT, in relation to the results of thyroid fine-needle aspiration biopsy (FNAB) and/or histopathological evaluation.

Materials and Methods

Patients referred for PET/CT examination, due to non-thyroidal illness, presented focal ¹⁸F-FDG uptake in the thyroid and were advised to undergo ultrasonography (US), hormonal evaluation, FNAB and/or total thyroidectomy at our institution.

Results

6614 PET/CT examinations performed in 5520 patients were analyzed. Of the 122 patients with focal thyroid ¹⁸F-FDG activity, 82 patients (67.2%) underwent further thyroid evaluation using FNAB. Benign lesions were diagnosed in 46 patients, malignant - in 19 patients (confirmed by post-surgical histopathology), while 17 patients had inconclusive results of cytological assessment. Mean SUV_max of benign lesions was 3.2±2.8 (median = 2.4), while the mean SUV_max value for malignant lesions was 7.1±8.2 (median = 3.5). The risk of malignancy was 16.7% for lesions with a SUV_max under 3, 43.8% for lesions with a SUV_max between 3 and 6, and 54.6% for lesions with a SUV_max over 6. In the group of malignant lesions, a positive correlation between the lesion’s diameter and SUV_max was observed (p = 0.03, r = 0.57).

Conclusions

Subjects with incidental focal uptake of ¹⁸F-FDG in thyroid are at a high risk of thyroid malignancy. A high value of SUV_max further increases the risk of malignancy, indicating the necessity for further cytological or histological evaluation. However, as SUV_max correlated with the diameter of malignant lesions, small lesions with focal uptake of ¹⁸F-FDG should be interpreted cautiously.

Thyroid Carcinoma Detected by 18F-Fluorodeoxyglucose Positron Emission Tomography Among Individuals Without Prior Evidence of Thyroid Disease: Relevance and Clinicopathologic Features

OBJECTIVE

The expanding use of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) has contributed to an increasing number of thyroid incidentalomas. The present study aimed to estimate the prevalence of 18F-FDG-PET thyroid incidentalomas and evaluate the clinicopathologic features of thyroid malignancies detected by 18F-FDG-PET.

METHODS

We reviewed all 18F-FDG-PET exams performed at the Portuguese Institute of Oncology, Lisbon, between 2007 and 2012 (n = 9,374). The inclusion criteria were focal thyroid uptake and absence of known thyroid disease.

RESULTS

Focal thyroid uptake was observed in 60 out of 9,374 18F-FDG-PET exams (prevalence of 0.64%). Fine-needle aspiration cytology (FNAC) was performed in 23 patients and reported as malignant in 14 cases (56.5% primary thyroid carcinoma; 4.3% secondary malignancy), as benign in 7 cases (30.5%) and as follicular lesion of undetermined significance in 2 cases (8.7%). Fourteen patients had surgery. A final histologic diagnosis of papillary thyroid carcinoma was established in 12 cases (52.2%). Three were multifocal (25.0%); 8 had extrathyroidal extension (66.7%); 5 had angioinvasion (41.7%); 3 had lymph nodes metastases (25.0%) and 2 showed lung metastases (16.7%). Overall, 91.7% were classified as intermediate or high risk. All patients had radioiodine therapy. At the last observation (mean follow-up was 29.9 months), persistent or recurrent disease was identified in 4 patients (33.3%) and none died from thyroid malignancy.

CONCLUSIONS

Thyroid carcinomas disclosed by 18F-FDG-PET are associated with aggressive histological criteria likely to carry a worse prognosis.

Unfolding the role of PET FDG scan in the management of thyroid incidentaloma in cancer patients

Thyroid incidentaloma detected on FDG-PET scan has been reported repeatedly in the last several years, though conflicting data are reported. Our aim is to identify the incidence and outcome of incidental FDG-PET detected thyroid lesions in patients undergoing FDG-PET scan for other primary malignancies and to suggest a management algorithm. This is a retrospective review of all patients who had a FDG-PET detected incidental thyroid lesion between January 2002 and December 2009 at Peter MacCallum Cancer Center. Demographics, data relating to PET scan findings, FNA diagnoses, operative details, and histopathology were reviewed. Of the 1,034 subjects who underwent the FDG-PET study, 51 (4.9%) were identified as having thyroid incidentaloma, 31 females and 20 males with a mean age of 60 years. Thyroid malignancy was noted in 39.5% (19/48 patients) who underwent FNAB. Sixteen underwent thyroidectomy. The histopathology revealed 12 patients with papillary carcinoma, 5 with follicular carcinoma and 2 with medullary carcinoma. The high rates are in concordance with analysis of the rates published in the literature. In patients with thyroid PET incidentaloma, the incidence of primary thyroid malignancy is very high as reported in our study and based on analysis of published data, necessitating further investigation. If assessment of these incidentalomas suggests malignancy, then appropriate surgical management may be warranted according to the patient's medical condition.