Thyroid incidentalomas discovered on positron emission tomography CT scanning - Malignancy rate and significance of standardised uptake values

Characteristics of malignant thyroid lesions on [18F] fluorodeoxyglucose (FDG)-Positron emission tomography (PET)/Computed tomography (CT)

Objectives

To determine the imaging variables that can best differentiate malignant from benign thyroid lesions incidentally found on F-18 FDG PET/CT scans.

Methods

All F-18 FDG PET/CT studies starting from 2011 to end of 2016 were reviewed for incidental thyroid lesions or metabolic abnormalities. Only patients who were found to have FNAB or histopathology were included. Patients with known thyroid malignancy were excluded. Patients were analyzed for age, sex, SUVmax, non-enhanced CT tissue density in mean Hounsfield units (HU), uptake pattern (focal or diffuse) and gland morphology (MNG or diffuse). A control group of 15 patients with normal thyroid glands were used to assess the tissue density in HU for normal thyroid tissue. Sensitivity, specificity, PPV, NPV and accuracy to detect malignancy were calculated. Pearson Chi-square test was used to compare categorical variables while unpaired T-test and one way ANOVA test were used to compare means of continuous variables. ROC analysis was used to assess the best cut off points for SUVmax and HU. Regression analysis was used to detect the independent predictors for malignant lesions.

Results

Biopsy was unsatisfactory or indeterminate in 4/48 patients (8%). Only 44 patients (mean age 55.2 ± 14.7; 30 females (68 %)) with unequivocal FNAB or histopathology were included for further analysis. MNG was noted in 17/44 patients (38.6 %). Thyroid malignancy was found in 16/44 (36.4 %), benign thyroid lesions in 28/44 (63.6 %). Thyroid malignancies were 12 papillary, 1 follicular, 1 Hurthle cell neoplasm and 2 lymphoma. Benign lesions were 23 benign follicular or colloid nodules and 5 autoimmune thyroiditis. Focal FDG uptake pattern was more frequently associated with malignant lesions compared to benign lesions (75 % vs. 43 %; p = 0.039). The mean SUVmax and tissue density (HU) were both higher in malignant than benign lesions (8.8 ± 8.3 vs. 3.6 ± 1.9, p = 0.024) and (48.9 ± 12.7 vs. 32.9 ± 17.5, p = 0.003) respectively. The mean HU in the control group with normal thyroid tissue was 90 ± 7.4 significantly higher than in both the benign and malignant lesions (p < 0.001). ROC analysis revealed SUVmax cutoff of >4.7 and HU cutoff of >42 to best differentiate malignant from benign lesions. The sensitivity, specificity, PPV, NPV and accuracy to detect malignancy for SUVmax>4.7 were 68.8 %, 78.6 %, 64.8 %, 81.5 & 75.0 % (p = 0.002), for HU > 42 were 81.3.0 %, 75.0 %, 65.0 %, 87.5 & 77.3 % (p = 0.0003) and for both parameters combined were 87.5 %, 60.7 %, 56.0 %, 89.5 % and accuracy of 70.5 % (p = 0.002) respectively. Only HU > 42 and SUVmax>4.7 were independent predictors for malignancy with odd ratios 8.98 and 4.93 respectively.

Conclusion

A higher tissue density (HU > 42) and SUVmax>4.7 as well as tendency for focal uptake pattern are the most significant characteristics associated with malignant thyroid lesions occasionally detected on PET/CT.

Focal Thyroid Incidentalomas on 18F-FDG PET/CT: A Systematic Review and Meta-Analysis on Prevalence, Risk of Malignancy and Inconclusive Fine Needle Aspiration

BACKGROUND

The rising demand for ¹⁸F-fluorodeoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) has led to an increase of thyroid incidentalomas. Current guidelines are restricted in giving options to tailor diagnostics and to suit the individual patient.

OBJECTIVES

We aimed at exploring the extent of potential overdiagnostics by performing a systematic review and meta-analysis of the literature on the prevalence, the risk of malignancy (ROM) and the risk of inconclusive FNAC (ROIF) of focal thyroid incidentalomas (FTI) on ¹⁸F-FDG PET/CT.

DATA SOURCES

A literature search in MEDLINE, Embase and Web of Science was performed to identify relevant studies.

STUDY SELECTION

Studies providing information on the prevalence and/or ROM of FTI on ¹⁸F-FDG PET/CT in patients with no prior history of thyroid disease were selected by two authors independently. Sixty-one studies met the inclusion criteria.

DATA ANALYSIS

A random effects meta-analysis on prevalence, ROM and ROIF with 95% confidence intervals (CIs) was performed. Heterogeneity and publication bias were tested. Risk of bias was assessed using the quality assessment of diagnostic accuracy studies (QUADAS-2) tool.

DATA SYNTHESIS

Fifty studies were suitable for prevalence analysis. In total, 12,943 FTI were identified in 640,616 patients. The pooled prevalence was 2.22% (95% CI = 1.90% - 2.54%, I² = 99%). 5151 FTI had cyto- or histopathology results available. The pooled ROM was 30.8% (95% CI = 28.1% - 33.4%, I² = 57%). 1308 (83%) of malignant nodules were papillary thyroid carcinoma (PTC). The pooled ROIF was 20.8% (95% CI = 13.7% - 27.9%, I² = 92%).

LIMITATIONS

The main limitations were the low to moderate methodological quality of the studies and the moderate to high heterogeneity of the results.

CONCLUSION

FTI are a common finding on ¹⁸F-FDG PET/CTs. Nodules are malignant in approximately one third of the cases, with the majority being PTC. Cytology results are non-diagnostic or indeterminate in one fifth of FNACs. These findings reveal the potential risk of overdiagnostics of FTI and emphasize that the workup of FTI should be performed within the context of the patient's disease and that guidelines should adopt this patient tailored approach.

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.

Positron emission tomography-computed tomography-associated incidental neoplasms of the thyroid gland

With the increasing use of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography–computed tomography (PET-CT) scans in oncology, the finding of thyroid incidentalomas, also popularly described as PET-associated incidental neoplasms (PAINs) of the thyroid gland is not unusual. The ¹⁸F-FDG PET-CT scans of all patients who underwent imaging for indications other than thyroid malignancy at our tertiary care center between January 1 and December 31, 2017, were retrospectively reviewed for PAINs of the thyroid. A total of 1737 ¹⁸F-FDG PET-CT scans were done at our center in the year 2017. 288 thyroid incidentalomas were detected in the said period; the rate of PET-CT-detected thyroid incidentalomas being 16.58%, focal incidentalomas among them being 11.7%. Only 29 out of 204 patients (14.21%) with focal thyroid incidentalomas in our cohort underwent an aspiration cytology and/or ultrasound. The rate of malignancy among the PET detected focal thyroid incidentalomas in the cohort of patients with a proven diagnosis was 10.34%. Our study highlights the challenges in the evaluation and management of PAIN in a tertiary care oncology setting. None of the factors studied including nodule size and standardized uptake value predicted the risk of malignancy. Clinicians specializing in the management of thyroid nodules need to understand the clinical significance of the PAIN, and we hope that our unique experience adds to the limited clinical information available in this regard.

Hounsfield unit value has null effect on thyroid nodules at 18F-FDG PET/CT scans

OBJECTIVES

Detection rate of thyroid nodules is increasing with the use of new imaging modalities, especially in screening for malignancies. Positron emission tomography/computed tomography (PET/ CT)-positive thyroid nodules should be differentiated for malignancy to avoid unnecessary operations and further follow-up. Most trials evaluate the role of SUVmax, but there is no definitive information about the utility of Hounsfield unit (HU) values for prediction of malignancy. This study aimed to evaluate the HU values beside SUVmax for detecting malignancy risk of PET/CT-positive thyroid nodules.

SUBJECTS AND METHODS

Results of 98 cancer patients who had fine needle aspiration biopsy (FNAB) for thyroid nodules detected on PET/CT between January 2011 and December 2015 were assessed. The FNABs and surgical pathological results were recorded.

RESULTS

FNABs revealed benign results in 32 patients (32.7%), malignant in 18 (18.4%), non-diagnostic in 20 (20.4%), and indeterminate in 28 (28.5%). Twenty-four patients underwent thyroidectomy. The mean HU values were not significantly different in benign and malignant nodules (p = 0.73). However, the mean SUVmax was significantly higher (p < 0.001) in malignant ones. Area under curve (AUC) was 0.824 for SUVmax; the cut-off value was over 5.55 (p < 0.001), with 80% sensitivity, 84.5% specificity.

CONCLUSIONS

Our current study demonstrated that HU value does not add any additional valuable information for discriminating between malignant and benign thyroid nodules. We also defined a SUV cut-off value of 5.55 for malignant potential of thyroid nodules detected on PET/CT Arch Endocrinol Metab. 2018;62(4):460-5.

The Frequency of Focal Thyroid Incidental Findings and Risk of Malignancy Detected by 18F-Fluorodeoxyglucose Positron Emission Tomography in an Iodine Deficient Population

Incidental focal uptake of 18F-fluorodeoxyglucose (FDG) in the thyroid on positron emission tomography (PET/CT) is rare but often associated with malignancy. The epidemiology of thyroid incidentalomas has only to some extent been described in countries with iodine deficiency. Here we report data from Denmark, a country with known iodine deficiency and wide access to PET/CT. All FDG PET/CT comprising the head and neck region, during 2014, were retrospectively reviewed, and patients with focal FDG uptake in the thyroid gland were identified. A total of 2451 patients had an FDG PET/CT of which 59 (2.4%) patients presented with FDG-avid focal lesions in the thyroid gland. Among the 59 patients with FDG-avid lesions, 33 patients (56%) received work up with ultrasound, thyroid technetium scintigraphy, fine needle aspiration, and/or histology of which 20 patients had a conclusive pathology report. Ten patients with FDG-avid lesions were identified with thyroid malignancy. The risk of thyroid malignancy was 16.9% among patient with incidental FDG-avid thyroid lesions. Our findings indicated a similar frequency of FDG thyroid incidentalomas and malignancy rates in an iodine deficient population compared to summary data from prior studies, studies mostly performed in geographical areas of normal or excess iodine supplementation.

Evidence-based management of incidental focal uptake of fluorodeoxyglucose on PET-CT

Focal incidental uptake, with or without CT abnormalities, is a common finding on fluorodeoxyglucose PET/CT and evidence-based management for this type of uptake is lacking. This article reviews the evidence on focal incidental uptake including the incidence of malignancy, differential diagnosis and imaging criteria which can be used to further characterize it. The article focusses on PET rather than CT criteria. The strength of the evidence base is highly variable ranging from systematic reviews and meta-analyses to a virtual absence of evidence. Caution needs to be used when using standardized uptake values (SUVs) reported in other studies due to interpatient and institution observed variation in SUVs. There is sufficient evidence to permit specific suggestions on how to interpret the foci and recommend further management in the: pituitary (investigate when SUVmax >4.1), thyroid (investigate all), breast (investigate all), lung parenchyma (if focus of fluorodeoxyglucose without a CT nodule, no further investigations), colon (investigate all foci with SUVmax >5.9, urgently if SUVmax >11.4), adrenals (criteria depend on if patient has cancer) and prostate gland (investigate in males aged >50 years or >40 years if peripheral uptake or patient has other risk factors). There is some evidence to guide further management for the parotid gland, naso-orophaynx, oesophagus, pancreas, uterus and ovaries. There is insufficient evidence to guide management for the liver, spleen, kidneys, gallbladder, testis and bone, for these organs patient characteristics and other guidelines will likely be of more use in determining further management.

Hypermetabolic Thyroid Incidentaloma on Positron Emission Tomography: Review of Laboratory, Radiologic, and Pathologic Characteristics

Introduction

Incidental hypermetabolic thyroid lesions on Positron Emission Tomography have significant clinical value and may harbor malignancy. In this study we evaluated laboratory, radiologic, and pathologic characteristics of incidental hypermetabolic thyroid lesions.

Materials and Methods

We evaluated 18 patients prospectively with various malignancies and hypermetabolic thyroid incidentaloma. The thyroid function tests, ultrasound assessment, and guided FNA biopsy were performed on all cases.

Results

We included 9 male and 9 female patients with mean age of 51 years. Most common malignancy was colon cancer. Metabolic activity quantification using maximum standard uptake value demonstrated range between 1.4 and 65.4 with mean value of 9.4. We found highest metabolic activity in patients with lung adenocarcinoma, B-cell lymphoma, and colon adenocarcinoma. On ultrasound exam most thyroid lesions were of solid, hypoechoic, noncalcified nature with either normal or peripheral increased vascularity. FNA biopsy report was benign in 15 cases and malignant or highly suggestive for malignancy in 3 other cases. Two of the three malignant cases demonstrated metabolic activity higher than average SUV max.

Conclusion

Most thyroid hypermetabolic incidentalomas are benign lesions, while higher values of SUV max are in favor of malignancy. This mandates further evaluation of incidentally found thyroid hypermetabolic lesions on routine PET/CT scans.

The incidence of thyroid cancer in focal hypermetabolic thyroid lesions: an 18F-FDG PET/CT study in more than 6000 patients

BACKGROUND

The clinical significance of incidental thyroid abnormalities discovered in fluorine-18 fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) (FDG PET/CT) studies remains controversial. The aim of this large retrospective study was to (a) determine the prevalence of focal F-FDG thyroid uptake on whole-body F-FDG PET/CT studies carried out for nonthyroid cancers and (b) to test whether intense focal F-FDG thyroid uptake is associated with malignancy.

MATERIALS AND METHODS

A total of 11 921 F-FDG PET/CT studies in 6216 patients carried out at our institution between January 2012 and December 2014 were analyzed. We retrospectively reviewed the medical records of these patients. Eight hundred and forty-five/6216 (13.6%) patients had a thyroid incidentaloma on the basis of the clinical F-FDG PET/CT report. One hundred and sixty/845 (18.9%) of these underwent ultrasound and 98 (61.3%) of these underwent a fine-needle aspiration (FNA). Twenty-six of these 98 (26.5%) patients underwent thyroidectomy. Thyroid lesion and background standardized uptake value (SUVs) for each patient were measured upon review of the F-FDG PET/CT study. We measured maximum standardized uptake value (SUVmax), thyroid to background TL/TBG, thyroid to bloodpool TL/BP and thyroid to liver TL/L ratios in benign and malignant lesions. Receiver operating curves were calculated to determine optimal cut-off values between malignant and benign lesions.

RESULTS

Twenty-one of the 98 patients who underwent FNA biopsy or thyroidectomy had malignant disease (21.4%). Malignant lesions had significantly higher thyroid lesion SUVmax, TL/TBG, TL/BP, and TL/L than benign nodules. The receiver operating curves derived cut-off ratio TL/TBG of more than 2.0 differentiated benign from malignant lesions best with a specificity and sensitivity of 0.76 and 0.88, respectively.

CONCLUSION

The incidence of malignancy in biopsied focal hypermetabolic thyroid lesions is 21.4%. Lesions on F-FDG PET/CT studies, with a ratio TL/TBG more than 2.0, warrant further work-up with ultrasound and FNA to exclude malignancy.

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.

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.

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.

Unusual Uptake of Prostate Specific Tracer 68Ga-PSMA-HBED-CC in a Benign Thyroid Nodule

⁶⁸Ga-Prostate specific membrane antigen- N,N'-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N'-diacetic acid- positron emission tomography/computed tomography or 68 Ga- HBED-CC-PSMA PET/CT, popularly known as PSMA PET/CT, is able to detect a small volume of recurrent prostate carcinoma (PC) when there is a prostate specific antigen (PSA) rise on follow-up after prostatectomy or other definitive treatment for PC. The use of PSMA PET/CT in the initial staging in PC is uncertain at this time. Clinical studies are underway to define its exact role in the management of the disease. At the same time it is important to be aware of unexpected sites of uptake of this ligand. We present here the case of a 62-year-old male patient who underwent prostatectomy for adenocarcinoma prostate. He also had a long-standing left solitary thyroid nodule (STN). Four months after surgery, he had a rising trend in serum PSA levels on three occasions, but the absolute value was less than 4 at all times. He underwent a ⁶⁸Ga-PSMA-HBED-CC PET/CT, but it did not reveal any recurrent/metastatic site of disease. However, there was increased tracer uptake in the left STN. Fine needle aspiration cytology revealed features of atypia of undetermined significance, Bethesda category III. The patient underwent a left hemithyroidectomy and the histopathology showed features of a follicular adenoma.

Risk Stratification of Thyroid Incidentalomas Found on PET/CT: The Value of Iodine Content on Noncontrast Computed Tomography

BACKGROUND

The Hounsfield unit (HU) ratio of thyroid nodules was assessed compared to the contralateral thyroid lobe on noncontrast computed tomography (CT) to stratify further the risk of malignancy in thyroid incidentalomas found on 18F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography/CT (PET/CT).

METHODS

This retrospective analysis included 82 patients who had thyroid incidentalomas on PET/CT in 2011. On PET/CT, the maximal standardized uptake value ratios of the thyroid nodule compared to liver (T/BSUV) and the HU ratios of the thyroid nodule compared to contralateral thyroid lobe (T/BHU) were calculated. Diagnostic performances of the T/BSUV and T/BHU were compared.

RESULTS

The area under the curve of T/BHU was higher than that of T/BSUV (0.941 vs. 0.689, p < 0.0001). The sensitivity, specificity, and accuracy of T/BHU were significantly higher than those of T/BSUV (100% vs. 77.8%, p = 0.0313; 80.0% vs. 60.0%, p = 0.0433; 86.6% vs. 65.9%, p = 0.0041, respectively). The risk of malignancy was much higher (71.1%) in nodules with a T/BHU cutoff value ≤0.68, whereas it was 0% in nodules with a T/BHU of >0.68. In this study, there were 18 nodules with nondiagnostic (n = 7) or atypia of undetermined significance or follicular lesion of undetermined significance cytologies (n = 11) after fine-needle aspiration biopsy (FNAB). When the T/BHU cutoff value was applied, three (60%) of the five nodules with a T/BHU of ≤0.68 were found to be papillary carcinomas. The remaining 13 nodules with a T/BHU of >0.68 were all benign with a risk of malignancy of 0%.

CONCLUSIONS

T/BHU is a simple and effective parameter to stratify the risk of malignancy in thyroid incidentalomas found on PET/CT. This may be of clinical relevance in those nodules with nondiagnostic or undetermined significance cytologies upon FNAB in the scheme of current clinical practice.

Diffusion-weighted and PET/MR Imaging after Radiation Therapy for Malignant Head and Neck Tumors

Interpreting imaging studies of the irradiated neck constitutes a challenge because of radiation therapy-induced tissue alterations, the variable appearances of recurrent tumors, and functional and metabolic phenomena that mimic disease. Therefore, morphologic magnetic resonance (MR) imaging, diffusion-weighted (DW) imaging, positron emission tomography with computed tomography (PET/CT), and software fusion of PET and MR imaging data sets are increasingly used to facilitate diagnosis in clinical practice. Because MR imaging and PET often yield complementary information, PET/MR imaging holds promise to facilitate differentiation of tumor recurrence from radiation therapy-induced changes and complications. This review focuses on clinical applications of DW and PET/MR imaging in the irradiated neck and discusses the added value of multiparametric imaging to solve diagnostic dilemmas. Radiologists should understand key features of radiation therapy-induced tissue alterations and potential complications seen at DW and PET/MR imaging, including edema, fibrosis, scar tissue, soft-tissue necrosis, bone and cartilage necrosis, cranial nerve palsy, and radiation therapy-induced arteriosclerosis, brain necrosis, and thyroid disorders. DW and PET/MR imaging also play a complementary role in detection of residual and recurrent disease. Interpretation pitfalls due to technical, functional, and metabolic phenomena should be recognized and avoided. Familiarity with DW and PET/MR imaging features of expected findings, potential complications, and treatment failure after radiation therapy increases diagnostic confidence when interpreting images of the irradiated neck. Online supplemental material is available for this article.

Evaluation of clinical presentation and referral indications for ultrasound-guided fine-needle aspiration biopsy of the thyroid as possible predictors of thyroid cancer

BACKGROUND

Whether initial clinical presentation and thyroid ultrasonography referral indications can significantly predict malignant/suspicious for malignancy (Bethesda System for Reporting Thyroid Cytopathology [Bethesda] V/VI) thyroid ultrasound-guided fine-needle aspiration (FNA) cytology results is unknown.

METHODS

Between January 2010 and May 2014, we performed 705 thyroid ultrasound-guided FNA biopsies, according to the American Thyroid Association (ATA) guidelines. Univariate analysis was used to identify significant predictors for Bethesda V/VI thyroid ultrasound-guided FNA cytology, including age, sex, imaging modality, thyroid dysfunction, neck pain, breathing difficulties, dysphagia, odynophagia, fatigue, lateral cervical mass, parotid mass, and hyperparathyroidism.

RESULTS

Sixty percent of patients were referred to thyroid ultrasound-guided FNA because of thyroid incidentalomas and 40% because of palpable thyroid nodules found on physical examination. Only positron emission tomography (PET)-CT emerged as being a significant predictor for Bethesda V/VI thyroid ultrasound-guided FNA cytology (odds ratio [OR] = 5.64; 95% confidence interval [CI] = 1.16-27.33; p = .03).

CONCLUSION

Patient symptomatology and initial clinical thyroid ultrasound-guided FNA referral indications cannot predict the nature of thyroid nodules. © 2015 Wiley Periodicals, Inc. Head Neck 38: E991-E995, 2016.

Benign and Malignant Thyroid Incidentalomas Are Rare in Routine Clinical Practice: A Review of 97,908 Imaging Studies

PURPOSE

Thyroid nodules incidentally identified on imaging are thought to contribute to the increasing incidence of thyroid cancer. We aim to determine the true rate of incidental thyroid nodule reporting, malignancy rates of these nodules, and to compare these findings with rates of detection by dedicated radiology review.

METHODS

A cross-sectional analysis was done to determine the prevalence of thyroid nodules in radiologist reports by analyzing all reports for CT, PET, and MRI scans of the head, neck, and chest as well as neck ultrasounds performed at a tertiary care center from 2007 to 2012. Retrospective chart review was performed on patients with a reported thyroid nodule to determine clinical outcomes of these nodules. Radiology reports were compared with dedicated radiology review of 500 randomly selected CT scans from the study group to determine the difference between clinical reporting and actual prevalence of thyroid nodules.

RESULTS

97,908 imaging studies met inclusion criteria, and 387 (0.4%) thyroid incidentalomas were identified on radiology report. One hundred and sixty three (42.1%) of these nodules were worked up with fine-needle aspiration, diagnosing 27 thyroid cancers (0.03% of all studies, 7.0% of reported incidentalomas). The prevalence of incidentalomas clinically reported was 142/100,000 CT scans, 638/100,000 MRIs, 358/100,000 PET scans, and 6,594/100,000 ultrasounds. In contrast, review of CT scans screening for thyroid nodules had a prevalence of 10%.

CONCLUSION

Routine clinical reporting of incidental thyroid nodules is far less common than on dedicated review.

IMPACT

These data contradict the notion that incidentalomas contribute significantly to rising thyroid cancer rates.