Increased 18F-FDG uptake mimicking thyroid cancer in a patient with Hashimoto's thyroiditis

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.

Imaging of head and neck mucosa-associated lymphoid tissue lymphoma (MALToma)

Marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALToma) arises in extranodal sites in the head and neck. Chronic inflammatory, infectious or autoimmune conditions are implicated in its pathogenesis. Within the head and neck, MALToma is often multifocal and indolent and the imaging appearances may be mistaken for non-malignant disease in the head and neck. The aim of this article is to illustrate the varied radiological and clinical features of MALToma in the head and neck, an awareness of which is needed for timely and correct diagnosis to guide subsequent disease management.

The Role of 18F-FDG PET/CT in the Management of the Autoimmune Thyroid Diseases

Objective: It is a well-known fact that positron emission tomography (PET) is an effective tool in the assessment of thyroid focal lesions, however only few studies so far have investigated its role in monitoring of autoimmune thyroid diseases (AITDs). The aim of this study is to assess if PET scan may be useful for the assessment of the thyroid gland in patients with an AITD-Hashimoto's thyroiditis. Methods: We evaluated twenty subjects with diagnosed Hashimoto's thyroiditis (proven by presence of elevated thyroid antibodies level and by thyroid imaging). The maximum standardized uptake value (SUV-max) of the thyroid parenchyma was measured using ¹⁸F-FDG-PET/CT. Control group consisted of patients who have been in carcinoma remission for other reasons than thyroid cancer and who had been investigated by PET scan to exclude carcinoma recurrence. All control group subjects had their thyroid glands intact, none of them had a medical history of thyroid disease including thyroid nodules. AITDs had been excluded in all control group subjects. STATISTICA 13.1 software was used for statistical analysis. Results: Results: The SUV-max was significantly higher in patients with an AITD than in healthy subjects (median SUV-max 3.94 vs. 1.95; p = 0.005). Conclusions: ¹⁸F-FDG-PET/CT scan may differentiate normal thyroid parenchyma from the diffused inflammatory changes of the thyroid gland in patients with AITDs. However, the researchers must be continued.

Positron emission tomography/computed tomography scan of Vogt-Koyanagi-Harada syndrome with associated autoimmune thyroid disease: A case report and literature review

RATIONALE

Vogt-Koyanagi-Harada (VKH) syndrome is a rare disease and could be associated with autoimmune thyroid disease (AITD). This report was aimed to investigate the utility of F-fludeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) for the diagnosis of VKH syndrome with AITD and to perform a literature review on the association between the 2 diseases.

PATIENT CONCERNS

A 55-year-old woman without the history of ocular trauma suffered from chronic headache. She was presented with painful blurred vision of both eyes with headache for 2 weeks. Ophthalmic evaluations revealed panuveitis, exudative retinal detachment, and papilloedema in both eyes. The clinical symptoms and presentations are compatible with the diagnosis of VKH syndrome. Other examinations for intraocular infection, malignancy, and lupus choroidopathy were of negative results. The result of contrast-enhanced computed tomography (CT) of the brain was normal. Due to the history of cancer in the patient's families, a F-FDG PET/CT whole-body scan was performed. The result indicated a focal of 2-fluoro-2-deoxy-D-glucose (FDG) uptake at the right upper lobe of the thyroid. Therefore, the patient's thyroid function was examined and the result indicated euthyroidism with detectable thyroid peroxidase/thyroglobulin antibodies.

DIAGNOSES

VKH syndrome with associated AITD.

INTERVENTIONS

Treatment with intravenous pulse systemic methylprednisolone (1000 mg daily) was prescribed for 3 days and then shifted gradually to tapered oral steroid medication.

OUTCOMES

Symptoms of papillitis and serous retinal detachment of VKH syndrome was relieved after steroid treatment LESSONS:: F-fludeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) can be used for the effective diagnosis of VKH syndrome with AITD.

Surgical Treatment of Primitive Thyroid Lymphoma

Aims and Background

Primitive thyroid lymphoma, although rare, is becoming more frequent. Its incidence is increasing, from 0.5% in the sixties to 1-5% of all thyroid neoplasms today. The diagnosis of such neoplasms is not always straightforward. In fact, it is often the result of pathologic findings on a gland resected for an apparently benign disease. Surgical dissection may prove more complicated than in standard cases of thyroidectomy for the possible tight adhesions existing between the gland's capsule and the surrounding structures. In cases of capsular infiltration, postoperative external local radiotherapy is indicated.

Methods

A retrospective observational analysis was performed to establish whether patients with incidental thyroid lymphomas who underwent total thyroidectomy for another pathology had major surgical complications and worse prognostic results than patients with an accurate preoperative diagnosis.

Results

Six cases of thyroid lymphoma were retrospectively reviewed: 4 diffuse large B-cell lymphomas and 2 MALT lymphomas. Of these, 2 were correctly preoperatively identified by fine-needle aspiration biopsy and 4 were an unexpected finding at histology: 3 cases of total thyroidectomy carried out for huge hypothyroid goiter in patients affected by Hashimoto's thyroiditis and in 1 case of total thyroidectomy carried out for anaplastic carcinoma in a patient affected by Hashimoto's thyroiditis.

Conclusions

In our experience, a correct preoperative diagnosis was extremely difficult (33%). In patients who underwent fine-needle aspiration, a correct diagnosis was made in 66% of cases. All patients with stage IE lymphoma who underwent total thyroidectomy had equivalent surgical complications and prognosis.

The Accuracy of 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in the Evaluation of Bone Lesions of Undetermined Origin

The aim of the current study was to determine the diagnostic accuracy of whole-body fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in detecting carcinoma of unknown primary (CUP) with bone metastases. We evaluated 87 patients who were referred to FDG-PET/CT imaging and reported to have skeletal lesions with suspicion of malignancy. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated. The median survival rate was measured to evaluate the prognostic value of the FDG-PET/CT findings. In the search for a primary, FDG-PET/CT findings correctly diagnosed lesions as the site of the primary true positive (TP) in 64 (73%) cases, 4 (5%) findings diagnosed no site of a primary, and none were subsequently proven to be true negative (TN); 14 (16%) diagnoses were false positive (FP) and 5 (6%) diagnoses were false negative (FN). Life expectancy was between 2 months and 25 months. Whole-body FDG-PET/CT imaging may be a useful method in assessing the bone lesions with suspicion of bone metastases.

Subacute thyroiditis presenting as a focal lesion on [18F] fluorodeoxyglucose whole-body positron-emission tomography/CT

A 52-year-old man presented with subacute thyroiditis and showed an intensely hypermetabolic thyroid lesion on (18)F-FDG PET/CT. The patient also had coexisting chronic lymphocytic thyroiditis. The lesion of subacute thyroiditis revealed an SUV(max) of 9.1 g/mL and was ill-defined, heterogeneous, markedly hypoechoic, and hypovascular on US. Biopsy demonstrated histologic findings of subacute thyroiditis, which should be included in the differential diagnosis of an intensely hypermetabolic thyroid lesion on (18)F-FDG PET/CT.

Systematic review: prevalence of malignant incidental thyroid nodules identified on fluorine-18 fluorodeoxyglucose positron emission tomography

PURPOSE

To review current literature and determine the prevalence of malignant incidental focal hypermetabolic thyroid lesions detected by fluorine-18 fluorodeoxyglucose positron emission tomography (F-FDG-PET).

MATERIALS AND METHODS

Studies evaluating thyroid carcinomas discovered incidentally on F-FDG-PET were systematically searched in the MEDLINE, CINAHL, and Evidence-Based Medicine (EBM) Reviews from 1998 to 2007. Studies were eligible for inclusion with the following criteria: F-FDG-PET studies carried out on humans, long-term clinical follow-up or presence of histological confirmation of thyroid disease, and if studies reported the prevalence of abnormal F-FDG-PET scans with thyroid lesions and confirmed pathological thyroid disease. Studies were excluded if (1) there was no confirmed diagnosis, (2) there was a history of thyroid cancer, (3) they were carried out for diagnoses of thyroid abnormalities, or (4) they were case series. Two reviewers independently reviewed each study's eligibility and abstracted the data.

RESULTS

Eighteen articles met criteria resulting in a total of 55 160 patients with 571 patients (1%) having an unexpected focal abnormality in the thyroid gland. Diagnostic confirmations were obtained in 322 patients. Among the confirmed diagnoses, 200 (62.1%) were benign, 107 (33.2%) were malignant, and 15 (4.7%) were indeterminate or a patient without a clear diagnosis. Papillary thyroid carcinoma was the most prevalent thyroid malignancy (82.2%). Eight studies reporting individual maximum standard uptake values were included in a subanalysis. The mean maximum standard uptake value for 73 benign lesions was 4.6+/-2.1, and for the 52 malignant lesions was 6.8+/-4.6 (P<0.001).

CONCLUSION

The high prevalence of malignancy associated with focal hypermetabolic thyroid nodules found on F-FDG-PET warrants further evaluation when detected.

Imaging features of primary extranodal lymphomas

Lymphomas are generally considered tumours of lymph nodes, but up to 40% arise extranodally. This group shows distinctive pathological, radiological, and clinical features. Different subtypes of extranodal lymphoma may show sufficiently specific radiological features to be of significant value in both establishing a diagnosis of lymphoma and ascertaining the exact subtype. Rapidly evolving lymphoma classifications and emergence of new entities have, however, hampered the accurate description of these features in the literature. In this review, we discuss the radiological appearances, using a variety of imaging methods, of the full spectrum of primary extranodal lymphomas, categorized according to the current World Health Organisation classification.

Role of fluorodeoxyglucose-PET versus fluorodeoxyglucose-PET/computed tomography in detection of unknown primary tumor: a meta-analysis of the literature

The objectives of this study were to evaluate the diagnostic accuracy of fluorodeoxyglucose (FDG)-PET and FDG-PET/computed tomography (CT) in the detection of primary tumors in patients presenting with carcinoma of unknown primary (CUP) unidentified by conventional workup, and to compare the statistical difference between the FDG-PET and FDG-PET/CT. Twenty-eight studies (involving a total of 910 patients) published between 1990 and 2007 were reviewed. These studies evaluated the role of FDG-PET and FDG-PET/CT in the detection of unknown primary tumors after physical examination and conventional workup failed to detect a primary tumor. Systematic methods were used to identify, select, and evaluate the methodological quality of the studies as well as to summarize the overall findings of sensitivity, specificity, and detection capacity of the primary tumor. The overall sensitivity and specificity of FDG-PET in detecting unknown primary tumors were 0.78 [95% confidence interval (CI): 0.72-0.84)] and 0.79 (95% CI: 0.74-0.83), respectively. Furthermore, FDG-PET detected 28.54% of tumors that were not apparent after CUP failed to be detected by conventional workup. Data were collected on the locations of primary tumors detected by FDG-PET in 17 studies and detected by FDG-PET/CT in seven studies. Tumors from the base of the tongue accounted for 20.7% (six of 29) of all false-positive FDG-PET scans, corresponding to a false-positive rate of 28.6% (six of 29), much higher than tumors from the others. FDG-PET exhibited a lower sensitivity with respect to the tumors at the base of the tongue and tonsils, which was 68.2 and 76.7%, respectively. In the eight studies with 430 patients diagnosed with CUP by FDG-PET/CT, 31.4% (n=135) of primary tumors were detected. The pooled sensitivity and specificity were 0.81 (95% CI: 0.74-0.87) and 0.83 (95% CI: 0.78-0.87), respectively. FDG-PET and FDG-PET/CT can detect primary tumors that went undetected by physical examination and conventional workup. FDG-PET exhibited lower sensitivity with respect to the tumors at the base of the tongue and the tonsils.

Avaliação pré-operatória com PET-18F-FDG de nódulos de tireóide com citologia indeterminada

Esse artigo tem o objetivo de discutir o papel da tomografia por emissão de pósitrons (PET) com 18F-FDG na avaliação pré-operatória de pacientes com nódulos de tireóide com citologia indeterminada. Para o cálculo da sensibilidade, foram selecionados todos os estudos com pacientes com carcinoma de tireóide. Para o cálculo da especificidade, foram selecionados apenas estudos desenhados para avaliação dos pacientes com nódulos com citologia indeterminada. O achado de captação focal na PET-18F-FDG relacionou-se com a presença de carcinoma de tireóide na maioria dos estudos. A sensibilidade do exame foi bastante alta na detecção de malignidade tireoidiana, porém sua especificidade variou de 0% a 66%, sendo de 39% em estudo brasileiro. Concluindo, os estudos indicam que a PET-18F-FDG pode reduzir o número de tireoidectomias desnecessárias em pacientes com nódulos de tireóide com citologia indeterminada. Entretanto, o percentual relativamente elevado de resultados falso-positivos, o alto custo, a baixa disponibilidade do exame em países em desenvolvimento e a pouca experiência clínica ainda limitam o uso da PET-18F-FDG com essa finalidade.

Clinical significance of focal and diffuse thyroid diseases identified by 18F-fluorodeoxyglucose positron emission tomography

(18)F-Fluorodeoxyglucose positron emission tomography (FDG-PET) thyroid incidentalomas are defined abnormal FDG uptake in the thyroid gland found at PET scan performed as part of a staging protocol and follow-up of patients with various kinds of malignancies. In the present study we report two cases of FDG PET thyroid incidentalomas, and review the literature with regard to the meaning of this new category of thyroid "disease". Since the advent of whole body FDG PET scan, a relatively high incidence of cases of thyroid FDG uptake has been reported as an incidental finding as in one of our patient. Focal uptake was found to be more likely associated to a malignant lesion, while a diffuse thyroid uptake to a benign thyroid disease. However, differential diagnosis is difficult, and reported data in literature are somewhat discordant. A focal thyroid uptake of FDG incidentally discovered at PET scan cannot be invariably considered a malignant thyroid nodule, however a prompt and complete work-up including laboratory examinations, ultrasonography and fine needle aspiration cytology, should be obtained to exclude a thyroid carcinoma. On the other hand, patients with a PET finding of diffuse FDG uptake can be considered at low risk of malignancy, being more likely associated to chronic thyroiditis or diffuse thyroid autonomy.

Diffuse and diffuse-plus-focal uptake in the thyroid gland identified by using FDG-PET: prevalence of thyroid cancer and Hashimoto's thyroiditis

OBJECTIVE

To investigate and evaluate the prevalence of incidental thyroid diffuse and diffuse-plus-focal fluorine-18 fluorodeoxyglucose (FDG) uptake in healthy subjects who underwent cancer screening on positron emission tomography (PET) scan, and also to evaluate the prevalence of thyroid cancer and Hashimoto's thyroiditis.

METHODS

We carried out a retrospective review of 1626 subjects who underwent PET scanning at our institution. Diffuse uptake was defined as FDG uptake in the whole thyroid gland, whereas diffuse-plus-focal uptake was defined as a thyroid lesion with both diffuse uptake and focal FDG uptake. The maximum standardized uptake value of the thyroid lesions was recorded and reviewed. In each selected subject with positive thyroid FDG uptake, serum thyroid-stimulating hormone, thyroid hormone, and thyroid antibodies were measured. Fine needle aspiration cytology was performed on patients with a definite nodule using ultrasonography.

RESULTS

Twenty-nine subjects (1.78%) were identified as having either diffuse FDG uptake (n = 25, 1.53%) or diffuse-plus-focal FDG uptake (n = 4, 0.24%). All subjects with diffuse FDG uptake were diagnosed as having Hashimoto's thyroiditis. In 1 of the 25 subjects with diffuse FDG uptake and two of the four with diffuse-plus-focal FDG uptake, histopathologic diagnosis showed papillary thyroid carcinoma associated with Hashimoto's thyroiditis. However, PET scan did not detect papillary carcinoma associated with Hashimoto's thyroiditis in one of the three subjects.

CONCLUSIONS

Our results suggest that although diffuse FDG uptake usually indicates Hashimoto's thyroiditis, the risk of thyroid cancer must be recognized in both diffuse FDG uptake and diffuse-plus-focal FDG uptake on PET scan.

The value of quantifying 18F-FDG uptake in thyroid nodules found incidentally on whole-body PET–CT

OBJECTIVE

To determine if quantification of [18F]fluorodeoxyglucose (18F-FDG) uptake in a thyroid nodule found incidentally on whole-body 18F-FDG positron emission tomography-computed tomography (PET-CT) can be used to discriminate between malignant and benign aetiology.

METHODS

A retrospective review of all patients with focally high uptake in the thyroid as an incidental finding on 18F-FDG PET-CT from May 2003 through May 2006. The uptake in the nodules was quantified using the maximum standardized uptake value (SUVmax). The aetiology was determined by cytology and/or ultrasound, or on histopathology.

RESULTS

Incidental focally high uptake was found in 79/7347 patients (1.1%). In 31/48 patients with adequate follow-up, a benign aetiology was determined. Median SUVmax for the benign group was 5.6, range 2.5-53. Malignancy was confirmed in 15/48 patients. The malignancies were papillary thyroid carcinoma in 12, metastasis from squamous cell carcinoma in one, and lymphoma in two. Median SUVmax for the malignant lesions was 6.4, range 3.5-16. Cytology suspicious for follicular carcinoma was found in 2/48 patients. No statistical difference (P=0.12) was found among the SUVmax between the benign and malignant groups.

CONCLUSION

Focally high uptake of 18F-FDG in the thyroid as an incidental finding occurred in 1.1% of the patients. Malignancy was confirmed or was suspicious in 17/48 (35%) of the patients that had adequate follow-up. There was no significant difference in the SUVmax between benign and malignant nodules.

Mismatch of F-18 Fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) and Tc-99m Pertechnetate Single Photon Emission Computed Tomography (SPECT) in a Euthyroid Multinodular Goiter

Imaging results of F-18 fluorodeoxyglucose (FDG) PET/CT scanning and Tc-99m pertechnetate scintigraphy of the thyroid gland are described and compared with pathology in a patient who was followed after left nephrectomy for renal cell carcinoma diagnosed 10 years earlier. On F-18 FDG PET/CT scanning, a multinodular struma with increased localized F-18 FDG uptake in 4 nodules was seen. Two nodules with increased glucose metabolism appeared normal on Tc-99m pertechnetate scintigraphy. Pathology indicated hyperplastic nodules. High focal F-18 FDG uptake was also seen in a lesion that corresponded with a "cold" nodule on Tc-99m pertechnetate scintigraphy, suggesting malignant disease. However, pathology revealed hyperplastic nodules with a background of aspecific lymphocytic thyroiditis. A fourth nodule with increased F-18 FDG uptake appeared mixed ("cold"/"hot") on Tc-99m pertechnetate scintigraphy. On pathology, a well-differentiated follicular carcinoma was found. These findings, in a single patient, illustrate the wide spectrum of matched and mismatched F-18 FDG and Tc-99m pertechnetate thyroid uptake along with their variable pathologic correlates.

Evolving role of positron emission tomography in the management of patients with inflammatory and other benign disorders

Fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has evolved from a research imaging modality assessing brain function in physiologic and pathologic states to a pure clinical necessity. It has been successfully used for diagnosing, staging, and monitoring a variety of malignancies. FDG-PET imaging also is evolving into a powerful imaging modality that can be effectively used for the diagnosis and monitoring of a certain nononcological diseases. PET has been shown to be very useful in the diagnosis of osteomyelitis, painful prostheses, sarcoidosis, fever of unknown etiology, and acquired immunodeficiency syndrome. Based on recent observations, several other disorders, such as environment-induced lung diseases, atherosclerosis, vasculitis, back pain, transplantation, and blood clot, can be successfully assessed with this technique. With the development and the introduction of several new PET radiotracers, it is expected that PET will secure a major role in the management of patients with inflammatory and other benign disorders.

Lobar mucinous bronchioloalveolar carcinoma of the lung showing negative FDG uptake on integrated PET/CT

We present a case of bronchioloalveolar carcinoma manifesting as air-space consolidation with negative FDG uptake on integrated PET/CT in a 42-year-old woman. To know this pattern of uptake especially in the case of mucin-predominant lobar bronchioloalveolar carcinoma may help avoid misdiagnosis of this particular tumor.

Applications of fluorodeoxyglucose-PET imaging in the detection of infection and inflammation and other benign disorders

FDG-PET has great potential in the evaluation of a variety of inflammatory and infectious disorders and possibly other benign disorders. FDG-PET is very helpful in the evaluation of chronic osteomyelitis, sarcoidosis, FUO, and differentiating toxoplasmosis from lymphoma in the central nervous system in HIV-positive patients. The assessment of efficacy of FDG-PET in the evaluation of arthroplasty-associated infection, large-vessel vasculitis, and other inflammatory and infectious disorders is ongoing but seems quite promising at this time.

Investigation of thyroid, head, and neck cancers with PET

PET with [(18)F]-fluorodeoxyglucose (FDG) has been accepted as a useful imaging modality for the diagnosis of a variety of malignancies. This article discusses the use of FDG-PET in the management of patients with thyroid and head or neck cancers.