Role of combined 18F-FDG-PET/CT for predicting the WHO malignancy grade of thymic epithelial tumors: A multicenter analysis

Evaluation of the effect of PET/CT Fluorodeoxyglucose inclusion on mortality and survival in operated thymoma patients

PURPOSE

In recent years, the use of fluorodeoxyglucose PET-computed tomography (PET-CT) has become widespread to evaluate the diagnosis, metabolism, stage and distant metastases of thymoma. In this study, it was aimed to investigate the connection of malignancy potential, survival and maximum standardized uptake value (SUV max ) measured by PET-CT before surgery according to the histological classification of the WHO in patients operated for thymoma. In addition, the predictive value of the Glasgow prognostic score (GPS) generated by C-reactive protein (CRP) and albumin values on recurrence and survival was investigated and its potential as a prognostic biomarker was evaluated.

METHODS

Forty-five patients who underwent surgical resection for thymoma and were examined with PET-CT in the preoperative period between January 2010 and January 2022 were included in the study. The relationship between WHO histological classification, tumor size and SUV max values on PET-CT according to TNM classification of retrospectively analyzed corticoafferents were evaluated. Preoperative albumin and CRP values were used to determine GPS.

RESULTS

The cutoff value for SUV max was found to be 5.65 in the patients and the overall survival rate of low-risk (<5.65) and high-risk (>5.65) patients was compared according to the SUV max threshold value (5.65) and found to be statistically significant. In addition, the power of PET/CT SUV max value to predict mortality (according to receiver operating characteristics analysis) was statistically significant ( P  = 0.048). Survival expectancy was 127.6 months in patients with mild GPS (O points), 96.7 months in patients with moderate GPS (1 point), and 25.9 months in patients with severe GPS (2 points).

CONCLUSION

PET/CT SUV max values can be used to predict histological sub-type in thymoma patients, and preoperative SUV max and GPS are parameters that can provide information about survival times and mortality in thymoma patients.

Is PET/CT Able to Predict Histology in Thymic Epithelial Tumours? A Narrative Review

BACKGROUND

The usefulness of ¹⁸FDG PET/CT scan in the evaluation of thymic epithelial tumours (TETs) has been reported by several authors, but data are still limited and its application in clinical practice is far from being defined.

METHODS

We performed a narrative review of pertinent literature in order to clarify the role of ¹⁸FDG PET/CT in the prediction of TET histology and to discuss clinical implications and future perspectives.

RESULTS

There is only little evidence that ¹⁸FDG PET/CT scan may distinguish thymic hyperplasia from thymic epithelial tumours. On the other hand, it seems to discriminate well thymomas from carcinomas and, even more, to predict the grade of malignancy (WHO classes). To this end, SUVmax and other PET variables (i.e., the ratio between SUVmax and tumour dimensions) have been adopted, with good results. Finally, however promising, the future of PET/CT and theranostics in TETs is far from being defined; more robust analysis of imaging texture on thymic neoplasms, as well as new exploratory studies with "stromal PET tracers," are ongoing.

CONCLUSIONS

PET may play a role in predicting histology in TETs and help physicians in the management of these insidious malignancies.

Multiparametric Magnetic Resonance Imaging for Assessing Thymic Epithelial Tumors: Correlation With Pathological Subtypes and Clinical Stages

BACKGROUND

World Health Organization classification and Masaoka-Koga stage are widely used for thymic epithelial tumors (TETs). Reduced field-of-view (rFOV) diffusion-weighed imaging (DWI) proved to improve the image quality. Dynamic contrast-enhanced (DCE) MRI was commonly used in evaluating tumors.

PURPOSE

To investigate the value of multiparametric MRI in evaluating TETs.

STUDY TYPE

Retrospective.

SUBJECTS

Eighty-seven participants including 38 low risk (52.08 ± 14.19 years), 30 high risk (52.40 ± 11.35 years), and 19 thymic carcinoma patients (59.76 ± 10.78 years).

FIELD STRENGTH/SEQUENCE

A 3 T, turbo spin echo imaging, echo planar imaging, volumetric interpolated breath-hold examination with radial acquisition trajectory.

ASSESSMENT

DCE-MRI and apparent diffusion coefficient (ADC) variables were compared. Diagnostic performances of single significant factor and combined model were compared.

STATISTICAL TESTS

Parameters were compared using one-way ANOVA or independent-samples t test. Logistic regression was employed to investigate the combined model. Receiver operating curves (ROC) and DeLong's test were used to compare the diagnostic efficiency.

RESULTS

ADC, K^trans , and k_ep values were significantly different among low-risk, high-risk and carcinoma group (ADC, 1.279 ± 0.345 × 10^-3  mm² /sec, 0.978 ± 0.260 × 10^-3  mm² /sec, 0.661 ± 0.134 × 10^-3  mm² /sec; K^trans 0.167 ± 0.071 min^-1 , 0.254 ± 0.136 min^-1 , 0.393 ± 0.110 min^-1 ; k_ep 0.345 ± 0.113 min^-1 , 0.560 ± 0.269 min^-1 , 0.872 ± 0.149 min^-1 ). They were significantly different for early stage and advanced stage (ADC, 1.270 ± 0.356 × 10^-3  mm² /sec vs. 0.845 ± 0.251 × 10^-3  mm² /sec; K^trans 0.179 ± 0.092 min^-1 vs. 0.304 ± 0.142 min^-1 ; k_ep 0.370 ± 0.181 min^-1 vs. 0.674 ± 0.362 min^-1 ). The combination of them had highest diagnostic efficiency for WHO classification (AUC, 0.925; sensitivity, 83.7%; specificity, 89.5%), clinical stage (AUC, 0.879; sensitivity, 80.9%; specificity, 82.5%).

DATA CONCLUSION

Multiparametric MRI model may be useful for discriminating WHO classification and clinical stage of TETs.

EVIDENCE LEVEL

4 TECHNICAL EFFICIENCY: Stage 2.

Usefulness of positron-emission tomography for predicting the World Health Organization grade of thymic epithelial tumors

Background

It is often difficult to distinguish between thymoma and thymic carcinoma by preoperative radiological tests. While there have been some reports that the maximum standardized uptake value (SUV_max) in positron emission tomography‐computed tomography (PET‐CT) is useful to this end, no large‐scale analysis has been performed. We therefore analyzed the usefulness of the SUV_max and tumor size (TS) for differentiating thymic epithelial tumors.

Methods

From 2011 to 2019, 129 patients with thymic epithelial tumor who underwent PET‐CT before surgical treatment were enrolled. The relevance of the SUV_max to the World Health Organization (WHO) histological type was assessed. To reduce the impact of the TS, the ratio of the SUV_max to the TS was also investigated.

Results

A total of 99 thymoma cases and 30 thymic carcinoma cases were enrolled into the study. The SUV_max and SUV_max/TS of thymic carcinoma were significantly higher than those of thymoma (SUV_max: 7.7 ± 3.4 vs. 3.3 ± 1.3, p < 0.01; SUV_max/TS: 1.5 ± 0.7 vs. 0.6 ± 0.4, p < 0.01). Focusing on the patients with a moderate SUV_max of ≤5 (84 thymoma and 4 thymic carcinoma), the SUV_max/TS values of thymic carcinoma were still significantly higher than those of thymoma (1.6 ± 0.8 vs. 0.6 ± 0.4, p < 0.01).

Conclusions

PET‐CT might provide significant information for differentiating images of thymoma and thymic carcinoma. We experienced several cases of thymic carcinoma with a moderate SUV_max of ≤5, and SUV_max/TS was considered a useful parameter for differentiating such cases.

Imaging Evaluation of Thymoma and Thymic Carcinoma

Imaging is integral in the management of patients with thymoma and thymic carcinoma. At initial diagnosis and staging, imaging provides the clinical extent of local invasion as well as distant metastases to stratify patients for therapy and to determine prognosis. Following various modalities of therapy, imaging serves to assess treatment response and detect recurrent disease. While imaging findings overlap, a variety of CT, MRI, and PET/CT characteristics can help differentiate thymoma and thymic carcinoma, with new CT and MRI techniques currently under evaluation showing potential.

Usefulness of 18F-FDG PET/CT in treatment-naive patients with thymic squamous cell carcinoma

OBJECTIVE

Thymic squamous cell carcinoma (TSCC) is very rare. This study aims to investigate the clinical utility of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in treatment-naive patients with TSCC.

METHODS

The tumor metabolic parameters of ¹⁸F-FDG PET/CT, including maximum standard uptake value (SUVmax), metabolic tumor volume of primary lesion (MTV-P) and combination of primary lesion and metastases (MTV-C), and total lesion glycolysis of primary lesion (TLG-P) and combination of primary lesion and metastases (TLG-C) were collected. Age, sex, smoking, serum tumor markers, tumor size, Masaoka-Koga stage, TNM stage, contrast-enhanced CT scan, and tumor immunity were also reviewed. Moreover, progression-free survival (PFS) and overall survival (OS) of these patients were analyzed.

RESULTS

Forty-two treatment-naive patients with TSCC were enrolled in this study. All primary tumors were FDG-avid with the average SUVmax of 10.0 ± 4.5 (range, 1.5-20.4). Higher SUVmax, MTV-C, and TLG-C were observed in advanced Masaoka-Koga stage than early stage, and higher SUVmax was found in advanced TNM stage than early stage. Next, 36 out of 42 patients performed chest contrast-enhanced CT scan, which showed SUVmax associated with the enhancement degree of CT. Moreover, 27 out of 42 lesions were assessed tumor immunity, and the detective rates of PD-L1, PD-1, CD4, CD8, and Foxp3 were 59.3%, 37.0%, 59.3%, 100%, and 77.8%, respectively. Higher SUVmax was observed in lesions with lower CD4-positive tumor-infiltrating lymphocytes. Furthermore, 12- and 24-month PFS and OS rates were 62.0% vs 32.8% and 84.5% vs 68.9%, respectively. Multivariate Cox regression analysis showed that only MTV-C was an independent predictor of PFS.

CONCLUSION

¹⁸F-FDG PET/CT is useful in evaluating tumor staging, assessing CT enhancement degree, and detecting tumor immunity of TSCC before treatment. ¹⁸F-FDG PET/CT could also be a promising tool to provide prognostic information for treatment-naive patients with TSCC.

Lymph Node Dissection in Thymoma: Is it worth it?

OBJECTIVES

Lymph node dissection (LND) and nodal metastases in thymomas remain controversial and understudied. The aim of our study was to evaluate the incidence of nodal metastasis and the short term outcomes of systematic LND in thymomas.

MATERIAL AND METHODS

From December 2017 to September 2020, we performed 54 LND conducted according to the International Thymic Malignancy Interest Group (ITMIG) lymph node map. This group was compared to a historical control group of 55 patients who underwent surgery in our center from January 2015 to November 2017.

RESULTS

LND was performed in 72 % and in 5 % of the cases in the study cohort group and historical control group, respectively. The number of lymph nodes retrieved was significantly higher in the study cohort group (3.89 per patient vs. 1.62, p = 0.0021). In the whole population studied, nodal metastases were found in 3 patients (2.8 % of all patients) with 5.6 % in the cohort study group vs. 0 % in the control group (p = 0.12). Patients with nodal metastasis had larger tumors (> 7 cm), and a higher histology grade (B2 and B3). There was a trend towards higher risk of laryngeal nerve palsy in the cohort study group (9.3 % vs. 1.8 %, p = 0.11).

CONCLUSION

Systematic LND increases the number of lymph node harvested and detects more lymph node metastases, which remains infrequent in thymomas. The impact of LND and the true prognostic significance of lymph node metastases remains controversial. Given the potential complications, LND or sampling should not be perfomed in small, encapsulated and low grade thymomas.

The usefulness of fluorodeoxyglucose-positron emission tomography as a preoperative diagnostic tool for thymic epithelial tumors

Background

To investigate the usefulness of ¹⁸F-fluorodeoxy glucose-positron emission tomography (¹⁸F-FDG PET) for the preoperative imaging diagnosis of malignant grade in thymic epithelial tumors (TETs) and the correlation between the maximum standardized uptake value (SUVmax) and tumor size in TETs.

Methods

We retrospectively investigated 51 patients with TETs performed ¹⁸F-FDG PET. The SUVmax was compared between thymic carcinomas and thymomas. We also evaluated the difference in the SUVmax limited to small TETs. In addition, the correlation between the SUVmax and the tumor size was evaluated.

Results

The mean SUVmax of thymic carcinomas (n=12) and thymomas (n=39) was 5.71±2.6 and 3.08±1.4, respectively. The SUVmax of thymic carcinomas was significantly higher than that of thymomas (P<0.001). The mean SUVmax of these small thymic carcinomas (n=3) and thymomas (n=13) was 2.97±0.24 and 1.79±0.47, respectively. The SUVmax of the small thymic carcinomas was significantly higher than that of the thymomas (P=0.001). We found a positive correlation between the SUVmax and the maximum tumor size of TETs (correlation coefficient: 0.632, P<0.001).

Conclusions

¹⁸F-FDG PET might be useful for evaluating the preoperative malignancy of TETs. Of note, the maximum tumor size should be considered when performing assessments by ¹⁸F-FDG PET.

Value of 18F-FDG PET/computed tomography in predicting the simplified WHO grade of malignancy in thymic epithelial tumors

OBJECTIVE

To investigate the value of 18F-fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) in predicting the simplified WHO grade of malignancy in thymic epithelial tumors.

MATERIALS AND METHODS

We retrospectively reviewed 81 patients with pathologically proven thymic epithelial tumors who underwent F-FDG PET/CT before surgical resection. Maximum standardized uptake value (SUVmax) and SUVmax/tumor size were measured on the primary lesion. A receiver operating characteristics (ROC) curve were performed for assessing the ability of F-FDG PET/CT as a predictor of the simplified WHO classification.

RESULTS

There were 43 male patients (53.1%) and 38 female patients (46.9%), and the mean age was 55.6 ± 11.9 years. The mean tumor size was 53.2 ± 21.4 mm. There were 24 low-risk thymomas (29.6%) (A, AB, and B1), 29 high-risk thymomas (35.8%) (B2 and B3), and 28 thymic carcinomas (34.6%). The SUVmax and SUVmax/tumor size were found to be predictive factors that were useful to distinguish thymomas and thymic carcinomas, and area under the ROC curve were 0.820 and 0.691, respectively (P < 0.05), and the cutoff value for discriminating thymomas and thymic carcinomas was 5.34.

CONCLUSION

In conclusion, a significant relationship was observed between SUVmax, SUVmax/tumor size and histological WHO classification of thymic epithelial tumors. F-FDG PET/CT may be useful for predicting the grade of malignancy in thymic epithelial.

18F-FDG-PET/CT predicts grade of malignancy and invasive potential of thymic epithelial tumors

PURPOSE

The aim of this study was to evaluate the ability of fluorine-18-fluorodeoxyglucose positron emission tomography coupled with computed tomography (18F-FDG-PET/CT) to predict the WHO malignancy grade, initial staging, and invasive potential of thymic epithelial tumors.

METHODS

We retrospectively reviewed the medical records of 56 patients with thymic epithelial tumors who were evaluated by PET/CT before surgery and underwent surgical resection. We analyzed the relationship of the maximum standardized uptake value (SUVmax) with the WHO histological classification, tumor invasion, TNM classification, and the Masaoka-Koga classification.

RESULTS

There were differences of SUVmax of the FDG-PET between thymic carcinoma (9.09 ± 3.34) and thymoma (4.86 ± 2.45; p < 0.01), thymic carcinoma (9.09 ± 3.34) and high-grade thymoma (6.01 ± 2.78; p < 0.01), and high-grade thymoma (6.01 ± 2.78) and low-grade thymoma (4.06 ± 1.86; p < 0.01). The cut-off value for the SUVmax was 7.40 and 5.40, and the sensitivity/specificity for predicting the histologic subtype of each group was 0.72/0.79 and 0.61/0.85, respectively. According to T classification, SUVmax was significantly higher in T3 (8.31 ± 2.57) than in T1a (4.45 ± 2.06; p < 0.01). Regarding Masaoka-Koga classification and WHO histological classification, a significantly higher SUVmax was detected in patients with stage III and IV disease than in those with stage I and II diseases (p < 0.01). The cut-off value for SUVmax was 5.40 in Masaoka-Koga stage and 5.60 in the WHO classification; the sensitivity/specificity for predicting the histologic subtype was 0.85/0.80 and 0.89/0.78, respectively.

CONCLUSIONS

FDG-PET is a useful tool to predict aggressiveness of thymic epithelial tumors.

Pretreatment serum neutrophil-to-lymphocyte and monocyte-to-lymphocyte ratios: Two tumor-related systemic inflammatory markers in patients with thymic epithelial tumors

OBJECTIVES

To understand underlying changes in pretreatment serum inflammatory markers associated with thymic epithelial tumors (TETs) development.

METHODS

A retrospective analysis of 113 TETs patients who underwent 18-fluorine fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography combined computed tomography (PET/CT) one to two weeks before tumor resection or biopsy was performed. Pretreatment serum neutrophil, monocyte, platelet, and lymphocyte counts, and fibrinogen and C-reaction protein (CRP) concentrations were measured one day before surgery or biopsy. Neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and platelet-to-lymphocyte ratio (PLR) were calculated by dividing corresponding cells counts by lymphocyte counts, respectively. The maximum standard uptake value (SUVmax) of ¹⁸F-FDG of primary TETs was applied to reflect tumor glycolytic activity. The student's t-test, one-way ANOVA analysis, Chi-square test, receiver operating characteristic curve analysis, and Logistic regression analysis were used for statistical analysis.

RESULTS

The serum NLR and MLR were significantly higher in TETs patients than in healthy volunteers (P both ≤ 0.001). High serum NLR and MLR were related to the thymic carcinomas (TCs) subtype, elevated Masaoka-Koga (M-K) tumor stage, and metastasis of TETs (P all < 0.005). High serum NLR and MLR were also associated with high SUVmax values of TETs (P all < 0.005), with increasingly differences between groups as the cut-off values defining low-SUVmax and high-SUVmax groups increased. With the medium cutoff of NLR, MLR, and SUVmax of 3.07, 0.25, and 8.00 respectively, the high NLR and MLR levels were significantly associated with high SUVmax level of TETs (P both < 0.005). Moreover, the incidences of co-high SUVmax/NLR and co-high SUVmax/MLR were higher in TETs patients older than 55 years, with TCs, in M-K stage IV, and with metastasis (P all < 0.05). Both the co-high SUVmax/NLR and co-high SUVmax/MLR increased the risk of TETs metastasis (P both < 0.001), while the co-high SUVmax/MLR was also an independent risk factor for TETs metastasis (odds ratio: 3.92, 95% confidence interval: 1.02-15.12, P = 0.047).

CONCLUSION

Pretreatment serum NLR and MLR of TETs patients are two tumor-progression- and tumor-glycolysis-related inflammatory markers. Enhanced tumor glycolytic activity and associated systemic inflammatory reaction may play a synergistic role in TETs metastasis.

Quantitative analysis of metabolic parameters at 18F-fluorodeoxyglucose positron emission tomography in predicting malignant potential of anterior mediastinal tumors

To evaluate the utility of ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) for predicting the malignancy of anterior mediastinal tumors, the present study retrospectively examined a total of 105 consecutive patients who underwent surgical resection of anterior mediastinal tumors at Gunma University Hospital after undergoing a preoperative FDG-PET scan. Patients were divided into benign and malignant groups in accordance with the following three classification systems: i) Clinical classification, benign or malignant (thymoma and carcinoma); ii) recurrence-based classification, low-risk recurrence (benign and low-risk thymoma) or high-risk recurrence (high-risk thymoma and carcinoma); and iii) pathological classification, benign (benign and thymoma) or malignant (carcinoma). The present study analyzed the differences between the benign and malignant groups in terms of FDG-PET parameters, including maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG). The malignant group exhibited a significantly greater SUVmax than the benign group according to all classification systems. By contrast, there was only a slight difference between groups in volume-based metabolic parameters (MTV and TLG) using the clinical classification, and no intergroup differences using the recurrence-based and pathological classifications. The area under the curve in receiver-operating characteristic curve analysis for predicting malignancy was significantly greater for SUVmax than for volume-based metabolic parameters using all classification methods. The respective optimal cut-off value, sensitivity and specificity of SUVmax to predict malignancy were 1.77, 92.0 and 87.0% for the clinical classification, 2.54, 93.6 and 60.3% for the recurrence-based classification, and 5.15, 78.9 and 90.7% for the pathological classification. SUVmax was the most useful parameter for predicting the malignancy of anterior mediastinal tumors.

Can 18F-FDG PET predict the grade of malignancy in thymic epithelial tumors? An evaluation of only resected tumors

Objective

Although 18-fluorine fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) is thought to be useful for predicting the histological grade of thymic epithelial tumors (TETs), it remains controversial. To date, just a few of many previous studies have included only resected cases. Therefore, we investigated ¹⁸F-FDG PET findings only in patients with resected TETs.

Patients and methods

A total of 112 patients with TETs consisting of 92 thymomas and 20 thymic carcinomas (TCs), resected at two institutes (Shizuoka Cancer Center [Shizuoka] and National Cancer Center Hospital [Tokyo]) between October 2002 and December 2015, were evaluated. Spearman rank correlation coefficient was used to assess the association between the maximum standardized uptake value (SUVmax) in the tumor and both the histological subtype and tumor stage. The cutoff value of SUVmax for differentiating thymoma from TC was calculated.

Results

The SUVmax was strongly related to both the World Health Organization (WHO) histological subtype and tumor stage based on the eighth edition of the tumor-node-metastasis (TNM) classification (Spearman rank correlation coefficient =0.485 and 0.432; p = 0.000 and 0.000, respectively). There was a significant difference between thymoma and TC. The optimal SUVmax cutoff value for differentiating thymoma from TC was 4.58 (sensitivity: 80% and specificity: 78.3%). In contrast, there was no significant difference between low-risk (type A, AB, and B1) and high-risk (type B2 and B3) thymoma, or between type B3 thymoma and the other subtypes.

Conclusion

Our results suggest that ¹⁸F-FDG PET is useful for differentiating thymoma from TC, but not for predicting the histologic grade of thymoma.

Positron Emission Tomography in Thymic Tumors: Analysis Using a Prospective Research Database

BACKGROUND

Positron emission tomography may have a role in the pretreatment workup of patients with thymic malignancies. This study was undertaken to determine the utility of the maximum standardized uptake value (SUV_max) in predicting histologic type and tumor stage in a large cohort of thymic epithelial tumors.

METHODS

The large, multiinstitutional, prospective database of The International Thymic Malignancy Interest Group (ITMIG) was queried for the use of positron emission tomography in the pretreatment workup of patients with thymic tumors. Data analyzed included demographics, SUV_max, histologic tumor type, and tumor stage. The distribution of SUV_max according to histologic type and Masaoka-Koga pathologic stage was determined, and the ability of SUV_max to predict these two variables was calculated using analysis of receiver operating characteristic curves.

RESULTS

Since 2012, data from 926 patients with thymic malignancies were entered into the ITMIG prospective database, of which 154 had a reported value for SUV_max. The area under the receiver operating characteristic curve for SUV_max in predicting histologic type and pathologic stage was 0.79 (95% confidence interval, 0.70 to 0.88; p < 0.001) and 0.81 (95% confidence interval, 0.73 to 0.88; p < 0.001), respectively. In addition, there was a significant relationship between SUV_max and histologic type (p < 0.001) as well as Masaoka-Koga pathologic stage (p < 0.001).

CONCLUSIONS

Positron emission tomography has utility in predicting clinicopathologic features of thymic malignancies. These results may have clinical application in the pretreatment workup of patients with these rare tumors.

Occasional detection of thymic epithelial tumor 4 years after diagnosis of adult onset Still disease: A challenging case report and immuno-oncological considerations coming from pertinent literature review

BACKGROUND

Thymoma is a T cell neoplasm arising from the thymic epithelium that due to its immunological role, frequently undercover derangements of immunity such a tumors and autoimmune diseases.

METHODS

Herein, we report, to the best of our knowledge, the first description of an association between thymoma and adult onset Still disease (AOSD) in a 47-year-old man. The first one was occasionally detected 4 years later the diagnosis of AOSD, and surgically removed via right lateral thoracotomy. Histology confirmed an encapsulated thymic tumor (type AB sec. WHO-classification).

RESULTS

The AOSD was particularly resistant to the therapy, requiring a combination of immunosuppressant followed by anti-IL1R, that was the only steroids-sparing treatment capable to induce and maintain the remission. The differential diagnosis was particularly challenging because of the severe myasthenic-like symptoms that, with normal laboratory tests, were initially misinterpreted as fibromyalgia. The pathogenic link of this association could be a thymus escape of autoreactive T lymphocytes causing autoimmunity.

CONCLUSION

Clinicians should be always include the possibility of a thymoma in the differential diagnosis of an unusual new onset of weakness and normal laboratories data, in particular once autoimmune disease is present in the medical history.

Value of 18F-FDG PET/CT for Predicting the World Health Organization Malignant Grade of Thymic Epithelial Tumors: Focused in Volume-Dependent Parameters

PURPOSE

We investigated whether preoperative parameters of 18F-FDG PET/CT were correlated with the World Health Organization (WHO) classification and/or Masaoka staging of thymic epithelial tumors.

PATIENTS AND METHODS

We reviewed 61 patients retrospectively who were diagnosed with thymic epithelial tumors after surgical resection and PET/CT. A volume of interest was drawn on the primary lesion, using an SUV cutoff of 2.5, and metabolic indices such as SUVmax, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured.

RESULTS

There were 24 male patients (38.7%), and the mean (SD) age was 50.23 (12.54) years. The mean (SD) tumor size was 6.11 (3.41) cm. There were 22 low-risk thymomas (36.9%) (A, AB, B1), 32 high-risk thymomas (51.6%), and 7 thymic carcinomas (11.5%). The Masaoka stage was I in 15 (24.6%), II in 30 (49.2%), III in 11 (18.0%), and IV in 5 patients (8.2%). Mean (SD) SUVmax was 3.43 (1.01) in low-risk thymomas, 4.42 (1.70) in high-risk thymomas, and 8.23 (2.61) in thymic carcinoma; the differences were significant (P < 0.001). Mean (SD) MTV and TLG were 90.74 (114.56) and 229.36 (300.56) in low-risk thymomas, 80.82 (112.49) and 233.93 (340.91) in high-risk thymomas, and 90.63 (90.74) and 390.94 (437.62), respectively, in thymic carcinomas. MTV and TLG showed no correlation with the WHO classification. On receiver operating characteristic curve analysis, the cutoff value for discriminating thymomas and thymic carcinomas was 5.05. SUVmax and TLG were correlated with Masaoka stage.

CONCLUSIONS

Although volume-dependent parameters were not correlated with the WHO classification, a significant relationship was observed between SUVmax and WHO classification and Masaoka stage.

FDG PET/CT Manifestation of Rare Widespread Metastatic Chemoradiation-Refractory Thymic Squamous Cell Carcinoma

A 74-year-old man underwent excisional biopsy of an anterior mediastinal mass that revealed squamous cell carcinoma of thymic origin. Immunohistochemistry revealed insulin-like growth factor-1 receptor positivity, which has been associated with worse prognosis. Restaging FDG PET/CT revealed extensive soft tissue and osseous metastases despite surgery and chemoradiation therapy. Patient was then enrolled in a clinical trial with anti-insulin-like growth factor-1 receptor therapy. A 3-month follow-up FDG PET/CT showed disease progression with an increase in size and number of hypermetabolic metastatic lesions, including interval development of multiple new metastases.

Conflicting or complementary role of computed tomography (CT) and positron emission tomography (PET)/CT in the assessment of thymic cancer and thymoma: our experience and literature review

Background

To evaluate the role of computed tomography (CT) and positron emission tomography (PET)/CT in patients with thymic cancer and thymoma at initial staging.

Methods

We retrospectively reviewed CT and PET/CT scans of 26 patients with a thymic cancer (n = 9) or thymoma (n = 17). Chest CT findings documented were qualitative and quantitative. Both qualitative and semiquantitative data were recovered by PET/CT. The comparisons among histological entities, outcome, and qualitative data from CT and PET/CT were made by non-parametric analysis.

Results

PET/CT resulted positive in 15/17 patients with thymoma. CT was available in 5/9 (56%) patients with thymic cancer and in 3/17 with thymoma. All quantitative CT parameters were significantly higher in patients with thymic cancer than thymoma (maximum axial diameter: 45 vs. 20 mm, maximum longitudinal diameter: 69 vs. 21 mm and volume: 77.91 vs. 4.52 mL; all P < 0.05). Conversely, only metabolic tumor volume (MTV) and total lesion glycolysis were significantly different in patients with thymic cancer than thymoma (126.53 vs. 6.03 cm3 and 246.05 vs. 20.32, respectively; both P < 0.05). After a median follow-up time of 17.45 months, four recurrences of disease occurred: three in patients with thymic cancer and one with a type B2 thymoma. CT volume in patients with recurrent disease was 102.19 mL versus a median value of 62.5 mL in six disease-free patients. MTV was higher in the recurrent than disease-free patient subset (143.3 vs. 81.13 cm³), although not statistically significant (P = 0.075).

Conclusion

Our preliminary results demonstrated that both morphological and metabolic volume could be useful from a diagnostic and prognostic point of view in thymic cancer and thymoma patients. A large multi-center clinical trial experience for confirming the findings of this study seems mandatory.

Predicting subtypes of thymic epithelial tumors using CT: new perspective based on a comprehensive analysis of 216 patients

It is highly necessary to identify low versus high risk thymic epithelial tumors (TETs) before operation to guide optimal treatment strategies. Current CT diagnostic parameters could not effectively achieve this goal. We evaluated three parameters of CT scan in a cohort of 216 TETs patients. Parameters of contrast enhancement, risk of aggressiveness, and nodule with fibrous septum were evaluated in low (A, AB) versus high risk (B1, B2, B3 and thymic carcinoma) TETs. Grade of contrast enhancement showed predictive value in classifying low and high risk TETs well. A maximal contrast-enhanced range of 25.5 HU could produce 78.8% sensitivity and 68.5% specificity in determining low risk subtypes. Additionally, risk of aggressiveness parameter was demonstrated to be associated with TETs subtype (r = 0.801, P < 0.001) and may add confidence in determining low versus high risk subtypes. Furthermore, multiple nodule with fibrous septum could suggest subtype AB. Findings from this study support role of studied parameters of CT manifestations in predicting the low and high risk stages of TETs. These findings provide empirical evidence for incorporating these parameters in clinical practice for identifying TETs stage before operation, if validated in additional studies.

Is (18)F-FDG PET useful in predicting the WHO grade of malignancy in thymic epithelial tumors? A meta-analysis

AIM

To perform a systematic review and meta-analysis of published data on the role of fluorine-18-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) in predicting the WHO grade of malignancy in thymic epithelial tumors (TETs).

METHODS

A comprehensive literature search of studies published up to March 2014 was performed. Data on maximum standardized uptake value (SUVmax) in patients with low-risk thymomas (A, AB, B1), high-risk thymomas (B2, B3) and thymic carcinomas (C) according to the WHO classification were collected when reported by the retrieved articles. The comparison of mean SUVmax between low-risk thymomas, high-risk thymomas and thymic carcinomas was expressed as weighted mean difference (WMD) and a pooled WMD was calculated including 95% confidence interval (95%CI).

RESULTS

Eleven studies were selected for the meta-analysis. The pooled WMD of SUVmax between high-risk and low-risk thymomas was 1.2 (95%CI: 0.4-2.0). The pooled WMD of SUVmax between thymic carcinomas and low-risk thymomas was 4.8 (95%CI: 3.4-6.1). Finally, the pooled WMD of SUVmax between thymic carcinomas and high-risk thymomas was 3.5 (95%CI: 2.7-4.3).

CONCLUSIONS

(18)F-FDG PET may predict the WHO grade of malignancy in TETs. In particular, we demonstrated a statistically significant difference of SUVmax between the different TETs (low-grade thymomas, high-grade thymomas and thymic carcinomas).