Clinical Management of Thymoma Patients

Analysis of Pulmonary Function in Thymoma Subjects: A 20-Year Retrospective Cohort Study

BACKGROUND

Thymoma is the most common tumor of the anterior mediastinum. However, the correlation between thymoma stage and pulmonary function was not assessed. Our objective in this study was to describe the pulmonary function in thymoma subjects stratified with different staging systems.

METHODS

A total of 143 subjects with a diagnosis of thymoma who underwent extended thymectomy for thymoma between January 2001 and December 2019 were reviewed retrospectively. All the subjects experienced pulmonary function tests (PFTs) using Master Screen PFT system and total respiratory resistance measurement.

RESULTS

We evaluated 143 subjects with a diagnosis of thymoma; the significant differences were observed in mean values of vital capacity, inspiratory volume (IC), total lung capacity (TLC), ratio of residual volume to total lung capacity (RV/TLC), forced vital capacity, forced expiratory volume in 1 second, ratio of forced expiratory volume in 1 second to forced vital capacity, peak expiratory flow, peak inspiratory flow, maximum ventilation volume, total airway resistance, and diffusing capacity for carbon monoxide (DLCO) across upper airway obstruction classification. PFTs of subjects with varying Masaoka stages are different. RV and RV/TLC of subjects in stages III and IV were higher than those of normal level, while DLCO of subjects in stage IV was lower than the normal level, and the mean level of IC showed significant difference between stage II and stage III.

DISCUSSION

The pulmonary function patterns of thymoma subjects significantly correlate with tumor location and size rather than clinical Masaoka stage.

Intrapericardial Thymoma Presented as Pericardial Tamponade with Post-Operative Myasthenia Gravis

Background: Thymoma is an epithelial mass arising from the thymus. Most thymomas are located in the anterior mediastinum. Ectopic intrapericardial thymoma is very unusual; to date, only eight cases of pericardial thymoma have been reported. Among thymoma patients, 20% to 25% are associated with myasthenia gravis. However, postoperative myasthenia gravis occurs in less than 1% of cases. Here, we share a rare case of ectopic intrapericardial thymoma that developed postoperative myasthenia gravis six months after surgery. Case presentation: A 66-year-old woman visited the outpatient department due to productive cough and chest pain. Chest radiography showed increased soft tissue opacity over the mediastinum. A soft tissue mass in the pericardium and a ground glass nodule in right upper lung were noted using chest computed tomography. The diagnosis of thymoma, type B2, pT3N0M0, and stage IIIA and synchronous adenocarcinoma in situ of the right upper lung was confirmed after surgical removal. Six months later, the patient developed postoperative myasthenia gravis. Conclusions: Thymoma is rarely considered a differential diagnosis in pericardial tumors. Surgical removal with adjuvant radiation therapy should be performed considering the malignancy potential of thymomas and cardiac complications. In patients without myasthenia gravis, a small chance of postoperative myasthenia gravis remains. Patients should be carefully monitored for myasthenia gravis after surgery.

Comparison between CT and MRI in the Diagnostic Accuracy of Thymic Masses

Purpose: The aim of this study was to compare diagnostic accuracy between CT and MRI for thymic masses.

Methods: We searched literature and collected information on first author, publication year, cases of different types of thymic lesions, correct diagnostic cases of CT and MRI and results of quantitative analysis of CT and MRI. The ROC curve was applied to compare the diagnostic performance of different imaging modalities.

Results: Eight literatures were finally included and analyzed in this study. There were 253 cases examined by CT and 340 cases by MRI in total. We showed outcomes of quantitative analysis of each study in this article. The sensitivity of CT and MRI was both 100%, while the specificity was 75% and 80%, respectively. AUC of CT was 0.875 [95%CI: 0.473, 0.997] and that of MRI was 0.880 [95%CI: 0.531, 0.995].

Conclusion: The diagnostic accuracy of MRI is superior to CT in detecting thymomas, thymic cysts or thymic hyperplasia but that of CT and MRI is still unclear in differentiating thymic carcinomas and lymphomas/germ cell tumors.

Long-term survival after R0 resection of thymoma

Background The aim of this study was to evaluate the results of R0 resection of thymoma to identify prognostic factors for long-term outcomes. Methods Data of 62 patients (28 male, 34 female) with a mean age of 47.26 ± 14.42 years, who underwent R0 resection for thymoma and were followed-up between February 2004 and March 2016, were analyzed retrospectively. Results Eight patients had a video-assisted thoracoscopic thymectomy and 54 had a transsternal extended thymectomy. During a mean follow-up of 128.67 ± 7.95 months, regional recurrence of thymoma was observed in 9 (14.5%) patients. Overall 5- and 10-year survival rates were 85.36% and 78.20%, respectively. The 5- and 10-year survival rates in patients aged < 50 years were significantly better than in those aged ≥ 50 years (92% and 72% vs. 88% and 39%, p < 0.0001). The 10-year overall survival of patients in Masaoka stage I and II was better than those in stage III (88.9%, 78.4%, 69.8%, respectively, log-rank p < 0.001). The 10-year survival of patients with World Health Organization histological type A, AB, and B1 thymomas was better than those with type B2 and B3 (log-rank test p < 0.001). In multivariate analysis, age < 50 years ( p = 0.001), Masaoka stage ( p = 0.006), histological type ( p = 0.001), and recurrence ( p = 0.04) were independent prognostic factors for survival. Conclusion Our study indicates that age < 50 years, Masaoka stage, histological type, and recurrence are the determinants of survival in surgically resected cases of thymoma.

[Pretreatment Biopsy for Histological Diagnosis and Induction Therapy in Thymic Tumors]

背景与目的

探讨术前病理学诊断在胸腺肿瘤诊断和治疗中的价值及其对胸腺肿瘤治疗的影响。

方法

对中国胸腺肿瘤协作组（Chinese Alliance for Research in Thymomas, ChART）收集的1994年-2012年的多中心且具有明确活检状态的胸腺肿瘤患者的临床病理资料进行回顾性分析，探讨术前病理学诊断的应用趋势及其对胸腺肿瘤患者预后的影响。

结果

1, 902例胸腺肿瘤患者中，术前病理学诊断患者336例（17.1%）。近年来术前病理学诊断的比例较前明显增加（P=0.008），胸腔镜/纵隔镜/超声内镜下经支气管活检（endobronchial ultrasound, E-BUS）比例较前升高（P=0.029）。术前行病理学诊断患者的生存明显差于无病理学诊断患者（P < 0.001），术前病理学诊断后的目的与肿瘤的Masaoka分期（P < 0.001）、切除程度（P=0.025）、病理类型（P < 0.001）具有相关性。术前病理学诊断后直接手术患者的生存要明显优于诱导治疗后再手术患者（P < 0.001）。

结论

胸腺瘤诊断主要依靠临床及组织学判断，近年来术前病理学诊断在胸腺肿瘤的诊断和治疗中起重要作用；根治性手术切除是胸腺肿瘤的首先治疗手段；术前病理学诊断后直接手术患者的预后要明显优于诱导治疗后患者。

The spectrum of ectopic thymomas

Thymomas are rare tumors that usually manifest in the anterosuperior mediastinum. Occasionally, thymomas may also originate from ectopically dispersed thymic tissue and can arise in locations such as the neck, lung, or pleura or other locations in the thoracic cavity. The occurrence of thymomas in these ectopic locations can cause substantial diagnostic difficulty as the entity is almost never included in the differential diagnosis and its biphasic morphology can cause further complications during the diagnostic process. In this review, we summarize the clinical and pathological spectrum of ectopic thymomas and discuss the histogenesis, treatment, and prognosis of these extraordinary tumors.

Pretreatment biopsy for histological diagnosis and induction therapy in thymic tumors

BACKGROUND

This study was to investigate the value of pretreatment biopsy for histological diagnosis and induction therapies in the management of locally advanced thymic malignancies.

METHODS

The clinical pathological data of patients with thymic tumors in the Chinese Alliance for Research in Thymomas (ChART) who underwent biopsy before treatment from 1994 to December 2012 were retrospectively reviewed. The application trend of preoperative histological diagnosis and its influence on treatment outcome were analyzed.

RESULTS

Of 1,902 cases of thymic tumors, 336 (17.1%) had undergone biopsy for histological diagnosis before therapeutic decision was decided. In recent years, percentage of pretreatment histological diagnosis significantly increased in the later ten years than the former during the study period (P=0.008). There was also a significant increase in thoracoscopy/mediastinoscopy/E-BUS biopsy as compared to open biopsy (P=0.029). Survival in Patients with preoperative biopsy for histology had significantly higher stage lesions (P=0.000) and higher grade malignancy (P=0.000), thus a significantly lower complete resection rate (P=0.000) and therefore a significantly worse survival than those without preoperative biopsy (P=0.000). In the biopsied 336 patients, those who received upfront surgery had significantly better survival than those received surgery after induction therapy (P=0.000). In stage III and IVa diseases, the R0 resection rate after induction therapies increased significantly as compared to the surgery upfront cases (65.5% vs. 46.2%, P=0.025). Tumors downstaged after induction had similar outcomes as those having upfront surgery (92.3% vs. 84.2%, P=0.51). However, tumors not downstaged by induction had significantly worse prognosis than those downstaged (P=0.004), and fared even worse than those having definitive chemoradiation without surgery (37.2% vs. 62.4%, P=0.216).

CONCLUSIONS

It is crucial to get histological diagnosis for thymoma before surgery or adjuvant treatment and minimally invasive biopsy should be undertaken. Although in our study we could not find the benefit of induction chemotherapy before surgery in survival and recurrence rate, it could increase the R0 resection rate compared with direct surgery in late stage (III and IVa).

State of the Art: MR Imaging of Thymoma

Thymoma is the most common primary malignancy of the anterior mediastinum and the most common thymic epithelial neoplasm, but it is a rare tumor that constitutes less than 1% of adult malignancies. Computed tomography (CT) is currently the imaging modality of choice for distinguishing thymoma from other anterior mediastinal masses, characterizing the primary tumor, and staging the disease. However, magnetic resonance imaging is also effective in evaluating and characterizing anterior mediastinal masses and staging thymoma in patients with contraindications to contrast-material-enhanced CT such as contrast allergy and/or renal failure.

State of the art: diagnostic tools and innovative therapies for treatment of advanced thymoma and thymic carcinoma

In this review article, state-of-the-art diagnostic tools and innovative treatments of thymoma and thymic carcinoma (TC) are described with special respect to advanced tumour stages. Complete surgical resection (R0) remains the standard therapeutic approach for almost all a priori resectable mediastinal tumours as defined by preoperative standard computed tomography (CT). If lymphoma or germ-cell tumours are differential diagnostic considerations, biopsy may be indicated. Resection status is the most important prognostic factor in thymoma and TC, followed by tumour stage. Advanced (Masaoka-Koga stage III and IVa) tumours require interdisciplinary therapy decisions based on distinctive findings of preoperative CT scan and ancillary investigations [magnetic resonance imaging (MRI)] to select cases for primary surgery or neoadjuvant strategies with optional secondary resection. In neoadjuvant settings, octreotide scans and histological evaluation of pretherapeutic needle biopsies may help to choose between somatostatin agonist/prednisolone regimens and neoadjuvant chemotherapy as first-line treatment. Finally, a multimodality treatment regime is recommended for advanced and unresectable thymic tumours. In conclusion, advanced stage thymoma and TC should preferably be treated in experienced centres in order to provide all modern diagnostic tools (imaging, histology) and innovative therapy techniques. Systemic and local (hyperthermic intrathoracic chemotherapy) medical treatments together with extended surgical resections have increased the therapeutic options in patients with advanced or recurrent thymoma and TC.

Thymoma of the Left Thymic Lobe with a Contralateral Small Pleural Implant Successfully Detected with Diffusion-weighted MRI

Thymoma is the most common primary neoplasm of the anterior mediastinum. At diagnosis, up to 40% of patients present with advanced disease. Because advanced thymomas receive neoadjuvant chemotherapy, diagnostic imaging is crucial to plan the correct treatment. For characterizing thymomas, CT is the first choice modality, whereas 18F-FDG/PET is reserved for questionable cases and MRI is not routinely employed. Hereby, we describe a case of thymoma with a single contralateral pleural implant in a 30-year-old woman. The small pleural thickening detected at CT was correctly interpreted as pleural seeding related to thymoma at diffusion-weighted (DW)-MRI after a negative 18F-FDG/PET scan, and was subsequently confirmed at surgery. Precise diagnosis and accurate preoperative staging are crucial in managing thymic epithelial tumours in order to design the appropriate treatment and improve prognosis. Indeed, when stage IVa for pleural seeding is diagnosed preoperatively, a multimodality approach including primary chemotherapy followed by surgery and postoperative radiotherapy/chemotherapy is recommended. This is the first report that used DW-MRI for the characterization of pleural seeding in thymoma and demonstrates that DW-MRI could be useful for the correct pre-operatory staging in thymoma patients, especially in cases with indeterminate pleural thickenings at CT, in order to define the correct management.

Preoperative computed tomography findings predict surgical resectability of thymoma

INTRODUCTION

The aim of the study was to identify preoperative computed tomography (CT) imaging characteristics that correlated with surgical resectability.

METHODS

We retrospectively reviewed the CT scans of 133 patients who underwent surgical resection for thymoma at our institution between July 21, 1997, and September 22, 2010. Imaging characteristics recorded included tumor size, attenuation, contact of mediastinal vessels, tumor morphology, infiltration of surrounding fat, changes in the adjacent lung parenchyma, lymphadenopathy, and pleural involvement.

RESULTS

The study group included 66 men and 67 women, aged 23-88 years (mean 58.8 years). Eighty patients (60.2%) were Masaoka stage I or II and 53 (39.8%) were Masaoka stage III or IV. Twenty-three patients (17.3%) had an incomplete surgical resection. Of these, 15 patients had microscopic residual disease (11.2%) and eight had gross residual disease (6.0%). The preoperative CT characteristics that correlated with an incomplete surgical resection included a lobulated tumor contour (p = 0.016), greater than or equal 50% abutment of the circumference of an adjacent vessel (p < 0.001), thoracic lymphadenopathy (p = 0.029), adjacent lung changes (p = 0.005) and pleural nodularity (p = 0.001). Tumor size was larger in the incompletely versus completely resected groups, with mean values of 9.7 and 6.9 cm (p value 0.013). On multivariate analysis, only degree of abutment of adjacent vessels and pleural nodularity were independent predictors of incomplete resection.

CONCLUSIONS

Preoperative CT findings can predict the likelihood of successful surgical resection and could help to identify patients who might benefit from neoadjuvant chemotherapy.

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.

FDG PET-CT aids in the preoperative assessment of patients with newly diagnosed thymic epithelial malignancies

INTRODUCTION

Advanced thymoma (stage III and IV) is difficult to detect by computed tomography (CT), yet it is important to distinguish between early (stage I and II) and advanced disease before surgery, as patients with locally advanced tumors require neoadjuvant chemotherapy to enable effective resection. This study assessed whether the amount of fluorodeoxyglucose (FDG) uptake can predict advanced thymoma and whether it can separate thymoma from thymic cancer.

METHODS

We retrospectively reviewed FDG positron emission tomography (PET)-CT scans of 51 consecutive newly diagnosed patients with thymic epithelial malignancy. PET-CT findings documented focal FDG activity: SUVmax, SUVmean, SUVpeak, and total body volumetric standardized uptake value (SUV) measurements. These were correlated with Masaoka-Koga staging and World Health Organization classification. Wilcoxon ranked sum tests were used to assess association between SUV and pathological stage, cancer type, and classification.

RESULTS

Among the study patients, 37 had thymoma, 12 thymic carcinoma, and 2 thymic carcinoid. Higher focal FDG uptake was seen in patients with type B3 thymoma than in those with type A, AB, B1, or B2 thymoma (p < 0.006). FDG uptake was higher in patients with thymic carcinoma or carcinoid than in patients with thymoma (p < 0.0003), with more variable associations with volumetric SUV measurements. There was no significant association observed between higher focal FDG uptake and advanced-stage disease in thymoma patients (p > 0.09), although greater FDG-avid tumor volume was significantly associated with advanced disease (p < 0.03).

CONCLUSIONS

Focal FDG uptake cannot predict advanced thymoma but is helpful in distinguishing thymoma from thymic carcinoma, or the more aggressive thymoma, type B3.

Establishment and characterization of a novel cell line derived from human thymoma AB tumor

Thymomas are low-grade epithelial tumors of the anterior mediastinum. The complexity of the disease and the lack of in vitro and in vivo models hamper the development of better therapeutics. In this study, we report a novel cell line, designated as IU-TAB-1, which was established from a patient with stage II thymoma (World Health Organization-type AB). The IU-TAB-1 cell line was established in vitro and characterized using histological and immunohistochemical staining, fluorescence-activated cell sorting, cytogenetic analyses and functional assays including in vitro and a NOD/SCID xenograft model. A whole-genome gene expression analysis (Illumina) was performed on the IU-TAB-1 cell line and 34 thymomas to determine the clinical relevance of the cell line. The IU-TAB-1 cell line was positive for epithelial markers (pan-cytokeratin and EpCAM/CD326) including thymic epithelial (TE) surface markers (such as CD29, CD9, CD54/ICAM-1, CD58 and CD24) and p63, and negative for B- and T-cell lineage markers. Gene expression profiling demonstrated overlapping and distinct genes between IU-TAB-1 and primary thymomas including the primary tumor (from which the cell line was derived). IU-TAB-1 cells are tumorigenic when implanted in immunodeficient mice with tumors reaching a volume of 1000 mm³ at around 130 days. The established cell line represents a biologically relevant new tool to investigate the molecular pathology of thymic malignancies and to evaluate the efficacy of novel therapeutics both in vitro and in vivo.

Molecular analysis of thymoma

Histologic classification of thymomas has significant limitations with respect to both subtype definitions and consistency. In order to better understand the biology of the disease processes, we performed whole genome gene expression analysis. RNA was extracted from fresh frozen tumors from 34 patients with thymomas and followup data was available. Using the Illumina BeadStudio® platform and Human Ref-8 Beadchip, gene expression data was analyzed with Partek Genomics Suite®, and Ingenuity Pathways Analysis (IPA). Unsupervised clustering of gene expression data, representing one of the largest series in literature, resulted in identification of four molecular clusters of tumors (C1–C4), which correlated with histology (P = 0.002). However, neither histology nor clusters correlated with clinical outcomes. Correlation of gene expression data with clinical data showed that a number of genes were associated with either advanced stage at diagnosis or development of recurrence or metastases. The top pathways associated with metastases were amino acid metabolisms, biosynthesis of steroids and glycosphingolipids, cell cycle checkpoint proteins and Notch signaling. The differential expression of some of the top genes related to both metastases and stage was confirmed by RT-PCR in all cases of metastases and matched nonmetastatic cases. A number of potential candidates for therapeutics were also identified.

Phase II study of belinostat in patients with recurrent or refractory advanced thymic epithelial tumors

PURPOSE

Thymic epithelial tumors are rare malignancies, and there is no standard treatment for patients with advanced disease in whom chemotherapy has failed. Antitumor activity of histone deacetylase (HDAC) inhibitors in this disease has been documented, including one patient with thymoma treated with the pan-HDAC inhibitor belinostat.

PATIENTS AND METHODS

Patients with advanced thymic epithelial malignancies in whom at least one line of platinum-containing chemotherapy had failed were eligible for this study. Other eligibility criteria included adequate organ function and good performance status. Belinostat was administered intravenously at 1 g/m(2) on days 1 to 5 of a 21-day cycle until disease progression or development of intolerance. The primary objective was response rate in patients with thymoma.

RESULTS

Of the 41 patients enrolled, 25 had thymoma, and 16 had thymic carcinoma; patients had a median of two previous systemic regimens (range, one to 10 regimens). Treatment was well tolerated, with nausea, vomiting, and fatigue being the most frequent adverse effects. Two patients achieved partial response (both had thymoma; response rate, 8%; 95% CI, 2.2% to 25%), 25 had stable disease, and 13 had progressive disease; there were no responses among patients with thymic carcinoma. Median times to progression and survival were 5.8 and 19.1 months, respectively. Survival of patients with thymoma was significantly longer than that of patients with thymic carcinoma (median not reached v 12.4 months; P = .001). Protein acetylation, regulatory T-cell numbers, and circulating angiogenic factors did not predict outcome.

CONCLUSION

Belinostat has modest antitumor activity in this group of heavily pretreated thymic malignancies. However, the duration of response and disease stabilization is intriguing, and additional testing of belinostat in this disease is warranted.

Imaging thymoma

Thymoma is a rare tumor, although it is the most common primary neoplasm of the anterior mediastinum. In the majority of thymoma patients, imaging is requested for investigation of symptoms related to their tumor, although an increasing number of asymptomatic patients are discovered incidentally due to the increased utilization of computed tomography for screening or for imaging of other unrelated diseases. This review will focus on the goals of imaging thymoma, the imaging features of thymoma, as well as the advantages and limitations of each imaging modality in establishing the diagnosis, staging, and prognosis of thymoma.

The autoimmune regulator AIRE in thymoma biology: autoimmunity and beyond

Thymomas are tumors of thymic epithelial cells. They associate more often than any other human tumors with various autoimmune diseases; myasthenia gravis is the commonest, occurring in 10-50% of thymoma patients, depending on the World Health Organization-defined histologic subtype. Most thymomas generate many polyclonal maturing T lymphocytes but in disorganized microenvironments Failure to induce self-tolerance may be a key factor leading to the export of potentially autoreactive CD4 progeny, thus predisposing to autoimmune diseases. Normally, the master Autoimmune Regulator promotes expression of peripheral tissue-restricted antigens such as insulin by medullary thymic epithelial cells and induction of tolerance to them. The failure of approximately 95% of thymomas to express autoimmune regulator is another feature potentially contributing to autoimmunity.

Thymoma and paraneoplastic myasthenia gravis

Paraneoplastic autoimmune diseases associate occasionally with small cell lung cancers and gynecologic tumors. However, myasthenia gravis (MG) occurs in at least 30% of all patients with thymomas (usually present at MG diagnosis). These epithelial neoplasms almost always have numerous admixed maturing polyclonal T cells (thymocytes). This thymopoiesis-and export of mature CD4(+)T cells-particularly associates with MG, though there are rare/puzzling exceptions in apparently pure epithelial WHO type A thymomas. Other features potentially leading to inefficient self-tolerance induction include defective epithelial expression of the autoimmune regulator (AIRE) gene and/or of major histocompatibility complex class II molecules in thymomas, absence of myoid cells, failure to generate FOXP3(+) regulatory T cells, and genetic polymorphisms affecting T-cell signaling. However, the strong focus on MG/neuromuscular targets remains unexplained and suggests some biased autoantigen expression, T-cell selection, or autoimmunization within thymomas. There must be further clues in the intriguing serological and cellular parallels in some patients with late-onset MG but without thymomas-and in others with AIRE mutations-and in the contrasts with early-onset MG, as discussed here.

World Health Organization classification of thymomas provides significant prognostic information for selected stage III patients: evidence from an international thymoma study group

Information regarding prognosis of thymoma patients stratified by both World Health Organization classification and Masaoka staging system is very limited. Analyze 5-year survival data from a large number of thymoma patients stratified by both World Health Organization histologic type and Masaoka stage using meta-analysis. Perform power analysis to estimate the number of cases that would be needed to test the null hypothesis to a power of 80%. Five-year survival data from 905 thymoma patients treated with thymectomy at seven hospitals in America, Japan, Korea, India, Italy, and Germany. Survival data was reported as "dead" or "alive" to facilitate meta-analysis. Significant differences were detected only when comparing survival rates of thymoma patients in stages I to III with those of stage IV disease. Analysis by World Health Organization histologic type and stage yielded significant differences only in patients with thymomas A vs. B2 and A vs. B3 in stage III disease. No significant data heterogeneity was detected with funnel plots and Egger's regression test. Power analysis estimated that a study with 7077 patients is needed to evaluate the prognostic significance of all thymomas stratified by both World Health Organization histologic type and stage to a power of 80%. Selected World Health Organization histologic types are significantly associated with prognosis in stage III thymoma patients and may help select individuals benefiting from neoadjuvant therapy. Power analysis shows that studies with much larger number of patients are needed to exclude the possibility that histologic type may provide significant prognostic information in other stages of the disease.

(18)F-FDG PET/CT is Useful for Pretreatment Assessment of the Histopathologic Type of Thymic Epithelial Tumors

PURPOSE

This study was performed to assess the usefulness of (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) or PET/computed tomography (CT) for distinguishing thymic epithelial tumors according to World Health Organization (WHO) classifications.

METHODS

We analyzed a total of 45 patients (range, 29-75 years of age; mean, 55 years) with pathologically confirmed thymic epithelial tumors who underwent pretreatment (18)F-FDG PET or PET/CT between November 2003 and October 2009. The size, visual grading of uptake value, peak standardized uptake value (SUVpeak), uptake pattern, and contour of each tumor, and associated findings on PET or PET/CT, were analyzed relative to the three simplified WHO subgroups: less-invasive thymomas (types A and AB), more-invasive thymomas (types B1, B2, and B3) and thymic carcinomas. We statistically assessed the relationship of (18)F-FDG PET or PET/CT findings with these simplified subgroups.

RESULTS

Of the 45 patients, ten had less-invasive thymomas, 23 had more-invasive thymomas, and 12 had thymic carcinomas. The SUVpeak of the less- and more-invasive thymomas were significantly lower than those of thymic carcinomas (p < 0.000), but there was no difference in SUVpeak between less- and more-invasive thymomas. The visual grading scale (p < 0.000), uptake pattern (p = 0.001), and contour (p < 0.000) of the tumors differed significantly among the three simplified subgroups.

CONCLUSION

The image findings of (18)F-FDG PET or PET/CT differed significantly by histologic subgroups. Pre-treatment evaluation with (18)F-FDG PET or PET/CT might be helpful in differentiating subgroups of thymic epithelial tumors.

Thymoma in children: report of 2 cases and review of the literature

Thymoma is an uncommon and slow-growing neoplasm. It is derived from thymic epithelial cells and comprises about 20% to 30% of mediastinal masses in adults, but only about 1% in pediatric patients. Patients usually present with mass-associated respiratory symptoms, superior vena cava syndrome, or paraneoplastic syndrome including myasthenia gravis, pure red cell aplasia, or acquired hypogammaglobulinemia, and connective tissue disorders. Due to the limited number of cases, knowledge, and experience with thymoma in pediatric patients, the diagnosis and treatment are very challenging for this age group. In this article, we report 2 cases of thymoma in childhood and provide a comprehensive review and analysis of the reported pediatric cases in the past 30 years (total of 32 cases). We found that patients younger than age 10 years were predominantly male (M:F = 6:1) and had advanced tumor stage more frequent than patients older than age 10 (P = .03). There were also significant associations of male sex with more advanced tumor stage and less favorable outcome (P = .03). These findings suggest that age and sex may be additional potential prognostic contributors in pediatric patients with thymoma. The clinicopathologic features, differential diagnosis, and current therapeutic recommendations of this uncommon tumor in pediatric patients are also addressed.