Thymic epithelial tumors: comparison of CT and MR imaging findings of low-risk thymomas, high-risk thymomas, and thymic carcinomas

OBJECTIVE: To assess the CT and magnetic resonance (MR) imaging findings of thymic epithelial tumors classified according to the current World Health Organization (WHO) histologic classification and to determine useful findings in differentiating the main subtypes. MATERIALS AND METHODS: Sixty patients with thymic epithelial tumor who underwent both CT and MR imaging were reviewed retrospectively. All cases were classified according to the 2004 WHO classification. The following findings were assessed in each case on both CT and MRI: size of tumor, contour, perimeter of capsule; homogeneity, presence of septum, hemorrhage, necrotic or cystic component within tumor; presence of mediastinal lymphadenopathy, pleural effusion, and great vessel invasion. These imaging characteristics of 30 low-risk thymomas (4 type A, 12 type AB, and 14 type B1), 18 high-risk thymomas (11 type B2 and seven type B3), and 12 thymic carcinomas on CT and MR imaging were compared using the chi-square test. Comparison between CT and MR findings was performed by using McNemar test. RESULTS: On both CT and MR imaging, thymic carcinomas were more likely to have irregular contours (P < .001), necrotic or cystic component (P < .05), heterogeneous contrast-enhancement (P < .05), lymphadenopathy (P < .0001), and great vessel invasion (P < .001) than low-risk and high-risk thymomas. On MR imaging, the findings of almost complete capsule, septum, and homogenous enhancement were more commonly seen in low-risk thymomas than high-risk thymomas and thymic carcinomas (P < .05). MR imaging was superior to CT in the depiction of capsule, septum, or hemorrhage within tumor (all comparison, P < .05). CONCLUSION: The presence of irregular contour, necrotic or cystic component, heterogeneous enhancement, lymphadenopathy, and great vessel invasion on CT or MR imaging are strongly suggestive of thymic carcinomas. On MR imaging, the findings of contour, capsule, septum, and homogenous enhancement are helpful in distinguishing low-risk thymomas from high-risk thymomas and thymic carcinomas.     

胸腺瘤的CT和平片分析

目的　探讨胸腺瘤的X线与CT诊断价值。方法　分析 30例经手术病理证实的胸腺瘤X线和CT表现 ,并与病理对照。结果　 18例非侵袭性胸腺瘤 ,胸片仅发现 15例 ,CT扫描 10例 ,均为前纵隔软组织肿块 ,边界清楚 ,密度均匀。 12例侵袭性胸腺瘤 ,肿瘤侵犯邻近器官 ,CT显示纵隔胸膜受侵 3例 ,心包受侵 2例 ,大血管结构受侵 2例 ,胸膜种植 3例 ,胸腔积液 2例 ,腹腔受侵和纵隔淋巴结转移各 1例 ;胸片仅能显示 1例肿瘤侵犯纵隔胸膜和 1例胸膜种植。结论　CT扫描在胸腺瘤的发现和判别侵袭性方面明显优于X线平片并且是可靠预测胸腺瘤侵袭性的检查方法。     

Computed tomography and magnetic resonance imaging of mediastinal tumors

We describe the clinical, pathological, and imaging findings of mediastinal tumors with focus on thymic hyperplasia, thymic epithelial tumors, and germ cell tumors, malignant lymphoma, and various cystic masses. Chemical shift magnetic resonance imaging (MRI) is useful in characterization of the normal thymus and differentiation of hyperplastic thymus and thymic tumors. In contrast to noninvasive thymomas, invasive thymomas and thymic carcinomas show a more aggressive growth pattern. Local invasion and pleural spread are characteristic of invasive thymoma and mediastinal lymphadenopathy and distant metastasis suggest thymic carcinomas. Mature teratoma typically shows various computed tomography (CT) attenuation, and MR signal intensity depending on its contents and fat tissue and bone within the lesions are its characteristic findings. Seminomas typically have homogenous internal CT attenuation and MR signal intensity with minimal contrast enhancement. Nonseminomatous malignant germ cell tumors characteristically show prominent internal degenerative changes and invasion to the adjacent structures. In mediastinal lymphomas, a residual mass is common after treatment and MRI provides important information in distinguishing viable tumors from residual benign masses. Some mediastinal cysts may reveal high attenuation similar to solid lesions on CT depending on their contents and MRI can be useful in the differentiation of cystic masses from solid lesions.     

侵袭性胸腺瘤的CT诊断及评价

目的分析侵袭性胸腺瘤的ＣＴ表现以便于分期和计划治疗。材料与方法分析２６例手术及病理证实的侵袭性胸腺瘤的ＣＴ所见，着重观察病变的密度，对周围纵隔结构的侵犯、胸膜种植以及纵隔外转移情况。结果２６例侵袭性胸腺瘤ＣＴ均显示为前纵隔软组织肿块，１６例密度不均，肿块不规则侵犯邻近器官２４例，主要表现在纵隔胸膜受侵７例，肺受侵９例，胸膜种植３例，心血管结构受侵２０例，以及心膈角区和腹腔受侵３例。结论ＣＴ在显示胸膜、心包和肺实质侵犯方面极其有效，对病变范围可进行可靠的评价，常规ＣＴ扫描可进行准确的分期和决定治疗方案。     

侵袭性胸腺瘤的CT表现及病理对照

目的：分析侵袭性胸腺瘤的CT表现，评价CT对其临床分期的准确性。资料与方法：回顾分析32例经手术病理证实的侵袭性胸腺瘤的CT所见，通过对病变的密度、周围纵隔结构的侵犯、胸膜肿植以及纵隔外转移情况的观察进行分期，并和病理分期进行比较。结果：侵袭性胸腺瘤的CT表现主要有：分叶状或不规则肿块；密度不均匀；局灶性钙化；邻近结构的脂肪层消失；侵及心包、胸膜、肺及其他器官。CT对临床分期判断准确性为87．5％，特异性为90％，敏感性为83．3％。结论：CT对侵袭性胸腺瘤术前分期及病变范围的显示准确，对确定手术方案，评价治疗效果及判断复发具有重要意义。     

Use of fluorine-18 fluorodeoxyglucose positron emission tomography in the detection of thymoma: A preliminary report

Thymomas are lacking in malignant cytological features. Their staging is defined by the invasiveness of the tumour. This study aimed to analyse the uptake patterns of fluorine-18 fluorodeoxyglucose (FDG) in thymomas of different stages. FDG positron emission tomography (PET) scan was performed in 12 patients suspected of having thymoma and in nine controls. Qualitative visual interpretation was used to detect the foci with FDG uptake higher than that of normal mediastinum. Tumour/lung ratio (TLR) was calculated from the counts of ROIs over the mass and over comparable normal lung tissue in thymoma patients. Mediastinum/lung ratio (MLR) was calculated from the counts of ROIs over the anterior mediastinum and lung in controls. The PET scan patterns of distribution of foci with FDG uptake and TLRs were correlated with the computed tomography (CT) or magnetic resonance imaging (MRI) findings, and staging of the thymomas. Thymectomy was performed in ten patients and thoracoscopy was done in two patients. The results revealed ten thymomas (two stage I tumours, two stage II, four stage III and two stage IV, according to the Masaoka classification), and two cases of thymic hyperplasia associated with myasthenia gravis. Myasthenia gravis was also noted in four thymoma patients. FDG studies showed (a) diffuse uptake in the widened anterior mediastinum in patients with thymic hyperplasia, (b) confined focal FDG uptake in the non-invasive or less invasive, stage I and II thymomas, and (c) multiple discrete foci of FDG uptake in the mediastinum and thoracic structures in stage III and IV advanced invasive thymomas. The thymomas had the highest TLRs, followed by the TLRs of thymic hyperplasia and the MLRs of control subjects (P <0.005). No significant difference was found between thymomas in different stages or between thymomas with and thymomas without myasthenia gravis. In comparison with CT and/or MRI, FDG-PET detected more lesions in patients with invasive thymomas and downgraded the staging of thymoma in four patients. Our preliminary results suggest that FDG-PET is useful in the assessment of the invasiveness of thymomas, and may have the potential to differentiate thymomas from thymic hyperplasia.     

CT扫描对侵袭性胸腺瘤的诊断价值

目的　探讨侵袭性胸腺瘤的CT表现及其诊断价值。方法　回顾性分析 13例经手术、病理证实为侵袭性胸腺瘤的CT表现。结果　 13例侵袭性胸腺瘤CT均显示为前纵隔软组织肿块。 10例密度不均 ,肿块不规则侵犯邻近结构 11例。主要表现在胸膜种植 3例 ,心血管结构侵犯 9例 ,以及腹腔受侵 1例。结论　常规CT扫描在侵袭性胸腺瘤的诊断与鉴别诊断中具有重要作用     

Thymic lesions and myasthenia gravis. Diagnosis based on mediastinal imaging and pathological findings

Purpose:
To achieve a better understanding of the role of CT and MR imaging in the study of the mediastinum in patients with myasthenia gravis (MG). Material and Methods:
Mediastinal CT and MR findings were correlated with the histopathological results in 104 thymectomized MG patients. Results:
CT was performed in 104 patients; in 11 of them, MR was also carried out. 44 patients had hyperplasia at histology. On CT, thymic hyperplasia was confirmed in 16 cases, thymoma was diagnosed in 10 and a normal thymus in 18 (sensitivity 36%, specificity 95%). Of 52 patients with thymoma at histology, CT showed thymoma in 46, hyperplasia in 1, and normal thymus in 5. CT showed 88.5% sensitivity and 77% specificity for thymoma. In 10 patients with invasive thymoma, CT was indiscriminate, while invasiveness was detected in 7 cases at MR (70% sensitivity) and at CT in 1 case. Both CT and MR detected tumor recurrence in 5 cases, but the exact localization and degree of invasion were best defined by MR. Conclusion:
In MG patients CT is a sensitive, specific and efficient modality for detecting thymoma, but is less so for detecting thymic hyperplasia. MR was shown to be accurate in detecting invasive thymoma both preoperatively and in postoperative follow-up.     

MR imaging in the management of thoracic malignancies

CT remains the modality of choice for evaluating patients with a thoracic malignancy. In specific cases MR imaging can provide useful information that cannot be obtained with CT, and thus is useful as a problem solving tool. Advantages of MR imaging include superb demonstration of vessels and vessel/mass relationships, direct multiplanar imaging capability, and the potential for tissue characterization. MR imaging is useful in staging the patient with lung cancer when vascular or mediastinal invasion is in question. Its specific applications in surgical planning include the question of chest wall invasion, brachial plexus involvement, and transgression of the diaphragm, pericardium, or lung apex. Multiplanar imaging is useful in radiation therapy planning, displaying lesion extent in a coronal or sagittal format rather than on multiple axial images. Multiplanar capability also resolves problem areas for CT such as the aortopulmonic window, subcarinal region, and lesions at the cervicothoracic or thoracoabdominal junction. Structures such as the trachea and superior vena cava can be evaluated in their plane of anatomic orientation. Routine spin-echo and fast (GRASS) imaging of mediastinal vessels is useful in the evaluation of venous thrombosis as a result of catheters or tumors. The diagnosis and follow-up are obtained without the use of intravenous contrast material or radiation. When CT cannot evaluate vessels adequately because of surgical clip artifacts or postoperative distortion of anatomy, MR imaging is useful in the determination of vessel patency as well as identification of tumor recurrence. Cardiac masses are very well demonstrated by MR imaging. A unique feature of MR imaging is its potential for tissue characterization and ability to assess disease activity. Lymphoma evaluation is an active area of research. MR imaging can evaluate the radiated patient for tumor response and recurrence. Fibrous tissue remains of low signal intensity on T2-weighted images, whereas tumor has increased signal intensity. MR imaging may detect tumor recurrence before an increase in the size of a residual lymphoma mass and before clinical recurrence is evident. The area of increased signal can also serve as a guide to the appropriate site for biopsy to confirm recurrence. In addition, MR imaging can help characterize some adrenal and liver masses, potentially helping to avoid more invasive diagnostic procedures. At the current time MR spectroscopy does not have a clinical role in thoracic malignancies, but it may be a powerful tool in the future for diagnosis and management.     

Invasive and noninvasive thymoma: distinctive CT features

PURPOSE: The purpose of this work was to evaluate the CT features of thymoma and to determine the most helpful findings in differentiating invasive from noninvasive thymoma. METHOD: The CT scans from 27 patients with invasive thymoma and 23 with noninvasive thymoma were independently assessed by two observers without knowledge of their invasiveness. The presence and distribution of various CT findings were independently analyzed. RESULTS: Invasive thymomas were more likely to have lobulated (16/27, 59%) or irregular (6/27, 22%) contours than noninvasive thymomas (8/23, 35% and 1.5/23, 6%, respectively) (p < 0.05). Invasive thymomas had a higher prevalence of low attenuation areas within the tumor (16/27, 60%) than noninvasive thymomas (5/23, 22%) (p < 0.001) as well as foci of calcification (14.5/27, 54% vs. 6/23, 26%; p < 0.01). CONCLUSION: The presence of lobulated or irregular contour, areas of low attenuation, and multifocal calcification is suggestive of invasive thymoma.     

恶性胸腺瘤的CT与MRI诊断

目的：分析侵袭性胸腺瘤及胸腺癌的CT及MRI表现，探讨其鉴别诊断要点。方法：复习经病理组织学证实的18例侵袭性胸腺瘤及9例胸腺癌的CT、MRI所见，重点观察肿瘤的大小、密度、边缘改变，对周围纵隔结构的侵犯。结果：18例侵袭性胸腺瘤、9例胸腺癌CT、MRI均表现为前纵隔不规则软组织肿块。前者肿瘤直径大于8cm者15例（83％），病灶内密度及信号不均匀12例。心血管受侵16例，后者肿块直径在8cm以上者7例（77.8％),肿块内密度及信号不均6例，心知管受累8例，纵隔肺门淋巴结转移1例，肺内转移3例，双侧肾上腺及肝脏转移1例。结论：虽然侵袭性胸腺瘤和胸腺癌的影像学表现相似，但胸腺癌更具有侵袭性，胸外转移常见，病理组织学检查有助于两者的鉴别。     

Malignant thymic epithelial tumors: CT-pathologic correlation

OBJECTIVE: The purpose of our study was to describe and compare the CT and pathologic findings of atypical thymoma and thymic carcinoma. MATERIALS AND METHODS: Twenty-seven consecutive patients (14 men, 13 women ranging in age from 22 to 77 years [mean age, 52 years]) with pathologically proven atypical thymoma (n = 9) and thymic carcinoma (n = 18) constituted the study population. The chest CT findings in each of the 27 patients were reviewed retrospectively in consensus by two chest radiologists. These findings were correlated with pathologic findings. RESULTS: The tumors were located in the anterior mediastinum, and most tumors had a lobulated margin (24/27, 89%). Atypical thymomas were significantly smaller (mean, 4.7 cm) than thymic carcinomas (mean, 7.2 cm) (p = 0.041) on CT. The findings of invasion of the great vessels, lymph node enlargement, extrathymic metastases, and phrenic nerve palsy were seen only in patients with thymic carcinoma. The frequencies of necrosis, intratumoral calcification, pleural effusion, pleural implants, pericardial effusion, and obliteration of the mediastinal fat plane were not significantly different between atypical thymomas and thymic carcinomas (p > 0.05). Various histologic subtypes were included in thymic carcinoma. The tumor necrosis and calcification seen on CT were confirmed at pathologic examination. CONCLUSION: When a large thymic tumor appears with invasion of the great vessels, lymph node enlargement, phrenic nerve palsy, or extrathymic metastases on CT, thymic carcinoma rather than atypical thymoma should be considered.     

Differential diagnosis between thymoma and non-thymoma by dynamic MR imaging

Purpose:
To evaluate the usefulness of dynamic MR imaging for differential diagnosis of anterior mediastinal tumors. Material and Methods:
Fifty-nine patients with anterior mediastinal tumors were examined. According to histological diagnosis confirmed by surgery or biopsy, 31 had thymomas and 28 had non-thymoma lesions. The patients underwent dynamic MR imaging with gadopentetate dimeglumine administered as a bolus injection. Sequential images were obtained at 30-s intervals for 5 min. Significant differences in the mean peak times of time intensity curves (TICs) were found by histological type, using the Mann-Whitney test. Results:
The mean peak time of the TIC was 1.5 min in thymoma and 3.2 min in non-thymoma cases. The difference was statistically significant. Stages I and II of thymoma showed a mean value of 1.3 min, which was significantly shorter than that of 2.5 min in stage III. Differentiation of thymoma/non-thymoma based on the peak time of dynamic MR imaging showed optimal sensitivity (79%) and specificity (84%) when defining thymomas as lesions having peak time appearing earlier than 2 min and non-thymomas later than 2.5 min, with an accuracy of 81%. Conclusion:
Dynamic MR imaging may improve the differential diagnosis between thymoma and non-thymoma and the staging of thymoma.     

A potential pitfall of MR imaging for assessing mandibular invasion of squamous cell carcinoma in the oral cavity

BACKGROUND AND PURPOSE: Whether MR imaging is superior to CT in evaluating the presence and extent of mandibular invasion by squamous cell carcinoma remains controversial. The purpose of this study was to directly compare the diagnostic accuracy of MR imaging and that of CT. METHODS: MR and CT images in 51 patients with squamous cell carcinoma of the oral cavity were evaluated for the presence and extent of mandibular invasion. The results were correlated with histopathologic findings. RESULTS: Twenty-five of 51 patients had histopathologic evidence of mandibular cortical invasion. The tumor involved both the cortex and the bone marrow in all 25 patients and involved the inferior alveolar canal in 5 patients. The sensitivity and specificity for mandibular cortical invasion were 96% and 54% for MR imaging and 100% and 88% for CT, respectively. Those for inferior alveolar canal involvement were 100% and 70% for MR imaging and 100% and 96% for CT, respectively. In both evaluations, the specificity of MR imaging was significantly lower than that of CT (McNemar test, P = .004 in the former and P = .002 in the latter). Chemical shift artifact by bone marrow fat was postulated to be the source of most false-positive cases on MR imaging findings for mandibular cortical invasion. Those for inferior alveolar canal involvement were due to MR imaging visualization of the tumor and surrounding inflammation with similar signal intensity. CONCLUSION: In assessing the presence and extent of mandibular invasion by squamous cell carcinoma, the specificity of MR imaging was significantly lower than that of CT.     

Computed tomography and thymoma: distinctive findings in invasive and noninvasive thymoma and predictive features of recurrence

Purpose

Our goal was to assess the computed tomo graphy (CT) imaging findings of thymoma and to correlate these features with Masaoka staging system and prognosis.

Materials and methods

CT findings of thymoma were analysed in 58 patients who had undergone surgery between January 2002 and September 2007. All cases were classified according to the Masaoka staging system. The presence of various CT findings was correlated with tumour invasiveness and recurrence. In statistical analysis, a p value <0.05 was interpreted as significant.

Results

The study found 26 noninvasive thymomas and 32 invasive thymomas. Invasive thymomas were more likely to be greater in size (p<0.01), with lobulated or irregular contours (p<0.02), a necrotic or cystic component (p<0.04), foci of calcification (p<0.05) and heterogeneous contrast enhancement (p<0.01) than were noninvasive thymomas. Disease progression developed in nine of 58 patients. Tumour recurrence and metastasis correlated with greater size (p<0.04), lobulated or irregular contours (p<0.01), complete mediastinal fat obliteration (p<0.01), great vessel invasion (p<0.01) and pleural implants (p<0.02).

Conclusions

CT is useful in differentiating invasive from noninvasive thymomas and plays an important role in evaluating and treating these patients for multimodal therapy with neoadjuvant approaches. Moreover, CT findings may serve as predictors of postoperative recurrence or metastasis.     

MR imaging of the thymoma--differentiation of invasive thymoma from noninvasive thymoma

Magnetic resonance imaging (MRI) findings were reviewed in nine patients with histologically confirmed thymoma. The morphologic findings obtained by MRI were useful in distinguishing invasive from noninvasive thymoma. Invasive thymomas (2 cases) showed irregular contours and broad obliteration of the fatty plane between the mass and great vessels on T1-weighted coronary images. Perivascular infiltration shadow was considered to be characteristic of invasive thymoma. Noninvasive thymomas (7 cases) were round or oval in shape and showed slight obliteration of the fatty plane. In conclusion, MRI was helpful in differentiating invasive from noninvasive thymoma and defining the extent of thymoma.     

Adenocarcinoma of the pancreatic ducts: comparative evaluation with CT and MR imaging at 1.5 T.

A prospective comparison of computed tomography (CT) and magnetic resonance (MR) imaging at 1.5 T was performed in 50 patients with the suspected diagnosis of pancreatic carcinoma. CT scans were obtained before and after administration of contrast material in 41 of 50 patients (82%); 34 of 41 postcontrast scans (83%) were obtained with dynamic CT. MR images were interpreted without knowledge of the results of CT, ultrasound, cholangiography, or endoscopic retrograde cholangiopancreatography in 48 patients (96%). Surgical correlation of findings at CT and MR imaging was performed in 24 patients (48%) at laparotomy and in two patients (4%) at autopsy. On T1-weighted MR images, relatively diminished signal intensity of tumor compared with that of the adjacent pancreas was a consistent finding. MR imaging proved superior to CT in identification of pancreatic carcinoma (particularly in smaller intrapancreatic tumors), peripancreatic extension, vascular and portal vein invasion, and duodenal invasion. These results suggest that MR imaging of the pancreas is superior in many instances to CT in preoperative evaluation of pancreatic carcinoma.     

Thymic hyperplasia and thymus gland tumors: differentiation with chemical shift MR imaging

PURPOSE: To prospectively evaluate chemical shift magnetic resonance (MR) imaging for differentiating thymic hyperplasia from tumors of the thymus gland. MATERIALS AND METHODS: The institutional review board approved this study; informed consent was obtained and patient confidentiality was protected. The authors assessed 41 patients (17 male, 24 female; age range, 16-78 years) in whom thymic lesions were seen at chest computed tomography. Patients were assigned to a hyperplasia group (n=23) (18 patients with hyperplastic thymus associated with Graves disease and five with rebound thymic hyperplasia) and a tumor group (n=18) (seven patients with thymomas, four with invasive thymomas, five with thymic cancers, and two with malignant lymphomas). T2-weighted fast spin-echo and T1-weighted in-phase and opposed-phase MR images were obtained in all patients and visually assessed. A chemical shift ratio (CSR), determined by comparing the signal intensity of the thymus gland with that of the paraspinal muscle, was calculated for quantitative analysis. Mean CSRs for the patient groups and subgroups were analyzed by using Welch t and Newman-Keuls tests. P<.05 indicated a significant difference. RESULTS: The thymus gland had homogeneous signal intensity in all 23 patients in the hyperplasia group and in 12 of the 18 patients in the tumor group. The mean CSR (+/- standard deviation) was 0.614 +/- 0.130 in the hyperplasia group and 1.026 +/- 0.039 in the tumor group. Mean CSRs in the patients with a hyperplastic thymus and Graves disease, rebound thymic hyperplasia, thymoma, invasive thymoma, thymic cancer, and malignant lymphoma were 0.594 +/- 0.120, 0.688 +/- 0.154, 1.033 +/- 0.043, 1.036 +/- 0.040, 1.020 +/- 0.044, and 0.997 +/- 0.010, respectively. The difference in CSR between the hyperplasia and tumor groups was significant (P<.001). Mean CSRs in the hyperplasia subgroups were lower than those in the tumor subgroups (P<.001). All hyperplasia group patients had an apparent decrease in thymus gland signal intensity at chemical shift MR imaging; no tumor group patients had a decrease in thymus gland signal intensity. CONCLUSION: Chemical shift MR imaging can be used to differentiate thymic hyperplasia from thymic tumors.     

Thymoma: radiologic-pathologic correlation.

Thymoma is the most common primary neoplasm of the thymus. The majority of thymomas are encapsulated masses and exhibit a benign behavior. Less frequently, thymomas may be locally invasive, or rarely they may metastasize to distant sites. The usual clinical presentation is that of an anterior mediastinal mass found incidentally in an asymptomatic patient. The variable gross features of thymoma and the potential for local invasion result in a variety of radiologic appearances. The most common radiologic manifestation is a rounded, soft-tissue mass of the anterior superior mediastinum. Computed tomography and magnetic resonance imaging typically show a prevascular mediastinal mass of variable size and may be helpful in the evaluation of adjacent structures in cases of invasive thymoma. The treatment of choice is complete surgical excision. Radiation therapy and chemotherapy may be used adjunctively to surgery in the treatment of invasive tumors. The prognosis of encapsulated thymoma is generally favorable. Invasive tumors are associated with a worse prognosis but may respond to radical resection.     

MSCT对胸腺上皮肿瘤WHO简化病理分型的鉴别诊断价值

目的探讨多层螺旋CT(MSCT)对低危型、高危型胸腺瘤及胸腺癌的鉴别诊断价值。方法回顾性分析经病理(穿刺或手术)证实的67例胸腺上皮肿瘤,基于WHO病理分型简化为低危型胸腺瘤、高危型胸腺瘤及胸腺癌三组,并对其CT征象进行统计分析。结果67例TETs中,低危型胸腺瘤30例(A型3例、AB型20例、B1型7例),高危型胸腺瘤22例(B2型11例、B3型11例),胸腺癌15例。高危型胸腺瘤、胸腺癌较低危型胸腺瘤易表现为边缘分叶或不规则(P均<0.05)及易出现对心包侵犯(P均<0.05);胸腺癌较低危型胸腺瘤易出现增强后密度不均、囊变坏死及胸膜转移(P均≤0.003);胸腺癌较低危型、高危型胸腺瘤易出现纵隔淋巴结肿大(P均≤0.002);纵隔大血管侵犯在三组间两两比较均有统计学差异(P均<0.05)。结论MSCT对TETs的WHO简化病理分型鉴别诊断具有重要价值。