Exploring the incidence rate and imaging differential diagnosis of anterior mediastinal lesions: an 11-year retrospective study based on 2,626 cases

Introduction

There are various low incidence mediastinal diseases, with most of them being located in the anterior mediastinum. Primary tumors of the anterior mediastinum include thymic epithelial tumors (TETs), lymphomas, germ cell tumors, and other mesenchymal tumors. They often have non-specific clinical manifestations, with smaller lesions being asymptomatic or mild and usually detected during physical examinations (1). Contrastingly, relatively large tumors often cause compression symptoms, including coughing, chest pain, and breathing difficulties (1).

Currently, more diagnostic techniques are gradually being implemented to diagnose mediastinal tumors. Bakan et al. (2) found that computed tomography (CT) perfusion scanning helps to distinguish thymoma from thymic hyperplasia, lymphoma, thymic cancer, and mediastinal lung cancer. Magnetic resonance imaging (MRI) has a certain value in the diagnosis of chest diseases. Hu et al. (3) used T2 sequence and diffusion imaging to detect collagen fiber typing within tumors to differentiate thymoma, thymic carcinoma, and lymphoma. Shen et al. (4) found that using dynamic contrast-enhanced MRI-derived parameters to distinguish thymic cancer from thymic lymphoma can improve diagnostic performance. The application of artificial intelligence machine learning and deep learning has gradually gained popularity in the study of mediastinal lesions. Feng et al. (5) established 14 machine learning models for predicting the risk classification of TETs.

However, the most convenient, inexpensive, and widely used examination technique in clinical practice is still CT examination, which can observe the lesions and their adjacent structures (6). Based on CT imaging features, a possible diagnosis can be made before surgery to assist further clinical treatment. With the improvement of low-dose chest screening coverage, the detection rate of mediastinal tumors is also increasing. Simultaneously, we have found that there are various types of anterior mediastinal lesions that exceed past knowledge. Since the release of the fifth edition of the World Health Organization (WHO) classification of chest tumors in 2021 (7), there has been no research to update the types and incidence rate of various primary tumors in the anterior mediastinum, nor has there been a systematic summary of the imaging differential diagnosis of different lesions in the anterior mediastinum, which would limit our clinical diagnosis.

This 11-year retrospective study aimed to systematically review and summarize cases of anterior mediastinal diseases as well as the incidence of different types of anterior mediastinal lesions. We hypothesized that age is a risk factor for developing anterior mediastinal lesions, with TETs being the most common type among these lesions. This study could help to further elucidate the characteristics of anterior mediastinal tumors and inform comprehensive diagnostic strategies with improved accuracy that facilitate clinical treatment. We present this article in accordance with the STROBE reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-13/rc).

Methods

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of Cancer Hospital, Chinese Academy of Medical Sciences (No. NCC4196) and the requirement for individual consent for this retrospective analysis was waived.

Patients

We retrospectively included patients with anterior mediastinal masses who underwent treatment at our hospital (Cancer Hospital, Chinese Academy of Medical Sciences) between January 2012 and December 2022. The inclusion criteria were as follows: (I) CT scan showing an anterior mediastinal lesion, with those extending to other mediastinal areas being included based on their maximum cross-sectional center point position [according to the International Thymic Malignancy Interest Group Standard (8)]; (II) initial diagnosis without prior treatment or surgery before the imaging examination; and (III) definitive histological classification determined through surgical or CT-guided biopsy specimen. The exclusion criteria were as follows: (I) patients without definitive pathological results; (II) patients with metastatic lymph nodes or mediastinal lung cancer; and (III) patients without clinical, imaging, or pathological data.

From January 2012 to December 2022, the total patient volume in our hospital was approximately 628,777. We included 2,626 patients with defined pathologies, 1,809 of whom had complete data regarding imaging and pathological characteristics for radiological diagnostic analysis (Figure 1). Among the 2,626 enrolled patients, there were 1,411 males and 1,215 females [median age 48.5 (interquartile range, 35–58) years].

Figure 1 Flowchart of the study population. Numbers in parentheses are the numbers of patients.

CT scanning protocol

All enrolled patients in our hospital underwent a similar scan and parameters setup but with different systems. The systems included Optima CT660, BrightSpeed CT, Revolution CT, and Discovery CT750 (all from GE Medical Systems, Milwaukee, WI, USA), and Toshiba Aquilion 64-slice spiral CT (Toshiba, Tokyo, Japan).

Analyses of clinical and radiological characteristics

We reviewed the clinical and radiological characteristics of the included patients. The clinical characteristics included age, sex, symptoms, smoking history, malignancy history, diagnostic method, tumor markers, and operation duration.

The CT characteristics included position, size, shape, edges, boundaries; the presence of cystic necrosis, calcification, and fat; average CT value, and enhancement features. Additionally, we reviewed the situation regarding surrounding tissue invasion, including the large vasculature, pericardium, pleura, and lungs. Finally, we reviewed the presence/absence of pericardial/pleural effusion, mediastinal lymph node enlargement, and distant metastasis.

The aforementioned CT characteristics were primarily derived from a report issued by our hospital. In case of any uncertainties, a senior radiologist with 27 years of experience in chest CT was consulted for the final decision.

Specific CT scan parameters and explanations for each variable are provided in Appendix 1.

Pathological analysis

Histological analyses were performed using tissue samples obtained during surgical resection or CT-guided biopsy. The tissue samples were fixed with neutral formalin fixative, followed by routine dehydration, paraffin embedding, and preparation of 4-μm thick sections for hematoxylin and eosin staining routine and immunohistochemical staining to confirm the diagnosis. Pathological diagnoses were primarily derived from reports issued by our hospital. If there were any uncertainties, senior pathologists specializing in chest pathology were consulted for the final diagnosis. Finally, the cases were grouped accordingly, and the histological classification was refined based on the histological sources of the WHO classification for chest tumors (7).

Statistical analysis

All statistical analyses were performed using the software SPSS 23.0 (IBM Corp., Armonk, NY, USA). Continuous variables with normal and non-normal distributions were represented as mean ± standard deviation and median (interquartile range), respectively. Classified data were presented as numbers (percentages). Independent sample t-tests and Mann-Whitney U-tests were used for categorical variables with normal and non-normal distributions, respectively. Variables with P<0.2 in the univariate logistic regression analysis were included in multivariate logistic regression analysis; additionally, the forward stepwise method was used to identify imaging and clinical features with predictive significance for differential diagnosis. A receiver operating characteristic (ROC) curve was drawn to analyze the predictive performance of various risk factors, with the AUC obtained to determine the predictive value of the identified factors. The maximum point of the Youden index was taken as the critical value to obtain sensitivity and specificity. The closer the AUC was to 1, the better the predictive performance of the indicator. Statistical significance was set at P<0.05. R language (V4.3.2; R Foundation for Statistical Computing, Vienna, Austria) was used to draw a nomogram chart that distinguished TETs and validated the clinical prediction model.

Results

Clinical characteristics

Among the enrolled patients, 1,508 (57.4%) were asymptomatic upon physical examination. The remaining 1,118 patients presented clinical symptoms such as chest pain, cough, chest tightness, breathing difficulty, limb fatigue, expectoration of phlegm and blood, fever, and facial or limb swelling, which accounted for 15.7%, 14.0%, 12.4%, 3.3%, 2.8%, 2.0%, and 2.2% of the patients, respectively. The incidence of dysphagia, hoarseness, dizziness, emaciation, pruritus, nausea, and palpitations was <1%. In our study, 78 patients had a history of malignant tumors, including lung, breast, and thyroid cancers (one patient had previously had colon and ovarian cancer). Ultimately, 1,672 and 954 patients were diagnosed through surgical and CT-guided biopsy specimens, respectively (Table 1).

Incidence of different pathological types of anterior mediastinal lesions

During the study period, around 2,626 patients with anterior mediastinal lesions initially visited our research center, representing an overall incidence of about 0.4%. The types of lesions included in this study are shown in Table 2 and Figure 2. Among them, TETs had the highest incidence, accounting for 56.1% of all anterior mediastinal lesions, with an incidence rate of approximately 0.2%. The second most common lesion was lymphoma, accounting for 16.3% of all anterior mediastinal lesions.

Figure 2 The prevalence of anterior mediastinal lesions in this study. (A) The proportion of various types of anterior mediastinal lesions. (B) The prevalence of anterior mediastinal lesions in different age groups. (C) The proportion of different histological types of TETs. TET, thymic epithelial-derived tumor.

Most included patients were aged 50–60 years (approximately 26.1%). TETs, including thymoma, thymic carcinoma, and neuroendocrine tumors, were most common among patients aged 50–60 years; lymphoma was the most common in patients aged 20–40 years; germ cell tumors, including teratomas, and other non-teratogenic germ cell tumors, such as seminoma and yolk sac tumors, were most common among patients aged 20–30 years; simple cysts, including thymic cysts and cysts, were most common among people aged 50–60 years; and the age distribution of other diseases varied widely.

Differential diagnosis between TETs and other malignant tumors

In this study, 1,809 patients had complete imaging information for analysis. There were 1,369 cases of malignant (n=1,002) and borderline (n=367) tumors, accounting for approximately 75.7% of the cases, including TETs and other malignant tumors, and these were divided into a training set (n=958) and a validation set (n=411) in a 7:3 ratio. Quantitative data, including age, average diameter, and CT value, were divided into four groups based on interquartile range.

In the training set, univariate and multivariate analyses indicated that age, average diameter, boundaries, calcification, average CT value, surrounding tissues invasion (vascular, pleural and lung), pericardial effusion, mediastinal enlargement of lymph nodes, and distant metastasis were statistically significant risk factors for distinguishing TETs from other malignant tumors (Table 3). The AUCs of the multivariate regression model for distinguishing TETs from other malignant tumors in the training and validation set were 0.94 [95% confidence interval (CI): 0.92–0.95] with a sensitivity of 81% and a specificity of 91%, and 0.93 (95% CI: 0.90–0.96) with a sensitivity of 78% and a specificity of 90%, respectively. The nomogram visualization of the prediction model is shown in the Figure 3. The ROC curves of the training and validation sets are shown in the Figure 4A, indicating that the predictive performance of the model was good. The calibration curve (Figure 4B) of the prediction model showed that the predicted results were close to the actual results, and the Hosmer-Lemeshow goodness of fit test results showed that there was no significant difference in fitting in the training set (P=0.687), validating that the predicted model results were consistent with the real ones.

Figure 3 Nomogram of clinical prediction model for TETs differential diagnosis. Univariate and multivariate logistic regression analysis were used for differential diagnosis of TETs. Calcification, boundary, vascular/pleural/lung invasion, pericardial effusion, mediastinal lymph node enlargement, distant metastasis, as well as age, mean diameter, CT values, together constituted the clinical prediction model, and a nomogram was drawn to visualize the prediction model. It could be seen that age was the most important predictive factor, with TETs mostly occurring in the middle-aged and elderly population. CT, computed tomography; TET, thymic epithelial-derived tumor.

Figure 4 The ROC curves and the calibration curve of the model. (A) The ROC curves of the training and validation sets were shown. The AUC of the multivariate regression model for distinguishing TETs from other malignant tumors in the training and validation sets were 0.94 (95% CI: 0.92–0.95) with a sensitivity of 81% and a specificity of 91%, and 0.93 (95% CI: 0.90–0.96) with a sensitivity of 78% and a specificity of 90%, respectively. (B) The calibration curve of the prediction model showed that the predicted results are close to the actual results, and the Hosmer-Lemeshow goodness of fit test results show that there was no significant difference in fitting in the training set (P=0.687), verifying that the predicted model results were consistent with the real ones. AUC, area under the curve; CI, confidence interval; ROC, receiver operating characteristic.

Imaging manifestations of other malignant lesions in the anterior mediastinum

Other malignant tumors with complete imaging data included lymphomas, malignant germ cell tumors, hematolymphoid tumors, and malignant mesenchymal tumors. Table 4 shows the CT imaging features of the aforementioned tumors. Malignant tumors were often large and irregular in shape, with rough edges, blurred boundaries, frequent necrosis, invasion of surrounding tissues, and frequent pericardial and pleural effusions (Figure 5). Regarding lymphomas, the manifestations included crossing mediastinal zones, mediastinal lymph node enlargement, invasion of surrounding tissues, and pericardial/pleural effusion, accounting for 26.3% (68/259), 65.6% (170/259), 88.0% (228/259), and 74.5% (193/259) of the cases, respectively. Among the malignant germ cell tumors, 16.9% (14/83) showed calcification and 4.8% (4/83) showed adipose tissue, which are both manifestations of malignant teratoma. Among malignant mesenchymal tumors, five cases of solitary fibromas and one each of T-lymphocytic lymphoma, mixed germ cell tumor, rhabdomyosarcoma, undifferentiated liposarcoma, and plasma cell tumor exhibited pronounced enhancement. Only patients with malignant teratoma (four cases) and liposarcoma (one case) contained fatty components. Other tumors were rare and showed atypical imaging manifestations, which impeded their differential diagnoses.

Figure 5 CT imaging findings of main malignant tumors in the anterior mediastinum. (A) AB type thymoma. A 61-year-old female was found to have a mass in the anterior mediastinum during physical examination. The size of the tumor is about 6.6 cm × 5.9 cm, with necrosis and vascular shadows visible inside. The edges are relatively smooth and the boundaries are clear. Uneven enhancement scan with moderate enhancement. (B) Thymic cancer. A 61-year-old male was found to have a mass in the anterior mediastinum during physical examination. The size of the tumor is approximately 8.5 cm × 7.9 cm, with necrosis and calcification visible inside. The edges are rough and divided into leaves, with unclear boundaries and involving the pericardium. Uneven enhancement scan with moderate enhancement. (C) Primary mediastinal large B-cell lymphoma. A 32-year-old male was found to have a mass in the left anterior mediastinum after presenting due to coughing. The size of the tumor is about 13.1 cm × 9.5 cm, with a small amount of necrosis visible inside. The edges are blurry, the boundaries are unclear, and they cross the longitudinal partition. Encapsulation and invasion of blood vessels, invasion of pericardium, pleura, and lung tissue. The enhanced scan shows moderate enhancement. Multiple enlarged lymph nodes are present in the mediastinum. Left pleural effusion. (D) Malignant mixed germ cell tumor. A 16-year-old male underwent physical examination for a mass in the right anterior mediastinum. The size of the tumor is about 11 cm × 6.2 cm, with necrosis visible inside. Blurred edges, unclear boundaries, invasion of pericardium, pleura, and lungs. Enhanced scanning shows uneven enhancement. Right pleural effusion. (E) Solitary fibrous tumor. A 60-year-old female underwent physical examination for a mass in the right anterior mediastinum. The size of the tumor is about 7.6 cm × 4.5 cm, with large cystic necrosis visible inside. Smooth edges and clear boundaries. Enhanced scanning shows significant uneven enhancement. (F) Liposarcoma. A 44-year-old female developed a right anterior mediastinal mass due to shortness of breath. The size of the tumor is approximately 10.9 cm × 8.8 cm, with cystic changes visible inside. The edges are rough, the boundaries are still clear, and the pericardium is affected. Enhanced scanning of solid components with moderate enhancement of nodules. CT, computed tomography.

Predictive value of risk stratification for TETs

We further divided the TETs into two groups: low-risk (A, AB, and B1 type thymomas, n=327) and high-risk (B2 and B3 types, thymic cancer, and neuroendocrine tumors, n=675) groups. There were significant differences in gender, average diameter, mediastinal cross-zone, margin, boundary, morphology, average CT value, invasion of surrounding tissues, mediastinal lymph node enlargement, and distant metastasis (P<0.05). Univariate and multivariate analyses revealed statistically significant differences in the average diameter, edges, boundaries, average CT value, surrounding tissue invasion (vascular, pericardium, and pleura), and mediastinal lymph node enlargement, which could be considered as risk stratification factors for TETs (Table 5). The AUC of the risk stratification multi-factor model for TETs was 0.865 (95% CI: 0.842–0.888), with a sensitivity of 72.0% and a specificity of 85.6% (Figure 6). These findings indicated that CT imaging features had a relatively high value in risk stratification of TETs.

Figure 6 Univariate and multivariate logistic regression analysis was used to the risk stratification of TETs. The average diameter, margin, boundary, average CT value, vascular, pericardial and pleural invasion, and mediastinal lymph node enlargement had statistical significance and could be considered as factors for risk stratification of TETs. The AUC of the ROC curve was 0.865 (95% CI: 0.842–0.888), with a sensitivity of 72.0% and a specificity of 85.6%. AUC, area under the curve; CI, confidence interval; CT, computed tomography; ROC, receiver operating characteristic; TET, thymic epithelial-derived tumor.

Imaging characteristics of benign lesions in the anterior mediastinum

This study included 440 cases of benign lesions with complete imaging data, including mature teratomas, simple cysts, mesenchymal tumors (schwannomas, hemangiomas, and lipomas), thymic tissue/hyperplasia, giant lymph node hyperplasia, inflammation, substernal goiter, lymphangioma, plasma cell hyperplasia, parathyroid adenoma, and hamartoma. The CT features of these aforementioned lesions were diverse (Table 6, Figure 7). Calcification was observed in 75% (3/4) of retrosternal goiters, 48.5% (50/103) of mature teratomas, 33.3% (1/3) of lipomas, 30.0% (3/10) of giant lymph node hyperplasias, 20.0% (1/5) of hemangiomas, and 6.6% (19/286) of simple cysts. Moreover, 66.7% (2/3) of lipomas and 63.1% (65/103) of mature teratomas had fatty components. There was significant enhancement in the arterial phase of contrast-enhanced scanning in 80.0% (4/5) of hemangiomas, 80.0% (8/10) of giant lymph node hyperplasias, 50.0% (2/4) of retrosternal goiters, and one parathyroid adenoma. Given the varying degrees of enhancement of different components within mature teratomas, there were diverse presentations of no, mild, medium, and high enhancements.

Figure 7 CT imaging findings of main benign lesions in the anterior mediastinum. (A) Thymic cyst. A 51-year-old male was found to have a mass in the anterior mediastinum due to coughing. The tumor is oval in shape, with a size of approximately 3.4 cm × 2.3 cm. The tumor has a liquid density and is not enhanced by enhanced scanning. Smooth edges and clear boundaries. (B) Mature teratoma. A 25-year-old male was found to have a mass in the right anterior mediastinum during physical examination. The size of the tumor is about 7.7 cm × 6.5 cm, with mature fat components and calcification visible inside. Smooth edges and clear boundaries. Enhanced scanning shows mild enhancement of the cyst wall. (C) Giant lymph node hyperplasia. An 18-year-old male was found to have a mass in the right anterior mediastinum due to cough and chest pain during examination. The size of the tumor is about 8.8 cm × 5.9 cm, with cystic necrosis and calcification visible inside. The edges are slightly blurry, and the boundaries are still clear. Enhanced scanning shows significant enhancement. (D) Mediastinal inflammation. A 30-year-old male was found to have a mass in the right anterior mediastinum due to chest pain examination. The size of the tumor is about 9 cm × 4 cm, with cystic necrosis visible inside. Blurred edges, unclear boundaries, and involvement of the pericardium. Enhanced scanning shows moderate enhancement. (E) Retrosternal goiter. A 62-year-old female was found to have a mass in the anterior mediastinum during physical examination. The size of the tumor is about 6 cm × 4.2 cm, with cystic necrosis and calcification visible inside. Smooth edges and clear boundaries. Enhanced scanning shows significant enhancement, consistent with thyroid tissue. (F) Hemangioma. A 44-year-old female was diagnosed with a right anterior mediastinal mass due to coughing. The size of the tumor is approximately 8.9 cm × 4.9 cm, with cystic changes visible inside. Blurred edges and unclear boundaries. Enhanced scanning revealed obvious enhancement nodules inside. CT, computed tomography.

Discussion

Since 2021, no study has been conducted to provide an up-to-date estimate of the incidence of various primary tumors in the anterior mediastinum, nor has any study summarized the imaging differential diagnosis of anterior mediastinal lesions. This study investigated the incidence of 2,626 cases of anterior mediastinal diseases and the imaging characteristics of 1,809 cases of major diseases from 2012 to 2022. We found that differential diagnosis of the various anterior mediastinal lesions could be facilitated by the clinical and imaging characteristics of the patients. Based on our findings, we developed a diagnostic strategy for invasive tumors in the anterior mediastinum (Figure 8), which could improve the accuracy of preoperative clinical diagnosis.

Figure 8 Diagnostic flowchart for anterior mediastinal lesions. The gray and black arrows represented the diagnostic process for anterior mediastinal tumors in teenagers/young people and middle aged/elderly people, respectively. Radiologists and clinical physicians can make preoperative diagnoses based on the patient’s age and imaging characteristics, and some laboratory indicators can also assist in diagnosis. AFP, alpha-fetoprotein; β-HCG, β human chorionic gonadotropin; HCG, human chorionic gonadotropin; LDH, lactate dehydrogenase; SFT, solitary fibrotic tumor; TC, thymic cancer; TET, thymic epithelial derived tumor.

We observed a very low incidence rate of anterior mediastinal lesions. Yoon et al. (9) reported that 0.7% of patients who underwent low-dose chest CT screening presented anterior mediastinal nodular lesions, with an expected incidence rate of 1% in the high-risk population aged 55–74 years. Further, the Framingham Heart Study and Early Lung Cancer Action Project (ELCAP) found that the incidence rate of anterior mediastinal masses was 0.9% and 0.5%, respectively (10,11). In this 11-year study, the incidence of mediastinal masses was around 0.4%, which is consistent with the results of the ELCAP study.

We believe that clinical diagnosis is made by radiographic imaging characteristics and confirmed with histological evaluation of surgical specimen/biopsy, which serves as the current gold standard. Our research mainly targeted radiologists, who hope to determine the nature of tumors preoperatively based on clinical characteristics other than symptoms (including gender, age, location, size), and preoperative CT imaging characteristics, and conducted systematic radiological diagnosis to guide physicians in the next step of treatment.

Age is an important factor to consider in the diagnosis of anterior mediastinal lesions. In the present study, anterior mediastinal lesions were most common in the age group of 40–60 years (approximately 47.2%), with TETs being the most common anterior mediastinal lesion. TETs were most common in middle-aged and elderly people (aged 50–60 years; approximately 56.1%); lymphomas were most common in individuals aged 20–40 years (approximately 16.3%); germ cell tumors were most common in young adults (20–30 years old); and simple cysts were most common in patients aged 50–60 years. These findings were consistent with those of previous studies (12-17). The remaining lesions were rare and showed no clear age tendency (18-22).

In clinical practice, surgery is the main treatment method for TETs, especially in low-risk patients, whereas advanced stages require a combination of radiotherapy and chemotherapy (23). Malignant germ cell tumors typically require a combination of chemotherapy and radiation therapy, whereas lymphoma and other malignant tumors typically require chemotherapy (24,25). Accordingly, differential diagnosis of malignant solid tumors in the anterior mediastinum is crucial for selecting treatment strategies. In our study, compared with other malignant tumors, TETs had a higher age of onset, smaller average diameter, higher density, fewer partitions across the mediastinum, rough edges but clearer boundaries, higher proneness to calcification, less invasion of surrounding tissues, mediastinal lymph node enlargement, and more distant metastases. These findings are consistent with those of previous studies (26-28). We constructed a clinical prediction model and plotted a nomogram. The AUCs for the training and validation sets were approximately 0.94 and 0.93, respectively.

The second most common malignant tumor was lymphoma. Lymphoma usually presents as a nodular fusion with a large tumor volume. In our study, lymphoma was more prone to peripheral tissue invasion, pleural/pericardial effusion, and mediastinal lymph node enlargement; these characteristics were present in 88.0%, 74.5%, and 65.6% of cases, respectively, which is consistent with previous findings (29). The third most common type was malignant germ cell tumors, except for typical malignant teratomas with calcification and fat. Other tumors, including seminoma and yolk sac tumors, were difficult to distinguish solely based on imaging features. Alpha-fetoprotein or beta-human chorionic gonadotropin are highly suggestive of the occurrence of this disease (30,31).

In our study, other malignant tumors had a low incidence rate and atypical imaging manifestations; accordingly, their definitive diagnosis still requires a puncture biopsy. Among malignant mesenchymal tumors, fibroblastic and myofibroblastic tumors, including solitary fibrotic tumors (SFTs), ligament fibromatosis, and fibrosarcoma, had a higher proportion. SFTs are relatively more common, with those occurring in the mediastinum or mediastinal lung junction often originating from the pleura and having a stronger malignant tendency (32). In our study, approximately 71.4% of SFTs showed rich blood supply, which are usually manifested as a “map-like” significant enhancement (33). Liposarcoma of the anterior mediastinum is rare, with pleomorphic liposarcoma being more common and often lacking mature adipose components (approximately 33.3% of liposarcomas) (34). In our study, lymphohematopoietic tumors, including myeloid sarcoma, granulocytic sarcoma, and plasma cell carcinoma, were sporadic. They have atypical imaging manifestations, with only a few previously reported cases (35-37).

Surgical resection is the primary treatment for Masaoka-Koga stage I or II TETs. For Masaoka-Koga stage III or IV TETs, preoperative or postoperative chemotherapy is initially administered, followed by further surgery or radiotherapy, based on the observed efficacy (38). CT features could also facilitate risk stratification of TETs to inform treatment. In our study, the average diameter, average CT value, edges, boundaries, invasion of surrounding tissues, and mediastinal lymph node enlargement were significant factors for risk stratification of TETs, which is consistent with previous reports (2,39-42). The AUC for the risk stratification model was 0.863, indicating that CT features are valuable for the risk stratification of TETs.

There are various benign lesions that may occur in the anterior mediastinum; cysts are the most common, including thymic, intestinal, and pericardial cysts. Given the bleeding and protein components inside cysts, they could have a higher density than normal water. In this study, there were some cysts with moderate wall enhancement and unclear boundaries, respectively, which could be attributed to infection or peripheral thymic epithelial hyperplasia. Mature teratomas are easier to diagnose due to their internal compositional characteristics. Cystic teratomas are prone to rupture, which leads to invasion of surrounding tissues (35.0% of cystic teratomas in our study) (43). Benign mesenchymal tumors were rare in the anterior mediastinum, with some of them showing atypical imaging characteristics. A significant enhancement of nodular shadow during the arterial phase of the enhanced scanning is suggestive of a vascular aneurysm. If mature fat is observed inside the tumor, it is important to consider the possibility of lipoma. Regular and smooth tumor bodies with more internal cystic changes may be differentiated from schwannomas. This was consistent with previous case reports (44-46).

This study has some limitations. First, this was a single-center retrospective study with a low incidence rate of some tumors, including hamartoma and parathyroid adenoma, and potential selection bias, limiting the generalizability of our findings. Second, our hospital only routinely performed arterial phase scans; however, thin-layer images are relatively reliable in evaluating features. Nonetheless, our findings may improve clinicians’ understanding of rare anterior mediastinal tumors. This is a preliminary study that requires further large-scale multicenter research combined with MRI and other examination methods.

Conclusions

Our results show several types of lesions in the anterior mediastinum, and the incidence rate is about 0.4%. In addition, age is associated with the occurrence of anterior mediastinal lesions. The incidence rate of TET was the highest (56.1%). We have constructed a clinical prediction model for TETs and plotted a nomogram, with a good predictive performance. By summarizing anterior mediastinal lesions, we can broaden our clinical understanding of anterior mediastinal injuries and consider more possibilities for preoperative imaging diagnosis based on this. A systematic diagnostic approach for anterior mediastinal lesions can be developed based on the clinical and imaging features reported herein.

Acknowledgments

We would like to acknowledge all our colleagues for their contribution to this research.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-13/rc

Funding: This work was supported by the Beijing Natural Science Foundation (grant No. 7222148), National Natural Science Foundation of China (grant No. 81971616), CAMS Innovation Fund for Medical Sciences (grant No. 2021-I2M-C&T-B-065), and the Special Research Fund for Central Universities, Peking Union Medical College (grant No. 3332022025).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-13/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of Cancer Hospital, Chinese Academy of Medical Sciences (No. NCC4196) and the requirement for individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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