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Introduction

Anterior mediastinal soft tissue chondromas are a rare subset of a broader category of soft tissue chondromas that arise from mature hyaline cartilage. Although these tumors are most commonly found in the extremities, they can occasionally occur in the mediastinum (1-3). A literature review conducted by Bansal et al (4) revealed that 96% of soft tissue chondromas occur in the extremities, with the majority of cases involving patients aged 30-60 years. The incidence rate is approximately equal between the sexes. These tumors are not attached to the cortex or periosteum of the adjacent bone, although they may originate from synovial tissue (4). Importantly, these generally benign tumors are often misdiagnosed due to their similarity in imaging characteristics to other more common anterior mediastinal masses (e.g., thymomas, teratomas and lymphomas) (5). Therefore, accurate diagnosis is critical for ensuring appropriate management, as the treatment approach for chondromas differs significantly from that taken for more aggressive or malignant mediastinal tumors (3,6). In this article, a rare case of chondroma located in the anterior mediastinum is presented. This case emphasizes the necessity of factoring in anterior mediastinal soft-tissue chondromas when differentiating calcified mediastinal masses. Comprehensive imaging assessment and histopathological analysis are crucial for an accurate diagnosis and appropriate management, thus preventing the overtreatment of benign lesions.

Case report

A 36-year-old Chinese female presented with an incidental finding of an anterior mediastinal mass during a routine health examination at a local hospital in June 2020. The patient was asymptomatic at the time of discovery, with no history of chest pain, dyspnea or other respiratory symptoms. Computed tomography (CT) revealed a lobulated, low-density mass measuring ~4.7x4.0 cm in the anterior mediastinum. Punctate calcifications were observed within the lesion and no significant enhancement was noted on contrast-enhanced imaging (Fig. 1A-E). The mass did not exhibit any signs of invasion into surrounding structures and there was no evidence of associated lymphadenopathy. Given the benign imaging characteristics, the patient underwent a median sternotomy for surgical resection of the mass. Intraoperatively, the tumor was well-encapsulated and easily separable from adjacent mediastinal structures (Fig. 1). The fully resected mass was confirmed the diagnosis of a soft tissue chondroma. The tumor was composed of mature hyaline cartilage with focal calcified areas and did not exhibit any signs of malignancy based on hematoxylin and eosin staining (Fig. 1F).

Figure 1 Contrast-enhanced chest CT imaging and histopathological examination. (A) Plain CT. (B) Arterial phase. (C) sagittal image of the venous phase.(D and E) coronal images of the venous phase. A well-circumscribed soft tissue mass is visible in the anterior mediastinum. Axial CT revealed a well-circumscribed calcified mass in the left anterior mediastinum. The mass was positioned anterior to the pulmonary trunk. Unenhanced CT showed near-isodense attenuation (15-22 HU). Minimal enhancement was observed (13-27 HU arterial phase; 14-27 HU venous phase). Additionally, there were no enlarged lymph nodes identified in the mediastinum. (F) The tumor consisted of mature hyaline cartilage cells and a rich chondroid matrix. The chondrocytes were arranged in clusters and resided within cartilage lacunae. The tumor was composed of mature hyaline cartilage with focal areas of calcification; features of malignancy were not observed (hematoxylin and eosin staining; scale bar, 200 µm). CT, computed tomography.

The postoperative recovery of the patient was uneventful and the patient was discharged in a stable condition. At the 6-month follow-up, the patient remained asymptomatic with no signs of recurrence on imaging examination, and further follow-up was arranged, but the patient was lost to follow-up.

Discussion

Chondromas can be classified into several types, including enchondroma, periosteal chondroma and multiple enchondromatosis. In addition to the aforementioned types, there is also a rare type known as soft tissue chondroma, also termed extraskeletal chondroma or chondroma of soft parts (7). Soft tissue chondroma represents a rare benign cartilaginous neoplasm pathognomonically defined by two exclusion criteria, namely absence of attachment to the bony cortex or periosteum and exclusion of intra-articular or tenosynovial localization (7). Soft tissue chondroma presents as a well-defined soft tissue mass and typically does not involve the underlying bone, though bone compression or erosion may occur. Plain radiographs often show characteristic ring-like or curvilinear calcifications (8). These tumors primarily affect the soft tissues of the hands and feet and, by definition, are not associated with synovial structures. Histologically, soft tissue chondromas exhibit lobulated growth patterns of mature hyaline cartilage, which are surrounded by fibrous tissue (9). In certain cases, they may show increased cellularity, myxoid changes and variable degrees of calcification (10). Accurate diagnosis can be challenging due to their rarity and nonspecific clinical presentation. In the present case, histopathological examination confirmed a diagnosis of soft tissue chondroma, a rare entity in the anterior mediastinum.

This case adds to the limited literature on mediastinal chondromas and underscores the importance of considering this differential diagnosis when encountering calcified mediastinal masses. A review of similar cases indicates that these rare tumors are generally well-circumscribed lesions and exhibit distinctive calcifications on imaging, which can aid in preoperative identification (2,5,11).

A summary of the literature was provided in Table I, which includes cases of soft tissue chondroma located in the mediastinum, as reported in English-language publications available on PubMed (https://pubmed.ncbi.nlm.nih.gov/). All of these studies involved a CT workup. Imaging, particularly CT, is essential for the diagnosis of mediastinal soft tissue chondromas (2,5,12). These tumors often appear as well-circumscribed masses with areas of calcification (a hallmark imaging feature). Fang et al (2) documented a case of a posterior mediastinal soft tissue chondroma characterized by a well-circumscribed, calcified mass with no significant enhancement on imaging (a common feature of benign soft tissue tumors) Similarly, Shrivastava et al (5) highlighted the use of CT in identifying a benign soft tissue chondroma in a 37-year-old female with a well-circumscribed, calcified mass in the anterior mediastinum. Additionally, Widdowson and Lewis-Jones (12) reported a large soft tissue chondroma in the posterior mediastinum with extensive, irregular calcifications and a well-defined border, without attachment to adjacent ribs or the spine. This case report further supported the utility of CT in differentiating these lesions from other mediastinal tumors. Based on the three previously reported cases and the present case, the CT manifestations of mediastinal chondroma may be summarized as follows. Firstly, a round or oval mass occurs in the anterior or posterior mediastinum, which may be lobulated. Secondly, well-defined margins are present. Thirdly, focal, linear, curvilinear or other irregular calcifications may be observed within the mass. Finally, no enhancement or minimal enhancement is observed on enhanced CT. In addition to mediastinal chondroma, other mediastinal masses may also present with calcification. Therefore, a differential diagnosis is required when encountering a mediastinal mass with calcified features on clinical imaging. The differential diagnosis includes thymomas, teratomas and chondrosarcomas; though these masses may present with similar imaging findings, they are treated with completely different therapeutic regimens and associated with varied prognoses (12). Calcified mediastinal tumors represent a diagnostic challenge, with various benign and malignant entities displaying distinct patterns of calcification. Common tumors with calcifications include thymomas, teratomas and post-radiation lymphomas. Thymomas often exhibit linear or septal calcifications, particularly in cases of advanced disease, while teratomas present with coarse calcifications associated with fat, bones or teeth. Calcifications in lymphomas are rare and typically occur post irradiation. Other entities, such as pericardial cysts, intrathoracic goiters and neurogenic tumors, may also present with calcifications, although less frequently. CT imaging plays a pivotal role in identifying calcifications and differentiating these tumors, while magnetic resonance imaging aids in further soft tissue characterization (13-15). This case highlights the critical role of imaging in the diagnosis and management of mediastinal chondromas. Furthermore, it underscores the importance of histopathological confirmation in ensuring accurate diagnosis and appropriate treatment.

Table I Summary of the reported cases of soft tissue chondroma located in the mediastinum.

Table I

Summary of the reported cases of soft tissue chondroma located in the mediastinum.

Author(s)/year	Patient age, years	Sex	Symptoms	Tumor location	Computed tomography imaging findings	(Refs.)
Fang et al, 2021	51	Male	Asymptomatic, incidental finding	Posterior mediastinum	Large mass with calcifications, no invasion (diameter: 3.2 cm)	(2)
Shrivastava et al, 2006	37	Female	Asymptomatic, routine checkup revealed mediastinal mass	Anterior mediastinum	Well-circumscribed, calcified mass, likely chondroma (diameter: 3.8 cm)	(5)
Widdowson and Lewis-Jones, 1988	85	Female	Mild dyspnea	Posterior mediastinum	A heavily calcified mass (diameter: 17 cm)	(12)
Present case	36	Female	Asymptomatic, incidental finding	Anterior mediastinum	Well-circumscribed mass with calcifications (diameter: 5 cm)	-

The present study has its limitations, which are worth mentioning. The absence of iodine density maps may have affected the in-depth analysis of relevant factors, thus limiting the comprehensiveness of the research results.

In conclusion, anterior mediastinal soft tissue chondroma is a rare tumor type. It is characterized by a well-defined, calcified lesion with possible slight enhancement. When encountering a mediastinal tumor with calcification, it is important to consider chondroma in the differential diagnosis. Accurate diagnosis through a combination of imaging and histopathology is essential for guiding appropriate surgical management and ensuring favorable patient outcomes. This case report contributes to the limited literature on anterior mediastinal chondromas and underscores the importance of clinical vigilance and comprehensive diagnostic evaluation in managing these rare tumors.

Acknowledgements

Not applicable.

Funding

Funding: No funding was received.

Availability of data and materials

The data generated in the present study may be requested from the corresponding author.

Authors' contributions

YZ and MP served as the principal investigators, making substantial contributions to the study design, developing the treatment plan and overseeing the analysis and interpretation of the patient's clinical data. YZ also participated in the drafting and revision of the manuscript and approved the final version. XG designed the case study, contributed to clinical decision-making and assisted with manuscript revision. MZ and CL were responsible for acquiring key medical images and confirmed the authenticity of all raw data. All authors have read and approved the final manuscript.

Ethics approval and consent to participate

This study was conducted in accordance with the principles expressed in the Declaration of Helsinki.

Patient consent for publication

The patient provided written informed consent for the publication of this case report and any accompanying images.

Competing interests

The authors declare that they have no competing interests.

References