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Download the article PDF: Clinical Image Challenges November 2025
Differential Diagnosis
- Thoracic aortic aneurysm
- Pericardial cyst
- Anterior mediastinal mass
- Metastatic disease
- Lipoma or liposarcoma
Diagnosis
The anteroposterior chest x-ray reveals a large, ovoid mass located just left of the midline, appearing inseparable from the mediastinum. The pulmonary hila and aortic contour remain visible, and the lateral view (not shown) confirmed a clear posterior chest, suggesting the mass is confined to the anterior mediastinum. The anterior mediastinum is located anterior to the pericardium and inferior to the clavicles.
The differential for such a mass is classically remembered by the “4 Ts”:
- Thymoma
- Teratoma/Germ Cell Tumor
- Thyroid mass
- “Terrible” Lymphoma
A contrast-enhanced chest CT is the recommended next diagnostic step. CT imaging provides superior anatomical detail, delineating the size, location, and involvement of adjacent structures—critical for determining etiology and guiding further management. Evaluation should also include assessment for possible extra-thoracic involvement, such as testicular masses in suspected germ cell tumors.
What to Look For
- Widened mediastinum or opacity in the retrosternal clear space on chest x-ray should prompt further imaging.
- History should include systemic symptoms, lymphadenopathy, and a thorough review of systems.
- Physical examination should be comprehensive, including head, neck, supraclavicular and axillary nodes, chest, abdomen, and scrotum in male patients.
Pearls for Urgent Care Management
- Emergent referral to the ED is indicated if there are signs of airway compression or superior vena cava (SVC) syndrome (e.g., facial swelling, venous distension).
- Patients with suspected airway compromise should avoid lying supine, as this may exacerbate symptoms.
- Advanced imaging (CT chest) should be arranged promptly.
- Avoid sedation, which may worsen airway obstruction in the setting of tracheal compression.
- Do not perform biopsy in the urgent care setting due to potential complications, including bleeding or airway compromise—refer to emergency or specialty care.
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