A Massive Cavernous Mediastinal Haemangioma Causing Superior Vena Cava Obstruction and Extending to the Supraclavicular Space: A Case Report.

Mediastinal haemangiomas are exceptionally rare, benign vascular tumours and account for a very small proportion of all mediastinal masses. Their symptomatology ranges from an incidental finding to significant mass-mediated compression of vital thoracic structures. We report a unique case of a massive mediastinal cavernous haemangioma with supraclavicular and axillary extension, which led to central venous obstruction. A 24-year-old man, with a childhood history of a resected supraclavicular cyst, was found to have a symptomatic right-sided heterogeneous mediastinal mass. Computed tomography (CT) angiography identified the hypervascular mass extending from the anterior mediastinum to the supraclavicular fossa, which caused aneurysmal dilatation of the superior vena cava (SVC), with an extensive collateral venous network. Magnetic resonance imaging (MRI) appearance was highly suggestive of a haemangioma, with three interconnecting regions of sizes 7.5 × 6 cm, 9 × 5 cm, and 8.5 × 1.6 cm. The mass was histologically confirmed by transthoracic needle biopsy as a cavernous haemangioma. Due to signs of venous-phase extravasation into the mediastinum and worsening SVC diameter, embolisation was recommended after a comprehensive multidisciplinary meeting. Our radiopathologic case highlights the diagnostic intricacies of differentiating extremely bulky, but benign, haemangiomas from aggressive mediastinal malignancies. Although surgical excision is the gold standard, the involvement of critical structures, like the SVC, necessitates multidisciplinary discussion and consideration of alternative treatment approaches.