A 39-year-old man presented with a 1-month history of progressive chest tightness and fever, followed by dysphonia after unsuccessful anti-inflammatory treatment at a local clinic. Physical examination was unremarkable, but laboratory tests revealed mild neutrophilia (7.22x109/L), and chest CT demonstrated an irregular anterosuperior mediastinal mass (6.1x3.0x7.8 cm) exhibiting heterogeneous density, moderate enhancement and multiple small cystic areas (figure 1A–C). The mass showed partially indistinct margins with adjacent structures. Although CT showed no mediastinal lymphadenopathy, it suggested vertebral abnormalities; subsequent thoracic spine MRI confirmed T4 vertebral bone destruction and a compression fracture, accompanied by partial soft tissue mass formation (figure 1D, E). The scan also revealed the mediastinal mass, which exhibited heterogeneous, slightly prolonged T1 and slightly prolonged to prolonged T2 signals (figure 1D, arrow); contrast-enhanced imaging showed marked heterogeneous enhancement with multiple non-enhancing cystic areas (figure 1E, asterisks). Crucially, laboratory findings provided the…