A 76-year-old man with no significant past medical history presented with a two month history of progressive shortness of breath, 25-pound weight loss, and sharp right-sided chest, abdomen, and pelvic pain without radiation. The patient noted his dyspnea became more pronounced in recent weeks, notably worse with climbing stairs or performing work around the house. He described the pain as having a positional component, and exacerbated with deep-inspiration. On further questioning, the patient reported a 50-pack-year history of smoking and past exposure to asbestos while working with heating insulation. Physical examination revealed an age-appropriate, but cachectic appearing male with tenderness of the right abdomen to palpation, mild tachypnea with 95% oxygen saturation on two liters of oxygen, and normal cardiac rate and rhythm. Initial chest radiograph revealed a large mass causing near complete opacification of the right hemithorax (Figure 1) which was a new finding compared to the patient’s previous chest radiograph two years prior (Figure 2). Computed tomography (CT) scan of the chest/abdomen/pelvis performed to further evaluate this mass (Figure 3) revealed a 20 x 21 x 23 cm heterogeneous tumor above the right hemidiaphragm with extension into the left atrium via the right pulmonary vein (white arrow), as well as lateral and anterior diaphragmatic and pleural involvement. Differential diagnosis at this stage included malignant mass, benign pleural wall tumor, and mesothelioma. Pathology from surgical biopsy (Figure 4) suggested Sarcomatoid mesothelioma.