Mediastinal Masses

A 52-year-old man with a 15-year history of myasthenia gravis presents with progressive dyspnea and chest discomfort. Chest X-ray shows a well-defined, homogeneous anterior mediastinal mass measuring 8 cm. CT chest reveals a mass with a smooth border, mild heterogeneity, and no evidence of invasion into adjacent structures. The mass shows mild enhancement on contrast administration. Serum tumor markers (AFP, beta-hCG) are negative. What is the most likely diagnosis?

A 28-year-old woman presents with a 3-month history of progressive dyspnea, chest pain, and a dry cough. She reports no fever or weight loss. On examination, she has mild dyspnea at rest and reduced breath sounds bilaterally. Chest X-ray shows a large anterior mediastinal mass with displacement of the trachea to the right and compression of the left main bronchus. CT chest reveals a heterogeneous mass with areas of necrosis and hemorrhage. Serum beta-hCG and alpha-fetoprotein are both elevated. What is the most likely diagnosis?

A 52-year-old man with a 30-year smoking history presents with progressive dyspnea and chest pain. Chest X-ray shows a well-defined, smooth anterior mediastinal mass. CT chest demonstrates a homogeneous mass with mild enhancement, and there is no evidence of calcification or fat planes. The patient reports intermittent fever and night sweats. Serum LDH is markedly elevated at 2400 U/L. Tumor markers (β-hCG and α-fetoprotein) are normal. What is the most likely diagnosis?

A 35-year-old woman presents with progressive dyspnea, chest pain, and superior vena cava syndrome. Chest X-ray shows a large anterior mediastinal mass. CT chest reveals a heterogeneous mass with areas of low attenuation and calcification. Laboratory investigations show elevated LDH (1200 U/L), elevated β-hCG (450 mIU/mL), and normal α-fetoprotein. What is the most likely diagnosis?