20th June 2023

A 26-year-old man presents to his GP with a several month history of fatigue, weight loss, more recent difficulty rising from a chair due to weakness, and dysphagia to solid food.

A 26-year-old man presents to his GP with a several month history of fatigue, weight loss, more recent difficulty rising from a chair due to weakness, and dysphagia to solid food. He has no relevant past medical history, takes no regular medications, and smoked the occasional cigarette in his teens. He drinks ~21 units of alcohol per week and denies illicit drug use. Clinical examination reveals a global muscle weakness predominantly affecting his hips and shoulders. A chest x-ray is performed and demonstrates a large mediastinal mass.

What is the most likely underlying malignancy?

Select the SINGLE most appropriate option from the list below. Select ONE option only.