27th June 2023

A 37-year-old woman reports progressive dyspnoea over a few months. She smokes ten cigarettes a day

A 37-year-old woman reports progressive dyspnoea over a few months. She smokes ten cigarettes a day. On examination, she appears tired and there is partial ptosis, as well as muscle weakness which worsens on repetitive movement. Chest x-ray demonstrates a mediastinal mass.

Select the SINGLE most likely aetiology of the mediastinal mass given the history. Select ONE option only.