A female with dry cough, progressive dyspnoea and weight loss

A 43-yr-old Chinese female presented with dry cough, weight loss of 2 kg, and progressive breathlessness of 1 month duration. Her symptoms progressed despite two courses of oral antibiotics (a macrolide and a β-lactam) and traditional Chinese medication. There was no fever, wheeze, haemoptysis or chest discomfort. She was a life-long nonsmoker and worked in an office environment with no known exposures to chemicals, fumes or dust. She had not travelled out of Singapore for 1 yr. The only past medical history of note was that of mild asthma, which had been in remission for 10 yrs. On physical examination, there was no fever, clubbing, skin lesions, cervical lymphadenopathy or joint swelling. Auscultation of the lungs revealed crepitations with diminished breath sounds over the posterior right chest. Cardiovascular, abdominal and neurological system examinations were unremarkable. The initial chest radiograph (fig. 1⇓) and computerised tomographic (CT) scan of the thorax (fig. 2⇓) are as shown. Full blood count on three separate days showed normal total white cell count and normal differential count. The erythrocyte sedimentation rate was 75 mm·h−1. The renal function was normal. The tuberculin skin test was negative. Fine needle aspiration of the lung lesion was performed …